1.
Taxonomy (biology)
–
Taxonomy is the science of defining groups of biological organisms on the basis of shared characteristics and giving names to those groups. The exact definition of taxonomy varies from source to source, but the core of the remains, the conception, naming. There is some disagreement as to whether biological nomenclature is considered a part of taxonomy, the broadest meaning of taxonomy is used here. The word taxonomy was introduced in 1813 by Candolle, in his Théorie élémentaire de la botanique, the term alpha taxonomy is primarily used today to refer to the discipline of finding, describing, and naming taxa, particularly species. In earlier literature, the term had a different meaning, referring to morphological taxonomy, ideals can, it may be said, never be completely realized. They have, however, a value of acting as permanent stimulants. Some of us please ourselves by thinking we are now groping in a beta taxonomy, turrill thus explicitly excludes from alpha taxonomy various areas of study that he includes within taxonomy as a whole, such as ecology, physiology, genetics, and cytology. He further excludes phylogenetic reconstruction from alpha taxonomy, thus, Ernst Mayr in 1968 defined beta taxonomy as the classification of ranks higher than species. This activity is what the term denotes, it is also referred to as beta taxonomy. How species should be defined in a group of organisms gives rise to practical and theoretical problems that are referred to as the species problem. The scientific work of deciding how to define species has been called microtaxonomy, by extension, macrotaxonomy is the study of groups at higher taxonomic ranks, from subgenus and above only, than species. While some descriptions of taxonomic history attempt to date taxonomy to ancient civilizations, earlier works were primarily descriptive, and focused on plants that were useful in agriculture or medicine. There are a number of stages in scientific thinking. Early taxonomy was based on criteria, the so-called artificial systems. Later came systems based on a complete consideration of the characteristics of taxa, referred to as natural systems, such as those of de Jussieu, de Candolle and Bentham. The publication of Charles Darwins Origin of Species led to new ways of thinking about classification based on evolutionary relationships and this was the concept of phyletic systems, from 1883 onwards. This approach was typified by those of Eichler and Engler, the advent of molecular genetics and statistical methodology allowed the creation of the modern era of phylogenetic systems based on cladistics, rather than morphology alone. Taxonomy has been called the worlds oldest profession, and naming and classifying our surroundings has likely been taking place as long as mankind has been able to communicate
2.
Bacteria
–
Bacteria constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods, Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, Bacteria also live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, and only half of the bacterial phyla have species that can be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology, There are typically 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water. There are approximately 5×1030 bacteria on Earth, forming a biomass which exceeds that of all plants, Bacteria are vital in many stages of the nutrient cycle by recycling nutrients such as the fixation of nitrogen from the atmosphere. The nutrient cycle includes the decomposition of bodies and bacteria are responsible for the putrefaction stage in this process. In March 2013, data reported by researchers in October 2012, was published and it was suggested that bacteria thrive in the Mariana Trench, which with a depth of up to 11 kilometres is the deepest known part of the oceans. Other researchers reported related studies that microbes thrive inside rocks up to 580 metres below the sea floor under 2.6 kilometres of ocean off the coast of the northwestern United States. According to one of the researchers, You can find microbes everywhere—theyre extremely adaptable to conditions, the vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, though many are beneficial particularly in the gut flora. However several species of bacteria are pathogenic and cause diseases, including cholera, syphilis, anthrax, leprosy. The most common fatal diseases are respiratory infections, with tuberculosis alone killing about 2 million people per year. In developed countries, antibiotics are used to treat infections and are also used in farming, making antibiotic resistance a growing problem. Once regarded as constituting the class Schizomycetes, bacteria are now classified as prokaryotes. Unlike cells of animals and other eukaryotes, bacterial cells do not contain a nucleus and these evolutionary domains are called Bacteria and Archaea. The ancestors of modern bacteria were unicellular microorganisms that were the first forms of life to appear on Earth, for about 3 billion years, most organisms were microscopic, and bacteria and archaea were the dominant forms of life. In 2008, fossils of macroorganisms were discovered and named as the Francevillian biota, however, gene sequences can be used to reconstruct the bacterial phylogeny, and these studies indicate that bacteria diverged first from the archaeal/eukaryotic lineage. Bacteria were also involved in the second great evolutionary divergence, that of the archaea, here, eukaryotes resulted from the entering of ancient bacteria into endosymbiotic associations with the ancestors of eukaryotic cells, which were themselves possibly related to the Archaea
3.
Firmicutes
–
The Firmicutes are a phylum of bacteria, most of which have Gram-positive cell wall structure. A few, however, such as Megasphaera, Pectinatus, Selenomonas and they have round cells, called cocci, or rod-like forms. Many Firmicutes produce endospores, which are resistant to desiccation and can survive extreme conditions and they are found in various environments, and the group includes some notable pathogens. Those in one family, the heliobacteria, produce energy through photosynthesis, Firmicutes play an important role in beer, wine, and cider spoilage. The group is divided into the Clostridia, which are anaerobic, the Bacilli, which are obligate or facultative aerobes. On phylogenetic trees, the first two show up as paraphyletic or polyphyletic, as do their main genera, Clostridium. The division Firmicutes as part of the gut flora has been shown to be involved in energy resorption, presence of Christensenella, in class Clostridia and also isolated from human faeces, has been found to correlate with lower body mass index. The presence of Firmicutes can be detected with polymerase chain reaction techniques. Phylum Firmicutes - J. P. Euzéby, List of Prokaryotic names with Standing in Nomenclature
4.
Bacilli
–
Bacilli refers to a taxonomic class of bacteria. It includes two orders, Bacillales and Lactobacillales, which contain several well-known pathogens such as Bacillus anthracis, several related concepts make use of similar words, and the ambiguity can create considerable confusion. The term Bacillus is also the name of a genus that, among other genera. Also, bacillus can be a term to describe the morphology of any rod-shaped bacterium. This general term does not mean that the subject is a member of class Bacilli or genus Bacillus, thus, it does not necessarily imply a similar group of characteristics. Not all members of class Bacilli are rod-shaped, and many other rod-shaped bacteria that do not fall within that class exist, moreover, the general term bacillus does not necessarily indicate the Gram-positive staining common to class Bacilli. For example, E. coli is a bacterium that could, therefore, be described as a bacillus. Some microbiologists have forsaken the general term because of the confusion it can create
5.
Bacillaceae
–
The Bacillaceae are a family of Gram-positive, heterotrophic, rod-shaped bacteria that may produce endospores. Motile members of family are characterized by peritrichous flagella. Some Bacillaceae are aerobic, while others are facultative or strict anaerobes, most are not pathogenic, but Bacillus species are known to cause disease in humans. Some Bacillaceae, such as the genera Filobacillus, Lentibacillus, and Halobacillus, stain Gram-negative or Gram-variable, genera within this family are sometimes colloquially identified as bacilli. However, this term is a misnomer because it does not distinguish between class Bacilli, order Bacillales, family Bacillaceae, and genus Bacillus
6.
Bacillus
–
Bacillus is a genus of gram-positive, rod-shaped bacteria and a member of the phylum Firmicutes. Bacillus species can be obligate aerobes, or facultative anaerobes and they will test positive for the enzyme catalase when there has been oxygen used or present. Ubiquitous in nature, Bacillus includes both free-living and parasitic pathogenic species and these characteristics originally defined the genus, but not all such species are closely related, and many have been moved to other genera of the Firmicutes. Many species of Bacillus can produce copious amounts of enzymes which are use of in different industries. B. subtilis has proved a model for research. Other species of Bacillus are important pathogens, causing anthrax and food poisoning, many Bacillus species are able to secrete large quantities of enzymes. A portion of the Bacillus thuringiensis genome was incorporated into corn crops, the resulting GMOs are therefore resistant to some insect pests. Bacillus subtilis is one of the best understood prokaryotes, in terms of molecular and cellular biology and its superb genetic amenability and relatively large size have provided the powerful tools required to investigate a bacterium from all possible aspects. Recent improvements in fluorescent microscopy techniques have provided insight into the dynamic structure of a single cell organism. Bacillus species are almost ubiquitous in nature, e. g. in soil, B. thuringiensis produces a toxin that can kill insects and thus has been used as insecticide. Two Bacillus species are considered significant, B. anthracis, which causes anthrax, and B. cereus. A third species, B. thuringiensis, is an important insect pathogen, the type species is B. subtilis, an important model organism. It is also a notable food spoiler, causing ropiness in bread, some environmental and commercial strains of B. coagulans may play a role in food spoilage of highly acidic, tomato-based products. An easy way to isolate Bacillus species is by placing nonsterile soil in a test tube with water, shaking, placing in melted mannitol salt agar, colonies are usually large, spreading, and irregularly shaped. Under the microscope, the Bacillus cells appear as rods, the cell wall is composed of teichoic and teichuronic acids. The role of the cytoskeleton in shape generation and maintenance is important The genus Bacillus was named in 1835 by Christian Gottfried Ehrenberg and he had seven years earlier named the genus Bacterium. Bacillus was later amended by Ferdinand Cohn to further describe them as spore-forming, Gram-positive, like other genera associated with the early history of microbiology, such as Pseudomonas and Vibrio, the 266 species of Bacillus are ubiquitous. The genus has a very large ribosomal 16S diversity and is environmentally diverse, several studies have tried to reconstruct the phylogeny of the genus
7.
Binomial nomenclature
–
Such a name is called a binomial name, a binomen, binominal name or a scientific name, more informally it is also called a Latin name. The first part of the name identifies the genus to which the species belongs, for example, humans belong to the genus Homo and within this genus to the species Homo sapiens. The formal introduction of system of naming species is credited to Carl Linnaeus. But Gaspard Bauhin, in as early as 1623, had introduced in his book Pinax theatri botanici many names of genera that were adopted by Linnaeus. Although the general principles underlying binomial nomenclature are common to these two codes, there are differences, both in the terminology they use and in their precise rules. Similarly, both parts are italicized when a binomial name occurs in normal text, thus the binomial name of the annual phlox is now written as Phlox drummondii. In scientific works, the authority for a name is usually given, at least when it is first mentioned. In zoology Patella vulgata Linnaeus,1758, the original name given by Linnaeus was Fringilla domestica, the parentheses indicate that the species is now considered to belong in a different genus. The ICZN does not require that the name of the person who changed the genus be given, nor the date on which the change was made, in botany Amaranthus retroflexus L. – L. is the standard abbreviation used in botany for Linnaeus. – Linnaeus first named this bluebell species Scilla italica, Rothmaler transferred it to the genus Hyacinthoides, the ICN does not require that the dates of either publication be specified. Prior to the adoption of the binomial system of naming species. Together they formed a system of polynomial nomenclature and these names had two separate functions. First, to designate or label the species, and second, to be a diagnosis or description, such polynomial names may sometimes look like binomials, but are significantly different. For example, Gerards herbal describes various kinds of spiderwort, The first is called Phalangium ramosum, Branched Spiderwort, is aptly termed Phalangium Ephemerum Virginianum, Soon-Fading Spiderwort of Virginia. The Latin phrases are short descriptions, rather than identifying labels, the Bauhins, in particular Caspar Bauhin, took some important steps towards the binomial system, by pruning the Latin descriptions, in many cases to two words. The adoption by biologists of a system of binomial nomenclature is due to Swedish botanist and physician Carl von Linné. It was in his 1753 Species Plantarum that he first began using a one-word trivial name together with a generic name in a system of binomial nomenclature. This trivial name is what is now known as an epithet or specific name
8.
Etiology
–
Etiology is the study of causation, or origination. The word is derived from the Greek αἰτιολογία, aitiologia, giving a reason for, an etiological myth is a myth intended to explain a name or create a mythic history for a place or family, an origin story. In medicine, etiology refers to the many factors coming together to cause an illness and it is normally the focus of epidemiological studies. The etiology of scurvy is a good example, with scurvy, sailors going to sea often lacked fresh vegetables. Without knowing the cause, Captain James Cook suspected scurvy was caused by the lack of vegetables in the diet. It was only two centuries later, in 1926, that it was discovered that it was the lack of vitamin C in a sailors diet that was the basic cause of scurvy. From modern knowledge we can see that the sauerkraut was probably much less effective than Cook supposed, an etiological myth, or origin myth, is a myth intended to explain the origins of cult practices, natural phenomena, proper names and the like. While Delphi is actually related to the word delphus, many myths are similarly based on folk etymology. In the Aeneid, Virgil claims the descent of Augustus Caesars Julian clan from the hero Aeneas through his son Ascanius, also called Iulus. In Ovids Pyramus and Thisbe, the origin of the color of mulberries is explained, backstory Bradford Hill criteria Creation myth Just-so story Just So Stories Pathology The dictionary definition of etiology at Wiktionary
9.
Gram-positive bacteria
–
Gram-positive bacteria are bacteria that give a positive result in the Gram stain test. Gram-positive bacteria take up the crystal violet stain used in the test and this is because the thick peptidoglycan layer in the bacterial cell wall retains the stain after it is washed away from the rest of the sample, in the decolorization stage of the test. Their peptidoglycan layer is thinner and sandwiched between an inner cell membrane and a bacterial outer membrane, causing them to take up the counterstain. Despite their thicker peptidoglycan layer, gram-positive bacteria are more receptive to antibiotics than gram-negative, peptidoglycan chains are cross-linked to form rigid cell walls by a bacterial enzyme DD-transpeptidase. A much smaller volume of periplasm than that in gram-negative bacteria, only some species have a capsule usually consisting of polysaccharides. Also only some species are flagellates, and when they do have flagella they only have two basal body rings to support them, both gram-positive and gram-negative bacteria commonly have a surface layer called an S-layer. In gram-positive bacteria, the S-layer is attached to the peptidoglycan layer, specific to gram-positive bacteria is the presence of teichoic acids in the cell wall. Some of these are lipoteichoic acids, which have a component in the cell membrane that can assist in anchoring the peptidoglycan. Along with cell shape, Gram staining is a method used to differentiate bacterial species. Historically, the kingdom Monera was divided into four divisions based primarily on Gram staining, based on molecular studies of the 16S sequences, Woese recognised twelve bacterial phyla. Two of these were both gram-positive and were divided on the proportion of the guanine and cytosine content in their DNA, the high G + C phylum was made up of the Actinobacteria and the low G + C phylum contained the Firmicutes. The Actinobacteria include the Corynebacterium, Mycobacterium, Nocardia and Streptomyces genera, the Firmicutes, have a 45–60% GC content, but this is lower than that of the Actinobacteria. The gram-positive and gram-negative staining response is not a reliable characteristic as these two kinds of bacteria do not form phylogenetic coherent groups. All gram-positive bacteria are bounded by a lipid membrane, and, in general. For the bacterial cells bounded by a cell membrane, the term monoderm bacteria or monoderm prokaryotes has been proposed. The presence of inner and outer cell membranes defines a new compartment in these cells and these bacteria have been designated as diderm bacteria. The distinction between the monoderm and diderm bacteria is supported by conserved signature indels in a number of important proteins, of these two structurally distinct groups of bacteria, monoderms are indicated to be ancestral. In general, gram-positive bacteria are monoderms and have a lipid bilayer whereas gram-negative bacteria are diderms and have two bilayers
10.
Endospore
–
An endospore is a dormant, tough, and non-reproductive structure produced by certain bacteria from the Firmicute phylum. The name endospore is suggestive of a spore or seed-like form and it is a stripped-down, dormant form to which the bacterium can reduce itself. Endospore formation is triggered by a lack of nutrients. In endospore formation, the bacterium divides within its cell wall, one side then engulfs the other. Endospores enable bacteria to lie dormant for extended periods, even centuries, revival of spores millions of years old has been claimed. When the environment becomes more favorable, the endospore can reactivate itself to the vegetative state, most types of bacteria cannot change to the endospore form. Examples of bacteria that can form endospores include Bacillus and Clostridium, the endospore consists of the bacteriums DNA, ribosomes and large amounts of dipicolinic acid. Dipicolinic acid is a chemical that appears to help in the ability for endospores to maintain dormancy. This chemical comprises up to 10% of the dry weight. They are resistant to radiation, desiccation, high temperature, extreme freezing. Thermo-resistant endospores were first hypothesized by Ferdinand Cohn after studying Bacillus subtilis growth on cheese after boiling the cheese and his notion of spores being the reproductive mechanism for the growth was a large blow to the previous suggestions of spontaneous generation. Astrophysicist Steinn Sigurdsson said There are viable bacterial spores that have found that are 40 million years old on Earth –. Common anti-bacterial agents that work by destroying vegetative cell walls do not affect endospores, endospores are commonly found in soil and water, where they may survive for long periods of time. A variety of different microorganisms form spores or cysts, but the endospores of low G+C gram-positive bacteria are by far the most resistant to harsh conditions, some classes of bacteria can turn into exospores, also known as microbial cysts, instead of endospores. Exospores and endospores are two kinds of hibernating or dormant stages seen in classes of microorganisms. Bacteria produce a single endospore internally, the spore is sometimes surrounded by a thin covering known as the exosporium, which overlies the spore coat. The spore coat, which acts like a sieve that excludes large toxic molecules like lysozyme, is resistant to many toxic molecules, the cortex lies beneath the spore coat and consists of peptidoglycan. The core wall lies beneath the cortex and surrounds the protoplast or core of the endospore, the core contains the spore chromosomal DNA which is encased in chromatin-like proteins known as SASPs, that protect the spore DNA from UV radiation and heat
11.
Bacterium
–
Bacteria constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods, Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, Bacteria also live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, and only half of the bacterial phyla have species that can be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology, There are typically 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water. There are approximately 5×1030 bacteria on Earth, forming a biomass which exceeds that of all plants, Bacteria are vital in many stages of the nutrient cycle by recycling nutrients such as the fixation of nitrogen from the atmosphere. The nutrient cycle includes the decomposition of bodies and bacteria are responsible for the putrefaction stage in this process. In March 2013, data reported by researchers in October 2012, was published and it was suggested that bacteria thrive in the Mariana Trench, which with a depth of up to 11 kilometres is the deepest known part of the oceans. Other researchers reported related studies that microbes thrive inside rocks up to 580 metres below the sea floor under 2.6 kilometres of ocean off the coast of the northwestern United States. According to one of the researchers, You can find microbes everywhere—theyre extremely adaptable to conditions, the vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, though many are beneficial particularly in the gut flora. However several species of bacteria are pathogenic and cause diseases, including cholera, syphilis, anthrax, leprosy. The most common fatal diseases are respiratory infections, with tuberculosis alone killing about 2 million people per year. In developed countries, antibiotics are used to treat infections and are also used in farming, making antibiotic resistance a growing problem. Once regarded as constituting the class Schizomycetes, bacteria are now classified as prokaryotes. Unlike cells of animals and other eukaryotes, bacterial cells do not contain a nucleus and these evolutionary domains are called Bacteria and Archaea. The ancestors of modern bacteria were unicellular microorganisms that were the first forms of life to appear on Earth, for about 3 billion years, most organisms were microscopic, and bacteria and archaea were the dominant forms of life. In 2008, fossils of macroorganisms were discovered and named as the Francevillian biota, however, gene sequences can be used to reconstruct the bacterial phylogeny, and these studies indicate that bacteria diverged first from the archaeal/eukaryotic lineage. Bacteria were also involved in the second great evolutionary divergence, that of the archaea, here, eukaryotes resulted from the entering of ancient bacteria into endosymbiotic associations with the ancestors of eukaryotic cells, which were themselves possibly related to the Archaea
12.
Growth medium
–
A growth medium or culture medium is a solid or liquid or semi-solid designed to support the growth of microorganisms or cells, or small plants like the moss Physcomitrella patens. Different types of media are used for growing different types of cells, the most common growth media for microorganisms are nutrient broths and agar plates, specialized media are sometimes required for microorganism and cell culture growth. Some organisms, termed fastidious organisms, require specialized environments due to nutritional requirements. Viruses, for example, are intracellular parasites and require a growth medium containing living cells. The most common media for microorganisms are nutrient broths or LB medium. Liquid media are often mixed with agar and poured via a media dispenser into Petri dishes to solidify. These agar plates provide a medium on which microbes may be cultured. They remain solid, as very few bacteria are able to decompose agar, bacteria grown in liquid cultures often form colloidal suspensions. In the case of cells, this difficulty is often addressed by the addition of blood serum or a synthetic serum replacement to the medium. In the case of microorganisms, no such limitations exist, as they are often unicellular organisms. One other major difference is that cells in culture are often grown on a flat surface to which they attach, and the medium is provided in a liquid form. In contrast, bacteria such as Escherichia coli may be grown on solid or in liquid media, an important distinction between growth media types is that of defined versus undefined media. A defined medium will have known quantities of all ingredients, for microorganisms, they consist of providing trace elements and vitamins required by the microbe and especially defined carbon and nitrogen sources. Glucose or glycerol are used as carbon sources, and ammonium salts or nitrates as inorganic nitrogen sources. An undefined medium has some complex ingredients, such as yeast extract or casein hydrolysate, undefined media are sometimes chosen based on price and sometimes by necessity – some microorganisms have never been cultured on defined media. A good example of a medium is the wort used to make beer. The wort contains all the nutrients required for yeast growth, and under anaerobic conditions, when the fermentation process is complete, the combination of medium and dormant microbes, now beer, is ready for consumption. Minimal media can also be used to select for or against recombinants or exconjugants and this supplementation allows for the culturing of specific lines of auxotrophic recombinants
13.
Cellular respiration
–
Respiration is one of the key ways a cell releases chemical energy to fuel cellular activity. Cellular respiration is considered an exothermic reaction which releases heat. The overall reaction occurs in a series of steps, most of which are redox reactions themselves. Nutrients that are used by animal and plant cells in respiration include sugar, amino acids and fatty acids. The chemical energy stored in ATP can then be used to drive processes requiring energy, including biosynthesis, aerobic respiration requires oxygen in order to create ATP. The potential of NADH and FADH2 is converted to more ATP through a transport chain with oxygen as the terminal electron acceptor. Most of the ATP produced by cellular respiration is made by oxidative phosphorylation. This works by the released in the consumption of pyruvate being used to create a chemiosmotic potential by pumping protons across a membrane. This potential is used to drive ATP synthase and produce ATP from ADP. Biology textbooks often state that 38 ATP molecules can be made per oxidised glucose molecule during cellular respiration, aerobic metabolism is up to 15 times more efficient than anaerobic metabolism. They share the pathway of glycolysis but aerobic metabolism continues with the Krebs cycle. The post-glycolytic reactions take place in the mitochondria in eukaryotic cells, glycolysis is a metabolic pathway that takes place in the cytosol of cells in all living organisms. This pathway can function with or without the presence of oxygen, in humans, aerobic conditions produce pyruvate and anaerobic conditions produce lactate. In aerobic conditions, the process converts one molecule of glucose into two molecules of pyruvate, generating energy in the form of two net molecules of ATP, four molecules of ATP per glucose are actually produced, however, two are consumed as part of the preparatory phase. The initial phosphorylation of glucose is required to increase the reactivity in order for the molecule to be cleaved into two molecules by the enzyme aldolase. During the pay-off phase of glycolysis, four groups are transferred to ADP by substrate-level phosphorylation to make four ATP. Glycogen can be converted into glucose 6-phosphate as well with the help of glycogen phosphorylase, during energy metabolism, glucose 6-phosphate becomes fructose 6-phosphate. An additional ATP is used to phosphorylate fructose 6-phosphate into fructose 1, fructose 1, 6-diphosphate then splits into two phosphorylated molecules with three carbon chains which later degrades into pyruvate
14.
Anaerobic respiration
–
Anaerobic respiration is respiration using electron acceptors other than oxygen. Although oxygen is not used as the electron acceptor, the process still uses a respiratory electron transport chain called physolmere. Kalim In aerobic organisms undergoing respiration, electrons are shuttled to a transport chain. Molecular oxygen is an oxidizing agent and, therefore, is an excellent acceptor. In anaerobes, other less-oxidizing substances such as sulfate, nitrate, sulphur and these terminal electron acceptors have smaller reduction potentials than O2, meaning that less energy is released per oxidized molecule. Anaerobic respiration is, therefore, in general energetically less efficient than aerobic respiration, anaerobic respiration is used mainly by bacteria and archaea that live in environments devoid of oxygen. Many anaerobic organisms are obligate anaerobes meaning that they can respire only using anaerobic compounds, a proton motive force or pmf drives protons down the gradient through the proton channel of ATP synthase. The resulting current drives ATP synthesis from ADP and inorganic phosphate, fermentation, in contrast, does not utilize an electrochemical gradient. Fermentation instead only uses substrate-level phosphorylation to produce ATP, the electron acceptor NAD+ is regenerated from NADH formed in oxidative steps of the fermentation pathway by the reduction of oxidized compounds. These oxidized compounds are formed during the fermentation pathway itself. In yeast, acetaldehyde is reduced to ethanol to regenerate NAD+, the two processes thus generate ATP in very different ways, and the terms should not be treated as synonyms. Anaerobic respiration is a component of the global nitrogen, iron, sulfur, and carbon cycles through the reduction of the oxyanions of nitrogen, sulfur. The biogeochemical cycling of these compounds, which depends upon anaerobic respiration, significantly impacts the carbon cycle, anaerobic respiration occurs in many environments, including freshwater and marine sediments, soil, subsurface aquifers, deep subsurface environments, and biofilms. Even environments, such as soil, that contain oxygen also have micro-environments that lack oxygen due to the slow diffusion characteristics of oxygen gas, another example is methanogenesis, a form of carbonate respiration, that is used to produce methane gas by anaerobic digestion. Biogenic methane is used as an alternative to fossil fuels. On the negative side, uncontrolled methanogenesis in landfill sites releases large volumes of methane into the atmosphere, dissimilatory denitrification is widely used in the removal of nitrate and nitrite from municipal wastewater. An excess of nitrate can lead to eutrophication of waterways into which treated water is released, elevated nitrite levels in drinking water can lead to problems due to its toxicity. Denitrification converts both compounds into harmless nitrogen gas, for example, toxic arsenate or selenate can be reduced to less toxic compounds by various anaerobic bacteria via anaerobic respiration
15.
Bacterial capsule
–
The cell capsule is a very large structure of some prokaryotic cells, such as bacterial cells. It is a layer that lies outside the cell envelope of bacteria. It is a layer, not easily washed off. When the amorphous viscid secretion diffuses into the medium and remains as a loose undemarcated secretion. It usually consists of polysaccharides, but can be composed of materials, also peptidoglycan. Because most capsules are so packed, they are difficult to stain using standard stains because most stains cannot adhere to the capsule. For examination under the microscope, the bacteria and their background are stained darker than the capsule, which doesnt stain. When viewed, bacterial cells as well as the surface they are on, are stained dark, while the capsule remains pale or colorless and appears as a ring, or halo, the capsule is considered a virulence factor because it enhances the ability of bacteria to cause disease. The capsule can protect cells from engulfment by eukaryotic cells, such as macrophages, a capsule-specific antibody may be required for phagocytosis to occur. Capsules also contain water which protects the bacteria against desiccation and they also exclude bacterial viruses and most hydrophobic toxic materials such as detergents. Immunity to one type does not result in immunity to the other types. Capsules also help cells adhere to surfaces, Streptococcus pyogenes synthesizes a hyaluronic acid capsule. Streptococcus pneumoniae has at least 91 different capsular serotypes and these serotypes are the basis for the pneumococcal vaccines. Streptococcus agalactiae produces a capsule of nine antigenic types that all contain sialic acid. Staphylococcus epidermidis The yeast Cryptococcus neoformans, though not a bacterium, has a similar capsule, capsules too small to be seen with an ordinary microscope, such as the M protein of Streptococcus pyogenes, are called microcapsules. India ink staining, the capsule appears as a halo around the bacterium as the ink cant penetrate the capsule. Manevals capsule stain, the capsule appears as a clear halo between the bacterium and the bluish-grey stained background. The background stain is the acidic stain Congo red, and the stain is acid fuschin
16.
Bordetella pertussis
–
Bordetella pertussis is a Gram-negative, aerobic, pathogenic, encapsulated coccobacillus of the genus Bordetella, and the causative agent of pertussis or whooping cough. Unlike B. bronchiseptica, B. pertussis is not motile and its virulence factors include pertussis toxin, filamentous hæmagglutinin, pertactin, fimbria, and tracheal cytotoxin. The bacterium is spread by airborne droplets, its period is to human whooping cough in average 9–10 days. Humans are the only known reservoir for B. pertussis, the complete B. pertussis genome of 4,086,186 base pairs was published in 2003. Pertussis is an infection of the respiratory system characterized by a sound when the person breathes in. In the US, it killed between 10,000 and 20,000 people per year before a vaccine was available, vaccination has transformed this, between 1985 and 1988, fewer than 100 children died from pertussis. Worldwide in 2000, according to the WHO, around 39 million people were infected annually, a graph is available showing the dramatic effect of introducing vaccination in England. B. pertussis infects its host by colonizing lung epithelial cells, the bacterium contains a surface protein, filamentous haemagglutinin adhesin, which binds to the sulfatides found on cilia of epithelial cells. Once anchored, the bacterium produces tracheal cytotoxin, which stops the cilia from beating and this prevents the cilia from clearing debris from the lungs, so the body responds by sending the host into a coughing fit. These coughs expel some bacteria into the air, which are free to infect other hosts, B. pertussis has the ability to inhibit the function of the hosts immune system. The toxin, known as pertussis toxin, inhibits G protein coupling that regulates an adenylate cyclase-mediated conversion of ATP to cyclic AMP. The end result is phagocytes convert too much ATP to cyclic AMP, which can cause disturbances in cellular signaling mechanisms and this is unique in that many bacterial infections illustrate neutrophil-predominance instead. The infection occurs mostly in children under the age of one when they are unimmunized, or children with faded immunity, the signs and symptoms are similar to a common cold, runny nose, sneezing, mild cough, and low-grade fever. The patient becomes most contagious during the stage of infection. It may become airborne when the person coughs, sneezes, or laughs, pertussis vaccine is part of the diphtheria, tetanus, and acellular pertussis immunization. The paroxysmal cough precedes a crowing inspiratory sound characteristic of pertussis, after a spell, the patient might make a “whooping” sound when breathing in, or may vomit. Adults have milder symptoms, such as prolonged coughing without the “whoop”, infants less than six months also may not have the typical whoop. A coughing spell may last a minute or more, producing cyanosis, apnoea, however, when not in a coughing fit, the patient does not experience trouble breathing
17.
Calmodulin
–
Calmodulin is a multifunctional intermediate calcium-binding messenger protein expressed in all eukaryotic cells. It is a target of the secondary messenger Ca2+. Once bound to Ca2+, Calmodulin acts as part of a signal transduction pathway by modifying its interactions with various target proteins such as kinases or phosphatases. Calmodulin is a small, highly conserved protein that is 148 amino acids long, the protein has two approximately symmetrical globular domains each containing a pair of EF-hand motifs separated by a flexible linker region for a total of four Ca2+ binding sites. Each EF-hand motif allows calmodulin to sense intracellular calcium levels by binding one Ca2+ ion. Calcium ion binding regions are found in the positions in the sequence of amino acids, 21-32, 57-68, 94-105 and 130-141. These regions are located between two alpha helices in the EF-hand motifs, the first two regions are on one side of the region the other two are on the other side. Calmodulin binds such a variety of target proteins, making it especially important for it to have flexibility. Another important characteristic of calmodulin that allows it to bind a large variety of proteins is the generic shape of the non-polar grooves in the binding sites. Since the non-polar grooves are generic, they dont require the target proteins to have any specific sequence of amino acids allowing a variety of target proteins to be bound. Together, these two characteristics of calmodulin allow it to flexibly bind target proteins with various shapes and amino acid sequences. For example, calmodulin binds both NMDA receptors and potassium channels which differ in length by about 50 amino acid residues, calmodulins structure is very similar to the structure of Troponin C. They are both members of the EFh superfamily, Troponin C, like Calmodulin, has two globular domains that are connected by a linker region. However, Troponin C and Calmodulin differ in the length of the linker region and these remarkably similar structures are an example of how the EF hand motif is highly conserved in calcium binding proteins. Though they have similar structures, their functions are very different, Troponin C has a very specific function ultimately causing a contraction in skeletal muscles. Calmodulin, evolved to bind a wider variety of target proteins, up to four calcium ions are bound by calmodulin via its four EF hand motifs. EF hands supply an electronegative environment for ion coordination, after calcium binding, hydrophobic methyl groups from methionine residues become exposed on the protein via conformational change. When the alpha helices are perpendicular to one another, the Calmodulin is in an open conformation giving it a higher affinity for target proteins, more specifically, this conformational change presents hydrophobic surfaces, which can in turn bind to Basic Amphiphilic Helices on the target protein
18.
Adenylyl cyclase
–
Adenylyl cyclase is an enzyme with key regulatory roles in essentially all cells. The best known class of adenylyl cyclases is class III or AC-III, AC-III occurs widely in eukaryotes and has important roles in many human tissues. All classes of adenylyl cyclases catalyse the conversion of adenosine triphosphate to 3, 5-cyclic AMP, magnesium ions are generally required and appears to be closely involved in the enzymatic mechanism. The cAMP produced by AC then serves as a signal via specific cAMP-binding proteins, either transcription factors, enzymes. The first class of adenylyl cyclases occur in bacteria including E. coli. This was the first class of AC to be characterized and it was observed that E. coli deprived of glucose produce cAMP that serves as an internal signal to activate expression of genes for importing and metabolizing other sugars. CAMP exerts this effect by binding the transcription factor CRP, also known as CAP, Class I ACs are large cytosolic enzymes with a large regulatory domain that indirectly senses glucose levels. As of 2012, no crystal structure is available for class I AC and these adenylyl cyclases are toxins secreted by pathogenic bacteria such as Bacillus anthracis and Bordetella pertussis during infection. These bacteria also secrete proteins that enable the AC-II to enter host cells, the genes for Class II ACs are known as cyaA. Several crystal structures are known for AC-II enzymes and these adenylyl cyclases are the most familiar based on extensive study due to their important roles in human health. They are also found in bacteria, notably Mycobacterium tuberculosis where they appear to have a key role in pathogenesis. Most AC-IIIs are integral membrane proteins involved in transducing extracellular signals into intracellular responses, the effect of adrenaline is via a G protein signaling cascade, which transmits chemical signals from outside the cell across the membrane to the inside of the cell. CAMP is known as a second messenger, cyclic AMP is an important molecule in eukaryotic signal transduction, a so-called second messenger. Adenylyl cyclases are often activated or inhibited by G proteins, which are coupled to membrane receptors, photoactivatable adenylyl cyclase was discovered in E. gracilis and can be expressed in other organisms through genetic manipulation. Shining blue light on a cell containing PAC activates it and abruptly increases the rate of conversion of ATP to cAMP, for example, PAC expression in certain neurons has been shown to alter the grooming behavior in fruit flies exposed to blue light. Channelrhodopsin-2 is also used in a similar fashion, most class III adenylyl cyclases are transmembrane proteins with 12 transmembrane segments. The protein is organized with 6 transmembrane segments, then the C1 cytoplasmic domain, then another 6 membrane segments, the important parts for function are the N-terminus and the C1 and C2 regions. The C1a and C2a subdomains are homologous and form a dimer that forms the active site
19.
Anthrax toxin
–
Anthrax toxin is a three-protein exotoxin secreted by virulent strains of the bacterium, Bacillus anthracis—the causative agent of anthrax. The toxin was first discovered by Harry Smith in 1954, anthrax toxin is composed of a cell-binding protein, known as protective antigen, and two enzyme components, called edema factor and lethal factor. These three protein components act together to impart their physiological effects, assembled complexes containing the toxin components are endocytosed. In the endosome, the components of the toxin translocate into the cytoplasm of a target cell. Once in the cytosol, the components of the toxin disrupts various immune cell functions, namely cellular signaling. The toxin may even induce cell lysis, as is observed for macrophage cells, anthrax toxin allows the bacteria to evade the immune system, proliferate, and ultimately kill the host animal. Research on anthrax toxin also provides insight into the generation of assemblies, and on protein translocation, pore formation, endocytosis. Anthrax is a disease caused by Bacillus anthracis, a spore-forming, Gram positive, anthrax toxin is a mixture of three protein components, protective antigen, edema factor, and lethal factor. Each individual anthrax toxin protein is nontoxic, toxic symptoms are not observed when these proteins are injected individually into laboratory animals. The co-injection of PA and EF causes edema, and the co-injection of PA, the former combination is called edema toxin, and the latter combination is called lethal toxin. Thus the manifestation of physiological symptoms requires PA, in either case, the PA requirement observed in animal-model experiments demonstrates a common paradigm for bacterial toxins, called the A / B paradigm. The A component is enzymatically active, and the B component is the binding component. Anthrax toxin is of the form A2B, where the two enzymes, EF and LF, are the A components and PA is the B component. Thus, PA acts as a Trojan Horse, which carries EF and LF through the membrane into the cytosol. Anthrax toxin protein components must assemble into holotoxin complexes to function, in order for LF and EF to function inside a target cell, they must localize to the cell and enter its cytoplasm. Through a series of steps, PA can translocate EF and LF into the cell and this process starts when the 83-kDa form of PA, called PA83, binds to an anthrax toxin receptor. There are two known homologous receptors, which bind to PA83, called tumor endothelium marker-8 and capillary morphogenesis protein 2, then a 20 kDa fragment is cleaved off PA83s amino terminus by membrane endoproteases from the furin family. When PA20 dissociates, the remaining portion of PA, called PA63
20.
Genotypical
–
The genotype is the part of the genetic makeup of a cell, and therefore of an organism or individual, which determines a specific characteristic of that cell/organism/individual. Genotype is one of three factors that determine phenotype, the two being inherited epigenetic factors, and non-inherited environmental factors. An example of how genotype determines a characteristic is petal color in a pea plant, the genotype of an organism is the inherited map it carries within its genetic code. Not all organisms with the same genotype look or act the way because appearance. Likewise, not all organisms that look alike necessarily have the same genotype, ones genotype differs subtly from ones genomic sequence. So typically, one refers to a genotype with regard to a particular gene of interest and, in polyploid individuals. The genetic constitution of an organism is referred to as its genotype, any given gene will usually cause an observable change in an organism, known as the phenotype. The terms genotype and phenotype are distinct for at least two reasons, To distinguish the source of an observers knowledge, genotype and phenotype are not always directly correlated. Some genes only express a phenotype in certain environmental conditions. Conversely, some phenotypes could be the result of multiple genotypes, the genotype is commonly mixed up with the phenotype which describes the end result of both the genetic and the environmental factors giving the observed expression. A simple example to illustrate genotype as distinct from phenotype is the colour in pea plants. There are three available genotypes, PP, Pp, and pp, all three have different genotypes but the first two have the same phenotype as distinct from the third. A more technical example to illustrate genotype is the single nucleotide polymorphism or SNP, a SNP occurs when corresponding sequences of DNA from different individuals differ at one DNA base, for example where the sequence AAGCCTA changes to AAGCTTA. This contains two alleles, C and T. SNPs typically have three genotypes, denoted generically AA Aa and aa, in the example above, the three genotypes would be CC, CT and TT. Other types of marker, such as microsatellites, can have more than two alleles, and thus many different genotypes. The distinction between genotype and phenotype is commonly experienced when studying family patterns for certain diseases or conditions, for example. Due to the diploidy of humans, there are two alleles for any given gene and these alleles can be the same or different, depending on the individual. With a dominant allele, the offspring is guaranteed to inherit the trait in question irrespective of the second allele, in the case of an albino with a recessive allele, the phenotype depends upon the other allele
21.
Phenotype
–
A phenotype is the composite of an organisms observable characteristics or traits, such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior. A phenotype results from the expression of a genetic code, its genotype, as well as the influence of environmental factors. When two or more clearly different phenotypes exist in the population of a species, the species is called polymorphic. A well-documented polymorphism is Labrador Retriever coloring, while the color depends on many genes, it is clearly seen in the environment as yellow, black. This genotype-phenotype distinction was proposed by Wilhelm Johannsen in 1911 to make clear the difference between an organisms heredity and what that heredity produces, the distinction is similar to that proposed by August Weismann, who distinguished between germ plasm and somatic cells. The term phenotype has sometimes incorrectly used as a shorthand for phenotypic difference from wild type. Despite its seemingly straightforward definition, the concept of the phenotype has hidden subtleties and it may seem that anything dependent on the genotype is a phenotype, including molecules such as RNA and proteins. It may seem that this goes beyond the intentions of the concept with its focus on the organism in itself. Either way, the term phenotype includes traits or characteristics that can be visible by some technical procedure. A notable extension to this idea is the presence of molecules or metabolites that are generated by organisms from chemical reactions of enzymes. Another extension adds behavior to the phenotype, since behaviors are also observable characteristics, behavioral phenotypes include cognitive, personality, and behavioral patterns. Some behavioral phenotypes may characterize psychiatric disorders or syndromes, phenotypic variation is a fundamental prerequisite for evolution by natural selection. It is the organism as a whole that contributes to the next generation. Without phenotypic variation, there would be no evolution by natural selection, the plant Hieracium umbellatum is found growing in two different habitats in Sweden. These habitats alternate along the coast of Sweden and the habitat that the seeds of Hieracium umbellatum land in, the concept of phenotype can be extended to variations below the level of the gene that affect an organisms fitness. For example, silent mutations that do not change the amino acid sequence of a gene may change the frequency of guanine-cytosine base pairs. The term extended phenotype refers to the idea that a phenotype is not restricted to biological processes, the concept generalized by Richard Dawkins explains that phenotype includes all the influence a gene has on the environment and other organisms. ”There are three types of extended phenotypes. The first describes an organism using architectural constructions to modify their environment for living, the most common example given by Dawkins is the beaver
22.
Bacillus cereus
–
Bacillus cereus is a Gram-positive, rod-shaped, aerobic, motile, beta hemolytic bacterium commonly found in soil and food. Some strains are harmful to humans and cause illness, while other strains can be beneficial as probiotics for animals. It is the cause of fried rice syndrome, as the bacteria are classically contracted from fried rice dishes that have been sitting at room temperature for hours, B. cereus bacteria are facultative anaerobes, and like other members of the genus Bacillus, can produce protective endospores. Its virulence factors include cereolysin and phospholipase C and it was from this species that two new enzymes, named AlkC and AlkD, which are involved in DNA repair, were discovered in 2006. Colonies of Bacillus cereus were originally isolated from an agar plate left exposed to the air in a cow shed, B. cereus competes with other microorganisms such as Salmonella and Campylobacter in the gut, so its presence reduces the numbers of those microorganisms. In food animals such as chickens, rabbits and pigs, some strains of B. cereus are used as a probiotic feed additive to reduce Salmonella in the intestines. This improves the growth as well as food safety for humans who eat their meat. Some strains of B. cereus produce cereins, bacteriocins active against different B. cereus strains or other Gram-positive bacteria. At 30 °C, a population of B. cereus can double in as little as 20 minutes or as long as 3 hours, B. cereus is responsible for a minority of foodborne illnesses, causing severe nausea, vomiting, and diarrhea. Bacillus foodborne illnesses occur due to survival of the bacterial endospores when food is improperly cooked, cooking temperatures less than or equal to 100 °C allow some B. cereus spores to survive. This problem is compounded when food is then refrigerated, allowing the endospores to germinate. Cooked foods not meant for immediate consumption or rapid cooling. Germination and growth generally occur between 10 °C and 50 °C, though some strains are psychrotrophic, Bacterial growth results in production of enterotoxins, one of which is highly resistant to heat and acids, ingestion leads to two types of illness, diarrheal and emetic syndrome. The diarrheal type is associated with a range of foods, has an 8. 0- to 16-hour incubation time. Also known as the form of B. cereus food poisoning. Cereus spores within the intestine may be the cause of illness. The emetic form is caused by rice cooked for a time and temperature insufficient to kill any spores present. It can produce a toxin, cereulide, which is not inactivated by later reheating and this form leads to nausea and vomiting one to five hours after consumption
23.
Bacillus thuringiensis
–
Bacillus thuringiensis is a Gram-positive, soil-dwelling bacterium, commonly used as a biological pesticide. During sporulation, many Bt strains produce crystal proteins, called δ-endotoxins and this has led to their use as insecticides, and more recently to genetically modified crops using Bt genes, such as Bt corn. Many crystal-producing Bt strains, though, do not have insecticidal properties, B. thuringiensis was first discovered in 1901 by Japanese biologist Ishiwata Shigetane. In 1911, B. thuringiensis was rediscovered in Germany by Ernst Berliner, in 1976, Robert A. Zakharyan reported the presence of a plasmid in a strain of B. thuringiensis and suggested the plasmids involvement in endospore and crystal formation. B. thuringiensis is closely related to B. cereus, a bacterium, and B. anthracis, the cause of anthrax. Like other members of the genus, all three are aerobes capable of producing endospores, the are several dozen recognized subspecies of bacillus thuringiensis. Subspecies commonly used as insecticides include Bacillus thuringiensis subspecies kurstaki and subspecies israelensis, upon sporulation, B. thuringiensis forms crystals of proteinaceous insecticidal δ-endotoxins, which are encoded by cry genes. In most strains of B. thuringiensis, the cry genes are located on a plasmid, Cry toxins have specific activities against insect species of the orders Lepidoptera, Diptera, Coleoptera, Hymenoptera and nematodes. Thus, B. thuringiensis serves as an important reservoir of Cry toxins for production of biological insecticides, the Cry toxin is then inserted into the insect gut cell membrane, paralyzing the digestive tract and forming a pore. The insect stops eating and starves to death, live Bt bacteria may also colonize the insect which can contribute to death, the midgut bacteria of susceptible larvae may be required for B. thuringiensis insecticidal activity. In 1996 another class of proteins in Bt was discovered. Vip proteins do not share sequence homology with Cry proteins, in general do not compete for the same receptors, in 2000, a novel functional group of Cry protein, designated parasporin, was discovered from noninsecticidal B. thuringiensis isolates. The proteins of parasporin group are defined as B. thuringiensis and related bacterial parasporal proteins that are not hemolytic, as of January 2013, parasporins comprise six subfamilies. Spores and crystalline insecticidal proteins produced by B. thuringiensis have been used to control insect pests since the 1920s and are applied as liquid sprays. They are now used as specific insecticides under trade names such as DiPel, each new strain is given a unique number and registered with the U. S. The Bt tobacco was never commercialized, tobacco plants are used to test genetic modifications since they are easy to genetically and are not part of the food supply. This was the New Leaf potato, and it was removed from the market in 2001 due to lack of interest, for current crops and their acreage under cultivation, see genetically modified crops. Corn genetically modified to produce VIP was first approved in the US in 2010, in India, by 2014, more than seven million cotton farmers, occupying twenty-six million acres, had adopted Bt cotton
24.
Morphology (biology)
–
Morphology is a branch of biology dealing with the study of the form and structure of organisms and their specific structural features. This includes aspects of the appearance, i. e. external morphology, as well as the form and structure of the internal parts like bones and organs. This is in contrast to physiology, which deals primarily with function, Morphology is a branch of life science dealing with the study of gross structure of an organism or taxon and its component parts. The word morphology is from the Ancient Greek don, morphé, meaning form, among other important theorists of morphology are Lorenz Oken, Georges Cuvier, Étienne Geoffroy Saint-Hilaire, Richard Owen, Karl Gegenbaur and Ernst Haeckel. In English-speaking countries, the term molecular morphology has been used for time for describing the structure of compound molecules, such as polymers. Comparative Morphology is analysis of the patterns of the locus of structures within the plan of an organism. Functional Morphology is the study of the relationship between the structure and function of morphological features, experimental Morphology is the study of the effects of external factors upon the morphology of organisms under experimental conditions, such as the effect of genetic mutation. Anatomy is a branch of morphology that deals with the structure of organisms, most taxa differ morphologically from other taxa. Typically, closely related taxa differ much less than more distantly related ones, cryptic species are species which look very similar, or perhaps even outwardly identical, but are reproductively isolated. Conversely, sometimes unrelated taxa acquire a similar appearance as a result of convergent evolution or even mimicry, in addition, there can be morphological differences within a species, such as in Apoica flavissima where queens are significantly smaller than workers. A further problem with relying on morphological data is that what may appear, morphologically speaking, the significance of these differences can be examined through the use of allometric engineering in which one or both species are manipulated to phenocopy the other species. Invention and development of microscopy enable the observation of 3-D cell morphology with both spatial and temporal resolution. The dynamic processes of cell morphology which are controlled by a complex system play an important role in varied important biological process, such as immune. Comparative anatomy Insect morphology Morphometrics Neuromorphology Phenetics Phenotype Phenotypic plasticity Plant morphology
25.
Spore
–
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavorable conditions. Spores form part of the cycles of many plants, algae, fungi. Bacterial spores are not part of a sexual cycle but are resistant structures used for survival under unfavourable conditions, spores are usually haploid and unicellular and are produced by meiosis in the sporangium of a diploid sporophyte. Under favourable conditions the spore can develop into a new organism using mitotic division, producing a multicellular gametophyte, two gametes fuse to form a zygote which develops into a new sporophyte. This cycle is known as alternation of generations, the term spore derives from the ancient Greek word σπορά spora, meaning seed, sowing, related to σπόρος sporos, sowing, and σπείρειν speirein, to sow. Spores germinate to give rise to haploid gametophytes, while seeds germinate to give rise to diploid sporophytes, vascular plant spores are always haploid. Vascular plants are either homosporous or heterosporous, plants that are homosporous produce spores of the same size and type. Spores can be classified in several ways, In fungi and fungus-like organisms, spores are often classified by the structure in which meiosis, since fungi are often classified according to their spore-producing structures, these spores are often characteristic of a particular taxon of the fungi. Sporangiospores, spores produced by a sporangium in many such as zygomycetes. Zygospores, spores produced by a zygosporangium, characteristic of zygomycetes, ascospores, spores produced by an ascus, characteristic of ascomycetes. Basidiospores, spores produced by a basidium, characteristic of basidiomycetes, aeciospores, spores produced by an aecium in some fungi such as rusts or smuts. Urediniospores, spores produced by a uredinium in some such as rusts or smuts. Teliospores, spores produced by a telium in some such as rusts or smuts. Oospores, spores produced by an oogonium, characteristic of oomycetes, carpospores, spores produced by a carposporophyte, characteristic of red algae. Tetraspores, spores produced by a tetrasporophyte, characteristic of red algae, chlamydospores, thick-walled resting spores of fungi produced to survive unfavorable conditions. Parasitic fungal spores may be classified into internal spores, which germinate within the host, meiospores, spores produced by meiosis, they are thus haploid, and give rise to a haploid daughter cell or a haploid individual. Examples are the cells of gametophytes of seed plants found in flowers or cones. Microspores, meiospores that give rise to a male gametophyte, megaspores, meiospores that give rise to a female gametophyte
26.
Sporangium
–
A sporangium is an enclosure in which spores are formed. It can be composed of a cell or can be multicellular. All plants, fungi, and many other lineages form sporangia at some point in their life cycle, sporangia can produce spores by mitosis, but in nearly all land plants and many fungi, sporangia are the site of meiosis and produce genetically distinct haploid spores. Structure containing the spores in fungal species, in mosses, liverworts and hornworts, an unbranched sporophyte produces a single sporangium, which may be quite complex morphologically. Most non-vascular plants, as well as many lycophytes and most ferns, are homosporous, some bryophytes, most lycophytes, and some ferns are heterosporous. These plants produce microspores and megaspores, which rise to gametophytes that are functionally male or female. In some cases, both kinds of spores are produced in the sporangium, and may even develop together as part of a spore tetrad. However, in most heterosporous plants there are two kinds of sporangia, termed microsporangia and megasporangia, a few ferns and some lycophytes are heterosporous with two kinds of sporangia, as are all the seed plants. Sporangia can be terminal or lateral of stems or associated with leaves, in ferns, sporangia are typically found on the abaxial surface of the leaf and are densely aggregated into clusters called sori. Sori may be covered by a structure called an indusium, some ferns have their sporangia scattered along reduced leaf segments or along the margin of the leaf. Lycophytes, in contrast, bear their sporangia on the surface of leaves or laterally on stems. Leaves that bear sporangia are called sporophylls, if the plant is heterosporous, the sporangia-bearing leaves are distinguished as either microsporophylls or megasporophylls. In seed plants, sporangia are located within strobili or flowers. Cycads form their microsporangia on microsporophylls which are aggregated into strobili, megasporangia are formed within ovules, which are borne on megasporophylls, which are aggregated into strobili on separate plants. Conifers typically bear their microsporangia on microsporophylls aggregated into pollen strobili. Flowering plants contain microsporangia in the anthers of stamens and megasporangia inside ovules inside ovaries, in all seed plants, spores are produced by meiosis and develop into gametophytes while still inside the sporangium. Categorized based on sequence, eusporangia and leptosporangia are differentiated in the vascular plants. In a leptosporangium, found only in ferns, development involves a single cell that becomes the stalk, wall
27.
Dipicolinic acid
–
Dipicolinic acid is a chemical compound which composes 5% to 15% of the dry weight of bacterial spores. It is implicated as responsible for the resistance of the endospore. However, mutants resistant to heat but lacking dipicolinic acid have been isolated, dipicolinic acid forms a complex with calcium ions within the endospore core. This complex binds free water molecules, causing dehydration of the spore, as a result, the heat resistance of macromolecules within the core increases. The calcium-dipicolinic acid complex also functions to protect DNA from heat denaturation by inserting itself between the nucleobases, thereby increasing the stability of DNA, two genera of bacterial pathogens are known to produce endospores, the aerobic Bacillus and anaerobic Clostridium. The high concentration of DPA in and specificity to bacterial endospores has long made it a target in analytical methods for the detection. Extensive subsequent work by scientists has elaborated on and further developed this approach. It is also used to prepare dipicolinato ligated lanthanide and transition metal complexes for ion chromatography, simple substituted pyridines vary significantly in environmental fate characteristics, such as volatility, adsorption, and biodegradation. Dipicolinic acid is among the least volatile, least adsorbed by soil, a number of studies have confirmed dipicolinic acid is biodegradable in aerobic and anaerobic environments, which is consistent with the widespread occurrence of the compound in nature. With a high solubility and limited sorption, utilization of acid as a growth substrate by microorganisms is not limited by bioavailability in nature. JPL Develops High-Speed Test to Improve Pathogen Decontamination at JPL
28.
Biological agent
–
In addition to these living and/or replicating pathogens, biological toxins are also included among the bio-agents. More than 1,200 different kinds of potentially weaponizable bio-agents have been described and studied to date, Biological agents have the ability to adversely affect human health in a variety of ways, ranging from relatively mild allergic reactions to serious medical conditions, including death. Many of these organisms are ubiquitous in the environment where they are found in water, soil, plants. Bio-agents may be amenable to weaponization to render them easier to deploy or disseminate, genetic modification may enhance their incapacitating or lethal properties, or render them imprevious to conventional treatments or preventives. Since many bio-agents reproduce rapidly and require minimal resources for propagation, the Biological Weapons Convention is an international treaty banning the use or stockpiling of bio-agents, as of February 2015 there were 171 state signatories. Bio-agents are, however, widely studied for defensive purposes under various biosafety levels, in 2008, according to a U. S. The former US biological warfare program categorized its weaponized anti-personnel bio-agents as either Lethal Agents or Incapacitating Agents, since 1997, United States law has declared a list of bio-agents designated by the U. S. Department of Health and Human Services or the U. S. Select agents are divided into HHS select agents and toxins, USDA select agents and toxins and Overlap select agents, centers for Disease Control and Prevention breaks biological agents into three categories, Category A, Category B, and Category C. Category A agents pose the greatest threat to the U. S, Category A agents include anthrax, botulism, plague, smallpox, tularemia, and viral hemorrhagic fevers. The following pathogens and toxins were weaponized by one nation or another at some time, NATO abbreviations are included where applicable. Additionally, the Soviet Union is known to have weaponized Marburg virus in the 1970s and 80s, simulants are organisms or substances which mimic physical or biological properties of real biological agents, without being pathogenic. They are used to study the efficiency of various dissemination techniques or the risks caused by the use of agents in bioterrorism. The typical size of simulants enables it to buildings with closed windows and doors. This bears a sigificant health risk, even if the agent is normally not pathogenic
29.
United Kingdom
–
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom or Britain, is a sovereign country in western Europe. Lying off the north-western coast of the European mainland, the United Kingdom includes the island of Great Britain, Northern Ireland is the only part of the United Kingdom that shares a land border with another sovereign state—the Republic of Ireland. The Irish Sea lies between Great Britain and Ireland, with an area of 242,500 square kilometres, the United Kingdom is the 78th-largest sovereign state in the world and the 11th-largest in Europe. It is also the 21st-most populous country, with an estimated 65.1 million inhabitants, together, this makes it the fourth-most densely populated country in the European Union. The United Kingdom is a monarchy with a parliamentary system of governance. The monarch is Queen Elizabeth II, who has reigned since 6 February 1952, other major urban areas in the United Kingdom include the regions of Birmingham, Leeds, Glasgow, Liverpool and Manchester. The United Kingdom consists of four countries—England, Scotland, Wales, the last three have devolved administrations, each with varying powers, based in their capitals, Edinburgh, Cardiff and Belfast, respectively. The relationships among the countries of the UK have changed over time, Wales was annexed by the Kingdom of England under the Laws in Wales Acts 1535 and 1542. A treaty between England and Scotland resulted in 1707 in a unified Kingdom of Great Britain, which merged in 1801 with the Kingdom of Ireland to form the United Kingdom of Great Britain and Ireland. Five-sixths of Ireland seceded from the UK in 1922, leaving the present formulation of the United Kingdom of Great Britain, there are fourteen British Overseas Territories. These are the remnants of the British Empire which, at its height in the 1920s, British influence can be observed in the language, culture and legal systems of many of its former colonies. The United Kingdom is a country and has the worlds fifth-largest economy by nominal GDP. The UK is considered to have an economy and is categorised as very high in the Human Development Index. It was the worlds first industrialised country and the worlds foremost power during the 19th, the UK remains a great power with considerable economic, cultural, military, scientific and political influence internationally. It is a nuclear weapons state and its military expenditure ranks fourth or fifth in the world. The UK has been a permanent member of the United Nations Security Council since its first session in 1946 and it has been a leading member state of the EU and its predecessor, the European Economic Community, since 1973. However, on 23 June 2016, a referendum on the UKs membership of the EU resulted in a decision to leave. The Acts of Union 1800 united the Kingdom of Great Britain, Scotland, Wales and Northern Ireland have devolved self-government
30.
Empire of Japan
–
The Empire of Japan was the historical Japanese nation-state and great power that existed from the Meiji Restoration in 1868 to the enactment of the 1947 constitution of modern Japan. Imperial Japans rapid industrialization and militarization under the slogan Fukoku Kyōhei led to its emergence as a world power, after several large-scale military successes during the Second Sino-Japanese War and the Pacific War, the Empire also gained notoriety for its war crimes against the peoples it conquered. A period of occupation by the Allies followed the surrender, Occupation and reconstruction continued well into the 1950s, eventually forming the current nation-state whose full title is the State of Japan or simply rendered Japan in English. The historical state is referred to as the Empire of Japan or the Japanese Empire or Imperial Japan in English. In Japanese it is referred to as Dai Nippon Teikoku, which translates to Greater Japanese Empire and this is analogous to Großdeutsches Reich, a term that translates to Greater German Empire in English and Dai Doitsu Teikoku in Japanese. This meaning is significant in terms of geography, encompassing Japan, due to its name in kanji characters and its flag, it was also given the exonym Empire of the Sun. After two centuries, the policy, or Sakoku, under the shoguns of the Edo period came to an end when the country was forced open to trade by the Convention of Kanagawa in 1854. The following years saw increased trade and interaction, commercial treaties between the Tokugawa shogunate and Western countries were signed. In large part due to the terms of these Unequal Treaties, the Shogunate soon faced internal hostility, which materialized into a radical, xenophobic movement. In March 1863, the Emperor issued the order to expel barbarians, although the Shogunate had no intention of enforcing the order, it nevertheless inspired attacks against the Shogunate itself and against foreigners in Japan. The Namamugi Incident during 1862 led to the murder of an Englishman, Charles Lennox Richardson, the British demanded reparations but were denied. While attempting to exact payment, the Royal Navy was fired on from coastal batteries near the town of Kagoshima and they responded by bombarding the port of Kagoshima in 1863. For Richardsons death, the Tokugawa government agreed to pay an indemnity, shelling of foreign shipping in Shimonoseki and attacks against foreign property led to the Bombardment of Shimonoseki by a multinational force in 1864. The Chōshū clan also launched the coup known as the Kinmon incident. The Satsuma-Chōshū alliance was established in 1866 to combine their efforts to overthrow the Tokugawa bakufu, in early 1867, Emperor Kōmei died of smallpox and was replaced by his son, Crown Prince Mutsuhito. On November 9,1867, Tokugawa Yoshinobu resigned from his post and authorities to the Emperor, however, while Yoshinobus resignation had created a nominal void at the highest level of government, his apparatus of state continued to exist. On January 3,1868, Satsuma-Chōshū forces seized the palace in Kyoto. On January 17,1868, Yoshinobu declared that he would not be bound by the proclamation of the Restoration, on January 24, Yoshinobu decided to prepare an attack on Kyoto, occupied by Satsuma and Chōshū forces
31.
United States
–
Forty-eight of the fifty states and the federal district are contiguous and located in North America between Canada and Mexico. The state of Alaska is in the northwest corner of North America, bordered by Canada to the east, the state of Hawaii is an archipelago in the mid-Pacific Ocean. The U. S. territories are scattered about the Pacific Ocean, the geography, climate and wildlife of the country are extremely diverse. At 3.8 million square miles and with over 324 million people, the United States is the worlds third- or fourth-largest country by area, third-largest by land area. It is one of the worlds most ethnically diverse and multicultural nations, paleo-Indians migrated from Asia to the North American mainland at least 15,000 years ago. European colonization began in the 16th century, the United States emerged from 13 British colonies along the East Coast. Numerous disputes between Great Britain and the following the Seven Years War led to the American Revolution. On July 4,1776, during the course of the American Revolutionary War, the war ended in 1783 with recognition of the independence of the United States by Great Britain, representing the first successful war of independence against a European power. The current constitution was adopted in 1788, after the Articles of Confederation, the first ten amendments, collectively named the Bill of Rights, were ratified in 1791 and designed to guarantee many fundamental civil liberties. During the second half of the 19th century, the American Civil War led to the end of slavery in the country. By the end of century, the United States extended into the Pacific Ocean. The Spanish–American War and World War I confirmed the status as a global military power. The end of the Cold War and the dissolution of the Soviet Union in 1991 left the United States as the sole superpower. The U. S. is a member of the United Nations, World Bank, International Monetary Fund, Organization of American States. The United States is a developed country, with the worlds largest economy by nominal GDP. It ranks highly in several measures of performance, including average wage, human development, per capita GDP. While the U. S. economy is considered post-industrial, characterized by the dominance of services and knowledge economy, the United States is a prominent political and cultural force internationally, and a leader in scientific research and technological innovations. In 1507, the German cartographer Martin Waldseemüller produced a map on which he named the lands of the Western Hemisphere America after the Italian explorer and cartographer Amerigo Vespucci
32.
Russia
–
Russia, also officially the Russian Federation, is a country in Eurasia. The European western part of the country is more populated and urbanised than the eastern. Russias capital Moscow is one of the largest cities in the world, other urban centers include Saint Petersburg, Novosibirsk, Yekaterinburg, Nizhny Novgorod. Extending across the entirety of Northern Asia and much of Eastern Europe, Russia spans eleven time zones and incorporates a range of environments. It shares maritime borders with Japan by the Sea of Okhotsk, the East Slavs emerged as a recognizable group in Europe between the 3rd and 8th centuries AD. Founded and ruled by a Varangian warrior elite and their descendants, in 988 it adopted Orthodox Christianity from the Byzantine Empire, beginning the synthesis of Byzantine and Slavic cultures that defined Russian culture for the next millennium. Rus ultimately disintegrated into a number of states, most of the Rus lands were overrun by the Mongol invasion. The Soviet Union played a role in the Allied victory in World War II. The Soviet era saw some of the most significant technological achievements of the 20th century, including the worlds first human-made satellite and the launching of the first humans in space. By the end of 1990, the Soviet Union had the second largest economy, largest standing military in the world. It is governed as a federal semi-presidential republic, the Russian economy ranks as the twelfth largest by nominal GDP and sixth largest by purchasing power parity in 2015. Russias extensive mineral and energy resources are the largest such reserves in the world, making it one of the producers of oil. The country is one of the five recognized nuclear weapons states and possesses the largest stockpile of weapons of mass destruction, Russia is a great power as well as a regional power and has been characterised as a potential superpower. The name Russia is derived from Rus, a state populated mostly by the East Slavs. However, this name became more prominent in the later history, and the country typically was called by its inhabitants Русская Земля. In order to distinguish this state from other states derived from it, it is denoted as Kievan Rus by modern historiography, an old Latin version of the name Rus was Ruthenia, mostly applied to the western and southern regions of Rus that were adjacent to Catholic Europe. The current name of the country, Россия, comes from the Byzantine Greek designation of the Kievan Rus, the standard way to refer to citizens of Russia is Russians in English and rossiyane in Russian. There are two Russian words which are translated into English as Russians
33.
Iraq
–
The capital, and largest city, is Baghdad. The main ethnic groups are Arabs and Kurds, others include Assyrians, Turkmen, Shabakis, Yazidis, Armenians, Mandeans, Circassians, around 95% of the countrys 36 million citizens are Muslims, with Christianity, Yarsan, Yezidism, and Mandeanism also present. The official languages of Iraq are Arabic and Kurdish, two major rivers, the Tigris and Euphrates, run south through Iraq and into the Shatt al-Arab near the Persian Gulf. These rivers provide Iraq with significant amounts of fertile land, the region between the Tigris and Euphrates rivers, historically known as Mesopotamia, is often referred to as the cradle of civilisation. It was here that mankind first began to read, write, create laws, the area has been home to successive civilisations since the 6th millennium BC. Iraq was the centre of the Akkadian, Sumerian, Assyrian and it was also part of the Median, Achaemenid, Hellenistic, Parthian, Sassanid, Roman, Rashidun, Umayyad, Abbasid, Ayyubid, Mongol, Safavid, Afsharid, and Ottoman empires. Iraqs modern borders were mostly demarcated in 1920 by the League of Nations when the Ottoman Empire was divided by the Treaty of Sèvres, Iraq was placed under the authority of the United Kingdom as the British Mandate of Mesopotamia. A monarchy was established in 1921 and the Kingdom of Iraq gained independence from Britain in 1932, in 1958, the monarchy was overthrown and the Iraqi Republic created. Iraq was controlled by the Arab Socialist Baath Party from 1968 until 2003, after an invasion by the United States and its allies in 2003, Saddam Husseins Baath Party was removed from power and multi-party parliamentary elections were held in 2005. The American presence in Iraq ended in 2011, but the Iraqi insurgency continued and intensified as fighters from the Syrian Civil War spilled into the country, the Arabic name العراق al-ʿIrāq has been in use since before the 6th century. There are several suggested origins for the name, one dates to the Sumerian city of Uruk and is thus ultimately of Sumerian origin, as Uruk was the Akkadian name for the Sumerian city of Urug, containing the Sumerian word for city, UR. An Arabic folk etymology for the name is rooted, well-watered. During the medieval period, there was a region called ʿIrāq ʿArabī for Lower Mesopotamia and ʿIrāq ʿajamī, for the region now situated in Central and Western Iran. The term historically included the south of the Hamrin Mountains. The term Sawad was also used in early Islamic times for the region of the plain of the Tigris and Euphrates rivers. In English, it is either /ɪˈrɑːk/ or /ɪˈræk/, the American Heritage Dictionary, the pronunciation /aɪˈræk/ is frequently heard in U. S. media. Since approximately 10,000 BC, Iraq was one of centres of a Caucasoid Neolithic culture where agriculture, the following Neolithic period is represented by rectangular houses. At the time of the pre-pottery Neolithic, people used vessels made of stone, gypsum, finds of obsidian tools from Anatolia are evidences of early trade relations
34.
Casimir Davaine
–
Casimir Davaine was a French physician known for his work in the field of microbiology. He was a native of Saint-Amand-les-Eaux, department of Nord, in 1850, Davaine along with French pathologist Pierre François Olive Rayer, discovered a certain microorganism in the blood of diseased and dying sheep. In the diseased blood, Rayer and Davaine observed the bacillus that is today as Bacillus anthracis. Soon afterwards, Rayer published a description of the bacillus in a paper titled, in 1863 Davaine demonstrated that the bacillus could be directly transmitted from one animal to another. He was able to identify the organism, but was unaware of its true etiology. Casimir Davaine is also credited for work in the study of septicemia. Nancy Tomes The Gospel of Germs, Men, Women, rocchietta, S. [Casimir Joseph Davaine, pioneer of medical microbiology. Théodoridès, J. Casimir Davaine, a precursor of Pasteur
35.
Robert Koch
–
Robert Heinrich Hermann Koch was a celebrated German physician and pioneering microbiologist. In addition to his studies on these diseases, Koch created and improved laboratory technologies and techniques in the field of microbiology. As a result of his research on tuberculosis, Koch received the Nobel Prize in Physiology or Medicine in 1905. Robert Koch was born in Clausthal, Hanover, Germany, on 11 December 1843, to Hermann Koch, Koch excelled in academics from an early age. Before entering school in 1848, he had taught himself how to read and he graduated from high school in 1862, having excelled in science and maths. At the age of 19, Koch entered the University of Göttingen, however, after three semesters, Koch decided to change his area of study to medicine, as he aspired to be a physician. During his fifth semester of school, Jacob Henle, an anatomist who had published a theory of contagion in 1840. In his sixth semester, Koch began to research at the Physiological Institute. This would eventually form the basis of his dissertation, in January 1866, Koch graduated from medical school, earning honors of the highest distinction. Several years after his graduation in 1866, he worked as a surgeon in the Franco-Prussian War, from 1880-1885, Koch held a position as government advisor with the Imperial Department of Health. Koch began conducting research on microorganisms in a laboratory connected to his patient examination room, koch’s early research in this laboratory yielded one of his major contributions to the field of microbiology, as he developed the technique of growing bacteria. Furthermore, he managed to isolate and grow selected pathogens in pure laboratory culture, from 1885 to 1890, he served as an administrator and professor at Berlin University. For this he accepted harsh conditions, the Prussian Ministry of Health insisted after the scandal with tuberculin, that any of Kochs inventions would unconditionally belong to the government and not compensated. Koch lost the right to apply for patent protection, in an attempt to grow bacteria, Koch began to use solid nutrients such as potato slices. Through these initial experiments, Koch observed individual colonies of identical and he found that potato slices were not suitable media for all organisms, and later began to use nutrient solutions with gelatin. Koch’s discovery of the agent of anthrax led to the formation of a generic set of postulates which can be used in the determination of the cause of most infectious diseases. The organism must be isolated from a host containing the disease, samples of the organism taken from pure culture must cause the same disease when inoculated into a healthy, susceptible animal in the laboratory. The organism must be isolated from the animal and must be identified as the same original organism first isolated from the originally diseased host
36.
Greek language
–
Greek is an independent branch of the Indo-European family of languages, native to Greece and other parts of the Eastern Mediterranean. It has the longest documented history of any living language, spanning 34 centuries of written records and its writing system has been the Greek alphabet for the major part of its history, other systems, such as Linear B and the Cypriot syllabary, were used previously. The alphabet arose from the Phoenician script and was in turn the basis of the Latin, Cyrillic, Armenian, Coptic, Gothic and many other writing systems. Together with the Latin texts and traditions of the Roman world, during antiquity, Greek was a widely spoken lingua franca in the Mediterranean world and many places beyond. It would eventually become the official parlance of the Byzantine Empire, the language is spoken by at least 13.2 million people today in Greece, Cyprus, Italy, Albania, Turkey, and the Greek diaspora. Greek roots are used to coin new words for other languages, Greek. Greek has been spoken in the Balkan peninsula since around the 3rd millennium BC, the earliest written evidence is a Linear B clay tablet found in Messenia that dates to between 1450 and 1350 BC, making Greek the worlds oldest recorded living language. Among the Indo-European languages, its date of earliest written attestation is matched only by the now extinct Anatolian languages, the Greek language is conventionally divided into the following periods, Proto-Greek, the unrecorded but assumed last ancestor of all known varieties of Greek. The unity of Proto-Greek would have ended as Hellenic migrants entered the Greek peninsula sometime in the Neolithic era or the Bronze Age, Mycenaean Greek, the language of the Mycenaean civilisation. It is recorded in the Linear B script on tablets dating from the 15th century BC onwards, Ancient Greek, in its various dialects, the language of the Archaic and Classical periods of the ancient Greek civilisation. It was widely known throughout the Roman Empire, after the Roman conquest of Greece, an unofficial bilingualism of Greek and Latin was established in the city of Rome and Koine Greek became a first or second language in the Roman Empire. The origin of Christianity can also be traced through Koine Greek, Medieval Greek, also known as Byzantine Greek, the continuation of Koine Greek in Byzantine Greece, up to the demise of the Byzantine Empire in the 15th century. Much of the written Greek that was used as the language of the Byzantine Empire was an eclectic middle-ground variety based on the tradition of written Koine. Modern Greek, Stemming from Medieval Greek, Modern Greek usages can be traced in the Byzantine period and it is the language used by the modern Greeks, and, apart from Standard Modern Greek, there are several dialects of it. In the modern era, the Greek language entered a state of diglossia, the historical unity and continuing identity between the various stages of the Greek language is often emphasised. Greek speakers today still tend to regard literary works of ancient Greek as part of their own rather than a foreign language and it is also often stated that the historical changes have been relatively slight compared with some other languages. According to one estimation, Homeric Greek is probably closer to demotic than 12-century Middle English is to modern spoken English, Greek is spoken by about 13 million people, mainly in Greece, Albania and Cyprus, but also worldwide by the large Greek diaspora. Greek is the language of Greece, where it is spoken by almost the entire population
37.
Skin
–
Skin is the soft outer tissue covering vertebrates. Other animal coverings, such as the arthropod exoskeleton have different developmental origin, structure, the adjective cutaneous means of the skin. In mammals, the skin is an organ of the system made up of multiple layers of ectodermal tissue. Skin of a different nature exists in amphibians, reptiles, all mammals have some hair on their skin, even marine mammals like whales, dolphins, and porpoises which appear to be hairless. The skin interfaces with the environment and is the first line of defense from external factors, for example, the skin plays a key role in protecting the body against pathogens and excessive water loss. Its other functions are insulation, temperature regulation, sensation, severely damaged skin may heal by forming scar tissue. This is sometimes discoloured and depigmented, the thickness of skin also varies from location to location on an organism. The skin on the palms and the soles of the feet is 4 mm thick, the speed and quality of wound healing in skin is promoted by the reception of estrogen. Primarily, fur augments the insulation the skin provides but can serve as a secondary sexual characteristic or as camouflage. On some animals, the skin is hard and thick. Reptiles and fish have hard scales on their skin for protection. Amphibian skin is not a barrier, especially regarding the passage of chemicals via skin and is often subject to osmosis. For example, a sitting in an anesthetic solution would be sedated quickly. Amphibian skin plays key roles in everyday survival and their ability to exploit a range of habitats. Keratinocytes are the cells, constituting 95% of the epidermis, while Merkel cells, melanocytes. Keratinocytes from the stratum corneum are eventually shed from the surface, the epidermis contains no blood vessels, and cells in the deepest layers are nourished by diffusion from blood capillaries extending to the upper layers of the dermis. The epidermis and dermis are separated by a sheet of fibers called the basement membrane. The dermis is the layer of skin beneath the epidermis consists of connective tissue and cushions the body from stress
38.
Gene
–
A gene is a locus of DNA which is made up of nucleotides and is the molecular unit of heredity. The transmission of genes to an offspring is the basis of the inheritance of phenotypic traits. These genes make up different DNA sequences called genotypes, genotypes along with environmental and developmental factors determine what the phenotypes will be. Most biological traits are under the influence of polygenes as well as gene–environment interactions, genes can acquire mutations in their sequence, leading to different variants, known as alleles, in the population. These alleles encode slightly different versions of a protein, which cause different phenotypical traits, usage of the term having a gene typically refers to containing a different allele of the same, shared gene. Genes evolve due to natural selection or survival of the fittest of the alleles, the concept of a gene continues to be refined as new phenomena are discovered. For example, regulatory regions of a gene can be far removed from its coding regions, some viruses store their genome in RNA instead of DNA and some gene products are functional non-coding RNAs. The existence of discrete inheritable units was first suggested by Gregor Mendel, from 1857 to 1864, in Brno, he studied inheritance patterns in 8000 common edible pea plants, tracking distinct traits from parent to offspring. He described these mathematically as 2n combinations where n is the number of differing characteristics in the original peas, although he did not use the term gene, he explained his results in terms of discrete inherited units that give rise to observable physical characteristics. This description prefigured the distinction between genotype and phenotype, charles Darwin developed a theory of inheritance he termed pangenesis, from Greek pan and genesis / genos. Darwin used the term gemmule to describe hypothetical particles that would mix during reproduction, de Vries called these units pangenes, after Darwins 1868 pangenesis theory. In 1909 the Danish botanist Wilhelm Johannsen shortened the name to gene, advances in understanding genes and inheritance continued throughout the 20th century. Deoxyribonucleic acid was shown to be the repository of genetic information by experiments in the 1940s to 1950s. In the early 1950s the prevailing view was that the genes in a chromosome acted like discrete entities, indivisible by recombination, collectively, this body of research established the central dogma of molecular biology, which states that proteins are translated from RNA, which is transcribed from DNA. This dogma has since shown to have exceptions, such as reverse transcription in retroviruses. The modern study of genetics at the level of DNA is known as molecular genetics, in 1972, Walter Fiers and his team at the University of Ghent were the first to determine the sequence of a gene, the gene for Bacteriophage MS2 coat protein. The subsequent development of chain-termination DNA sequencing in 1977 by Frederick Sanger improved the efficiency of sequencing, an automated version of the Sanger method was used in early phases of the Human Genome Project. The theories developed in the 1930s and 1940s to integrate molecular genetics with Darwinian evolution are called the evolutionary synthesis
39.
Ribosomal RNA
–
Ribosomal ribonucleic acid is the RNA component of the ribosome, and is essential for protein synthesis in all living organisms. It constitutes the predominant material within the ribosome, which is approximately 60% rRNA and 40% protein by weight, ribosomes contain two major rRNAs and 50 or more proteins. The ribosomal RNAs form two subunits, the large subunit and small subunit, the LSU rRNA acts as a ribozyme, catalyzing peptide bond formation. RRNA sequences are used for working out evolutionary relationships among organisms. The ribosomal RNAs complex with proteins to form two subunits, the large subunit and small subunit. During translation, mRNA is sandwiched between the small and large subunits, and the ribosome catalyzes the formation of a bond between the two amino acids that are contained in the rRNA. A ribosome also has three binding sites called A, P, and E, the A site in the ribosome binds to an aminoacyl-tRNA. This reaction is catalyzed by peptidyl transferase, the tRNA that was holding onto the last amino acid is moved to the E site, and what used to be the aminoacyl-tRNA is the peptidyl-tRNA. A single mRNA can be translated simultaneously by multiple ribosomes, the sedimentation rate of each subunit is affected by its shape, as well as by its mass. Thent units can be added as these represent the number of units in the linear rRNA polymers. In prokaryotes a small 30S ribosomal subunit contains the 16S ribosomal RNA, the large 50S ribosomal subunit contains two rRNA species. Bacterial 16S ribosomal RNA, 23S ribosomal RNA, and 5S rRNA genes are organized as a co-transcribed operon. There may be one or more copies of the operon dispersed in the genome, archaea contains either a single rDNA operon or multiple copies of the operon. The 3 end of the 16S ribosomal RNA binds to a sequence on the 5 end of mRNA called the Shine-Dalgarno sequence, in contrast, eukaryotes generally have many copies of the rRNA genes organized in tandem repeats, in humans approximately 300–400 repeats are present in five clusters. Because of their structure and transcription behaviour, rRNA gene clusters are commonly called ribosomal DNA. The 18S rRNA in most eukaryotes is in the small subunit. Mammalian cells have 2 mitochondrial rRNA molecules and 4 types of cytoplasmic rRNA, the 28S,5. 8S, and 18S rRNAs are encoded by a single transcription unit separated by 2 internally transcribed spacers. The 45S rDNA is organized into 5 clusters on chromosomes 13,14,15,21 and these are transcribed by RNA polymerase I
40.
Transfer RNA
–
A transfer RNA is an adaptor molecule composed of RNA, typically 76 to 90 nucleotides in length, that serves as the physical link between the mRNA and the amino acid sequence of proteins. It does this by carrying an amino acid to the protein synthetic machinery of a cell as directed by a sequence in a messenger RNA. As such, tRNAs are a component of translation, the biological synthesis of new proteins in accordance with the genetic code. The mRNA encodes a protein as a series of contiguous codons, one end of the tRNA matches the genetic code in a three-nucleotide sequence called the anticodon. The anticodon forms three base pairs with a codon in mRNA during protein biosynthesis, on the other end of the tRNA is a covalent attachment to the amino acid that corresponds to the anticodon sequence. Each type of molecule can be attached to only one type of amino acid. Because the genetic code contains multiple codons that specify the amino acid. The covalent attachment to the tRNA 3’ end is catalyzed by enzymes called aminoacyl tRNA synthetases, a large number of the individual nucleotides in a tRNA molecule may be chemically modified, often by methylation or deamidation. These unusual bases sometimes affect the interaction with ribosomes and sometimes occur in the anticodon to alter base-pairing properties. The structure of tRNA can be decomposed into its structure, its secondary structure. The cloverleaf structure becomes the 3D L-shaped structure through coaxial stacking of the helices, the lengths of each arm, as well as the loop diameter, in a tRNA molecule vary from species to species. The tRNA structure consists of the following, A 5-terminal phosphate group, the acceptor stem is a 7- to 9-base pair stem made by the base pairing of the 5-terminal nucleotide with the 3-terminal nucleotide. The acceptor stem may contain non-Watson-Crick base pairs, the CCA tail is a cytosine-cytosine-adenine sequence at the 3 end of the tRNA molecule. The amino acid loaded onto the tRNA by aminoacyl tRNA synthetases and this sequence is important for the recognition of tRNA by enzymes and critical in translation. In prokaryotes, the CCA sequence is transcribed in some tRNA sequences, in most prokaryotic tRNAs and eukaryotic tRNAs, the CCA sequence is added during processing and therefore does not appear in the tRNA gene. The D arm is a 4- to 6-bp stem ending in a loop that often contains dihydrouridine, the anticodon arm is a 5-bp stem whose loop contains the anticodon. The tRNA 5-to-3 primary structure contains the anticodon but in reverse order, the T arm is a 4- to 5- bp stem containing the sequence TΨC where Ψ is pseudouridine, a modified uridine. Bases that have modified, especially by methylation, occur in several positions throughout the tRNA
. PMID 12610093.
