Bacteria are a type of biological cell. They constitute a large domain of prokaryotic microorganisms. A few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, are present in most of its habitats. Bacteria inhabit soil, acidic hot springs, radioactive waste, the deep portions of Earth's crust. Bacteria live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, only about half of the bacterial phyla have species that can be grown in the laboratory; the study of bacteria is known as a branch of microbiology. There are 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water. There are 5×1030 bacteria on Earth, forming a biomass which exceeds that of all plants and animals. 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 dead bodies. In the biological communities surrounding hydrothermal vents and cold seeps, extremophile bacteria provide the nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane, to energy. Data reported by researchers in October 2012 and published in March 2013 suggested that bacteria thrive in the Mariana Trench, 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—they're adaptable to conditions, survive wherever they are."The famous notion that bacterial cells in the human body outnumber human cells by a factor of 10:1 has been debunked. There are 39 trillion bacterial cells in the human microbiota as personified by a "reference" 70 kg male 170 cm tall, whereas there are 30 trillion human cells in the body.
This means that although they do have the upper hand in actual numbers, it is only by 30%, not 900%. The largest number exist in the gut flora, a large number on the skin; the vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, though many are beneficial in the gut flora. However several species of bacteria are pathogenic and cause infectious diseases, including cholera, anthrax and bubonic plague; the most common fatal bacterial diseases are respiratory infections, with tuberculosis alone killing about 2 million people per year in sub-Saharan Africa. In developed countries, antibiotics are used to treat bacterial infections and are used in farming, making antibiotic resistance a growing problem. In industry, bacteria are important in sewage treatment and the breakdown of oil spills, the production of cheese and yogurt through fermentation, the recovery of gold, palladium and other metals in the mining sector, as well as in biotechnology, the manufacture of antibiotics and other chemicals.
Once regarded as plants 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 harbour membrane-bound organelles. Although the term bacteria traditionally included all prokaryotes, the scientific classification changed after the discovery in the 1990s that prokaryotes consist of two different groups of organisms that evolved from an ancient common ancestor; these evolutionary domains are called Archaea. The word bacteria is the plural of the New Latin bacterium, the latinisation of the Greek βακτήριον, the diminutive of βακτηρία, meaning "staff, cane", because the first ones to be discovered were rod-shaped; the ancestors of modern bacteria were unicellular microorganisms that were the first forms of life to appear on Earth, about 4 billion years ago. For about 3 billion years, most organisms were microscopic, bacteria and archaea were the dominant forms of life. Although bacterial fossils exist, such as stromatolites, their lack of distinctive morphology prevents them from being used to examine the history of bacterial evolution, or to date the time of origin of a particular bacterial species.
However, gene sequences can be used to reconstruct the bacterial phylogeny, these studies indicate that bacteria diverged first from the archaeal/eukaryotic lineage. The most recent common ancestor of bacteria and archaea was a hyperthermophile that lived about 2.5 billion–3.2 billion years ago. Bacteria were involved in the second great evolutionary divergence, that of the archaea and eukaryotes. Here, eukaryotes resulted from the entering of ancient bacteria into endosymbiotic associations with the ancestors of eukaryotic cells, which were themselves related to the Archaea; this involved the engulfment by proto-eukaryotic cells of alphaproteobacterial symbionts to form either mitochondria or hydrogenosomes, which are still found in all known Eukarya. Some eukaryotes that contained mitochondria engulfed cyanobacteria-like organisms, leading to the formation of chloroplasts in algae and plants; this is known as primary endosymbiosis. Bacteria display a wide diversity of sizes, called morphologies.
Bacterial cells are about one-tenth the size of eukaryotic cells
Friedrich Traugott Kützing
Friedrich Traugott Kützing was a German pharmacist and phycologist. Despite his limited background in regard to higher education, Kützing made significant scientific contributions. In 1833, he demonstrated differences between diatoms and desmids, thus separating the two groups into families of their own. Independent of Charles Cagniard-Latour and Theodor Schwann, he was among the first to provide comprehensive answers in regard to yeast and the role it played in fermentation. In 1849, he published Species Algarum, a massive work that provided descriptions for 6000 species of algae, he is the taxonomic authority of Phlebothamnion. As a young man, he worked in several pharmacies in Germany serving as assistant for a few semesters at the chemical-pharmaceutical institute of Franz Wilhelm Schweigger-Seidel at Halle. In 1835, he spent several months on a botanical excursion to Italy and Dalmatia, afterwards returning to Germany as a secondary school teacher of natural sciences in Nordhausen, a position his held until his retirement in 1883.
In 1837 he was awarded with an honorary doctorate from the University of Giessen, in 1843 received the title of professor. Über den naturgeschichtlichen Unterricht in Realschulen. Schulprogramm der Realschule, Nordhausen 1837 - On natural history teaching in secondary schools. Microscopische Untersuchungen über die Hefe und Essigmutter, nebst mehreren andern dazu gehörigen vegetabilischen Gebilden, in: J. prakt. Chem. 11, S. 385-409. - Microscopical studies of yeast, etc. Phycologia generalis oder Anatomie, Physiologie und Systemkunde der Tange, Leipzig 1843. Die kieselschaligen Bacillarien oder Diatomeen, Nordhausen 1844. - The silica-shelled Diatomea. Phycologica germanica, d. i. Deutschlands Algen in bündigen Beschreibungen. Nebst einer Anleitung zum Untersuchen und Bestimmen dieser Gewächse für Anfänger, Nordhausen 1845. - Algae from Germany in concise descriptions, etc. Species Algarum, Leipzig 1849. Biography @ Allgemeine Deutsche Biographie in German Natural History Museum Historic collections
Cyanobacteria known as Cyanophyta, are a phylum of bacteria that obtain their energy through photosynthesis and are the only photosynthetic prokaryotes able to produce oxygen. The name cyanobacteria comes from the color of the bacteria. Cyanobacteria, which are prokaryotes, are called "blue-green algae", though the term algae in modern usage is restricted to eukaryotes. Unlike heterotrophic prokaryotes, cyanobacteria have internal membranes; these are flattened. Phototrophic eukaryotes perform photosynthesis by plastids that may have their ancestry in cyanobacteria, acquired long ago via a process called endosymbiosis; these endosymbiotic cyanobacteria in eukaryotes may have evolved or differentiated into specialized organelles such as chloroplasts and leucoplasts. By producing and releasing oxygen, cyanobacteria are thought to have converted the early oxygen-poor, reducing atmosphere into an oxidizing one, causing the Great Oxygenation Event and the "rusting of the Earth", which changed the composition of the Earth's life forms and led to the near-extinction of anaerobic organisms.
Cyanobacteria are a group of photosynthetic bacteria, some of which are nitrogen-fixing, that live in a wide variety of moist soils and water either or in a symbiotic relationship with plants or lichen-forming fungi. They include colonial species. Colonies may form filaments, sheets, or hollow spheres; some filamentous species can differentiate into several different cell types: vegetative cells – the normal, photosynthetic cells that are formed under favorable growing conditions. Some cyanobacteria can fix atmospheric nitrogen in anaerobic conditions by means of specialized cells called heterocysts. Heterocysts may form under the appropriate environmental conditions when fixed nitrogen is scarce. Heterocyst-forming species are specialized for nitrogen fixation and are able to fix nitrogen gas into ammonia, nitrites or nitrates, which can be absorbed by plants and converted to protein and nucleic acids. Free-living cyanobacteria are present in the water of rice paddies, cyanobacteria can be found growing as epiphytes on the surfaces of the green alga, where they may fix nitrogen.
Cyanobacteria such as Anabaena can provide rice plantations with biofertilizer. Many cyanobacteria form motile filaments of cells, called hormogonia, that travel away from the main biomass to bud and form new colonies elsewhere; the cells in a hormogonium are thinner than in the vegetative state, the cells on either end of the motile chain may be tapered. To break away from the parent colony, a hormogonium must tear apart a weaker cell in a filament, called a necridium; each individual cell has a thick, gelatinous cell wall. They lack flagella. Many of the multicellular filamentous. In water columns, some cyanobacteria float by forming gas vesicles, as in archaea; these vesicles are not organelles as such. They are not bounded by a protein sheath. Cyanobacteria can be found in every terrestrial and aquatic habitat—oceans, fresh water, damp soil, temporarily moistened rocks in deserts, bare rock and soil, Antarctic rocks, they can form phototrophic biofilms. They are found in endolithic ecosystem. A few are endosymbionts in lichens, various protists, or sponges and provide energy for the host.
Some live in the fur of sloths. Aquatic cyanobacteria are known for their extensive and visible blooms that can form in both freshwater and marine environments; the blooms can have the appearance of blue-green scum. These blooms can be toxic, lead to the closure of recreational waters when spotted. Marine bacteriophages are significant parasites of unicellular marine cyanobacteria. Cyanobacteria growth is favored in ponds and lakes where waters are calm and have less turbulent mixing, their life cycles are disrupted when the water or artificially mixes from churning currents caused by the flowing water of streams or the churning water of fountains. For this reason blooms of cyanobacteria occur in rivers unless the water is flowing slowly. Growth is favored at higher temperatures, making increasing water temperature as a result of global warming more problematic. At higher temperatures Microcystis species are able to outcompete green algae; this is a concern because of the production of toxins produced by Microcystis.
Based on environmental trends and observations suggest cyanobacteria will increase their dominance in aquatic environments. This can lead to serious consequences the contamination of sources of drinking water. Cyanobacteria can interfere with water treatment in various ways by plugging filters and by producing cyanotoxins, which have the potential to cause serious illness if consumed. Consequences may lie within
Periphyton is a complex mixture of algae, heterotrophic microbes, detritus, attached to submerged surfaces in most aquatic ecosystems. The related term Aufwuchs refers to the collection of small animals and plants that adhere to open surfaces in aquatic environments, such as parts of rooted plants. Periphyton serves as an important food source for invertebrates and some fish, it can absorb contaminants, removing them from the water column and limiting their movement through the environment. The periphyton is an important indicator of water quality. Periphyton has been used as an experimental system in, e.g. pollution-induced community tolerance studies. In both marine and freshwater environments, algae – green algae and diatoms – make up the dominant component of aufwuchs communities. Small crustaceans and protozoans are commonly found in fresh water and the sea, but insect larvae and tardigrades are peculiar to freshwater aufwuchs faunas. Periphyton communities are used in aquaculture food production systems for the removal of solid and dissolved pollutants.
Their performance in filtration is established and their application as aquacultural feed is being researched. A risk for periphyton stems from urbanization. Increased turbidity levels associated with urban sprawl can smother periphyton causing its detachment from the rocks on which it lives, it can be important for the clearance of harmful chemicals and reducing turbidity. Periphyton serves as an indicator of water quality because: It has a high number of species, it has a fast response to changes. It is easy to sample, it is known for tolerance/sensitivity to change. Many aquatic animals feed extensively on aufwuchs; the mbuna cichlids from Lake Malawi are well known examples of fish adapted for feeding on aufwuchs. Examples include Labeotropheus Pseudotropheus zebra, they have scraper-like teeth. In marine communities, aufwuchs food sources are important for animals such as limpets and sea urchins. Biofilm Marine Biological Laboratory Sustainable Aquaculture Initiative Developing plant-based fish diets and pond management protocols for the Comprehensive Development Project in L’Acul, Haiti Macrophyte and Periphyton lab Fishbase definition of aufwuchs
The Nostocales are an order of cyanobacteria containing most of its species. It includes filamentous forms, both simple or branched, both those occurring as single strands or multiple strands within a sheath; some members show a decrease in width from the base, some have heterocysts. Environmentally, Nostocales is disregarded and not studied. However, a recent study suggests that the invasive cyanobacterium is occupying temperate lakes and thriving in them. Using principal component analysis and the Mann-Whitney U test, results showed that total phosphorus concentration was the primary causation for the increasing abundance of S.aphanizomenoides. Nostocales is known to grow in temperate environments consisting of poor light conditions and high phytoplankton biomass found in shallow lakes
The Nostocaceae are a family of cyanobacteria that forms filament-shaped colonies enclosed in mucus or a gelatinous sheath. Some genera in this family are found in fresh water, while others are found in salt water. Other genera may be found in both fresh and salt water. Like other cyanobacteria, these bacteria sometimes contain photosynthetic pigments in their cytoplasm to perform photosynthesis; the particular pigments they contain gives the cells a bluish-green color. Species of the Nostocaceae are known for their nitrogen-fixing abilities, they form symbiotic relationships with certain plants, such as the mosquito fern and hornworts; the cyanobacteria provide nitrogen to their hosts. Certain species of Anabaena have been used on rice paddy fields. Mosquito ferns carrying the cyanobacteria grow on the water in the fields during the growing season, they and the nitrogen they contain are plowed into the soil following the harvest, which has proved to be an effective natural fertilizer. The family Nostocaceae belongs to the order Nostocales.
Members of the family can be distinguished from those in other families by their unbranched filaments of cells arranged end-to-end, development of heterocysts among the cells of the filaments. Bold, Harold C. Alexopoulos, Constantine J. & Delevoryas, Theodore.. Morphology of Plants and Fungi. New York: Harper & Row. ISBN 0-06-040839-1. Drouet, Francis.. Revision of the Nostocaceae with Cylindrical Trichomes. New York: Hafner Press. ISBN 0-02-844060-9 Drouet, Francis.. Revision of the Stigonemataceae with a Summary of the Classification of the Blue-green Algae. Vaduz: J. Cramer. Nova Hedwigia: Heft 66. Microscopy U Great Lakes Waterlife Photo Gallery
Wikispecies is a wiki-based online project supported by the Wikimedia Foundation. Its aim is to create a comprehensive free content catalogue of all species. Jimmy Wales stated that editors are not required to fax in their degrees, but that submissions will have to pass muster with a technical audience. Wikispecies is available under the GNU Free Documentation License and CC BY-SA 3.0. Started in September 2004, with biologists across the world invited to contribute, the project had grown a framework encompassing the Linnaean taxonomy with links to Wikipedia articles on individual species by April 2005. Benedikt Mandl co-ordinated the efforts of several people who are interested in getting involved with the project and contacted potential supporters in early summer 2004. Databases were evaluated and the administrators contacted, some of them have agreed on providing their data for Wikispecies. Mandl defined two major tasks: Figure out how the contents of the data base would need to be presented—by asking experts, potential non-professional users and comparing that with existing databases Figure out how to do the software, which hardware is required and how to cover the costs—by asking experts, looking for fellow volunteers and potential sponsorsAdvantages and disadvantages were discussed by the wikimedia-I mailing list.
The board of directors of the Wikimedia Foundation voted by 4 to 0 in favor of the establishment of a Wikispecies. The project is hosted at species.wikimedia.org. It was merged to a sister project of Wikimedia Foundation on September 14, 2004. On October 10, 2006, the project exceeded 75,000 articles. On May 20, 2007, the project exceeded 100,000 articles with a total of 5,495 registered users. On September 8, 2008, the project exceeded 150,000 articles with a total of 9,224 registered users. On October 23, 2011, the project reached 300,000 articles. On June 16, 2014, the project reached 400,000 articles. On January 7, 2017, the project reached 500,000 articles. On October 30, 2018, the project reached 600,000 articles, a total of 1.12 million pages. Wikispecies comprises taxon pages, additionally pages about synonyms, taxon authorities, taxonomical publications, institutions or repositories holding type specimen. Wikispecies asks users to use images from Wikimedia Commons. Wikispecies does not allow the use of content.
All Species Foundation Catalogue of Life Encyclopedia of Life Tree of Life Web Project List of online encyclopedias The Plant List Wikispecies, The free species directory that anyone can edit Species Community Portal The Wikispecies Charter, written by Wales