Loricifera is a phylum of small to microscopic marine cycloneuralian sediment-dwelling animals with 37 described species, in nine genera. Aside from these described species, there are 100 more that have been collected and not yet described, their sizes range from 100 µm to ca. 1 mm. They are characterised by a protective outer case called a lorica and their habitat, in the spaces between marine gravel to which they attach themselves; the phylum was discovered in 1983 in Roscoff, France. They are among the most discovered groups of Metazoans, they attach themselves quite to the substrate, hence remained undiscovered for so long. The first specimen was collected in the 1970s, described in 1983, they are found at all depths, in different sediment types, in all latitudes. The animals have a head and digestive system as well as a lorica; the armor-like lorica consists of case of encircling plicae. There is no endocrine system. Many of the larvae are acoelomate, with some adults being pseudocoelomate, some remaining acoelomate.
Development is direct, though there are so-called Higgins larvae, which differ from adults in several respects. The animals have two sexes as adults. Complex and plastic life cycles of pliciloricids include paedogenetic stages with different forms of parthenogenetic reproduction. Fossils have been dated to the late Cambrian. Morphological studies have traditionally placed the phylum in the vinctiplicata with the Priapulida; the three phyla share four characters in common — chitinous cuticle, rings of scalids on the introvert and two rings of introvert retracts. However, mounting molecular evidence indicates a closer relationship with the Panarthropoda; the loriciferans are believed to be miniaturized descendants of a larger organism resembling the Cambrian fossil Sirilorica. However, the fossil record of the microscopic non-mineralized group is scarce, so it is difficult to trace out the phylum's evolutionary history in any detail; the 2017 discovery of Cambrian-era Eolorica deadwoodensis may shed some light on the group's history.
Three species of Loricifera have been found in the sediments at the bottom of the L'Atalante basin in Mediterranean Sea, more than 3,000 meters down, the first multicellular organisms known to spend their entire lives in an oxygen-free environment. They are able to do this because their mitochondria act like hydrogenosomes, allowing them to respire anaerobically; the newly reported animals complete their life cycle in the total absence of light and oxygen, they are less than a millimetre in size. They were collected from a deep basin at the bottom of the Mediterranean Sea, where they inhabit a nearly salt-saturated brine that, because of its density, does not mix with the waters above; as a consequence, this environment is anoxic and, due to the activity of sulfate reducers, contains sulphide at a concentration of 2.9 mM. Despite such harsh conditions, this anoxic and sulphidic environment is teeming with microbial life, both chemosynthetic prokaryotes that are primary producers, a broad diversity of eukaryotic heterotrophs at the next trophic level.
Nanaloricidae Kristensen, 1983 Pliciloricidae Higgins & Kristensen, 1986 Urnaloricidae Heiner & Møbjerg Kristensen, 2009 Extinct taxa Bernhard, Joan M.. "Metazoans of redoxcline sediments in Mediterranean deep-sea hypersaline anoxic basins". BMC Biology. 13: 105. Doi:10.1186/s12915-015-0213-6. PMC 4676161. PMID 26652623. Danovaro, Roberto. "The first metazoa living in permanently anoxic conditions". BMC Biology. 8: 30. Doi:10.1186/1741-7007-8-30. PMC 2907586. PMID 20370908. Fox-Skelly, Jasmin. "BBC Earth: There is one animal that seems to survive without oxygen". BBC News. Heiner, Iben. "Rugiloricus bacatus sp. nov. and a ghost‐larva with paedogenetic reproduction". Systematics and Biodiversity. 6: 225–47. Doi:10.1017/S147720000800265X. Ramel, Gordon. "The Brush Heads". "Can animals thrive without oxygen?". Woods Hole Oceanographic Institution. January 28, 2016. "Discovery of new fossil from half billion years ago sheds light on life on Earth". Science News. Retrieved 19 April 2017
Clostridium butyricum is a anaerobic endospore-forming Gram-positive butyric acid–producing bacillus subsisting by means of fermentation using an intracellularly accumulated amylopectin-like α-polyglucan as a substrate. It is uncommonly reported as a human pathogen and is used as a probiotic in Asia. C. butyricum is a soil inhabitant in various parts of the world, has been cultured from the stool of healthy children and adults, is common in soured milk and cheeses. The connection with dairy products is shown by the name: the butyr- in butyricum reflects the relevance of butyric acid in the bacteria's metabolism and the connection with Latin butyrum and Greek βούτυρον, with word roots pertaining to butter and cheese; the study of fermentation in the 19th century was of interest not only to basic science but as applied science funded by companies in certain industries, principally winemaking and brewing, as a means to reduce risk of bad batches through greater understanding and control of the process.
Thus early microbiologists such as Louis Pasteur were funded in their research into microbial metabolism and biochemistry. Such research led to the first understanding of anaerobic metabolism, butyric acid fermentation was humans' initial window into that world. In this connection it was circa 1880 when a scientist surnamed Prazmowski first assigned a name to Clostridium butyricum; the first C. butyricum MIYAIRI strain was isolated from the feces of Dr. Chikaji Miyairi in Japan in 1933, CBM 588 is the 588th MIYAIRI strain, isolated from a soil sample in Nagano, Japan, in 1963. Preparations based on CBM 588 have a long history of safe use in human populations in Asia Japan, where such products are variously classed as pharmaceutical drugs, "quasi drugs", OTC probiotics; the safe history of CBM 588 in human Asian populations is supported by various peer-reviewed publications and case studies dating back to 1963, including reports of CBM 588 use in severely-ill, immune-compromised and hospitalized patients, whose ages range from infants to elderly people, include pregnant women.
Its usefulness stems from its ability to interfere with the growth of pathogenic Clostridium difficile by antagonizing its multiplication. It is used in Japanese hospitals for C. difficile prophylaxis among in-patients and during administration of certain powerful antibiotics associated with opportunistic C. difficile infection. CBM 588 was approved for clinical use in humans by the Japanese Ministry of Health and Welfare in 1970; the standard preparation as marketed by Miyarisan Pharmaceutical consists of white, marked tablets each containing 0.35 × 106 colony forming units of C. butyricum MIYAIRI 588. CBM 588 does not establish permanently in the gut, in common with other orally administered probiotic bacteria. CBM 588 for clinical use is produced by submerged anaerobic fermentation followed by centrifugation, drying and packaging; the MIYAIRI 588 strain of C. butyricum does not carry any genes encoding any toxins and virulence factors associated with Clostridium or other enteropathogens. Absence of neurotoxin production has been demonstrated by polymerase chain reaction and Southern blot hybridisation for type E botulinum toxin gene.
The absence of genes encoding botulinum neurotoxin A,B,F and genes encoding non-toxic haemagglutinin and genes encoding Clostridium perfringens toxins has been demonstrated by PCR assay. This strain is deposited at the Fermentation Research Institute, Agency of Industrial Science and Technology, Japan under the strain name Clostridium butyricum MIYAIRI 588 strain, deposit number FERM BP-2789. Recent European Food Safety Authority opinions confirm the official strain nomenclature as Clostridium butyricum FERM BP-2789. Kyne, L. "Asymptomatic carriage of Clostridum difficile and serum levels of IgG antibody against toxin A". The New England Journal of Medicine. 342: 390–397. Doi:10.1056/nejm200002103420604. PMID 10666429. Leung, DY. "Treatment with intravenously administered gamma globulin of chronic relapsing colitis induced by Clostridium difficile toxin". Journal of Pediatrics. 118: 633–637. PMID 1901084. Clostridium butyricum at BacDive
The Polychaeta known as the bristle worms or polychaetes, are a paraphyletic class of annelid worms marine. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin; as such, polychaetes are sometimes referred to as bristle worms. More than 10,000 species are described in this class. Common representatives include the sandworm or clam worm Alitta. Polychaetes as a class are robust and widespread, with species that live in the coldest ocean temperatures of the abyssal plain, to forms which tolerate the high temperatures near hydrothermal vents. Polychaetes occur throughout the Earth's oceans at all depths, from forms that live as plankton near the surface, to a 2- to 3-cm specimen observed by the robot ocean probe Nereus at the bottom of the Challenger Deep, the deepest known spot in the Earth's oceans. Only 168 species are known from fresh waters. Polychaetes are segmented worms less than 10 cm in length, although ranging at the extremes from 1 mm to 3 m, in Eunice aphroditois.
They can sometimes be brightly coloured, may be iridescent or luminescent. Each segment bears a pair of paddle-like and vascularized parapodia, which are used for movement and, in many species, act as the worm's primary respiratory surfaces. Bundles of bristles, called setae, project from the parapodia. However, polychaetes vary from this generalised pattern, can display a range of different body forms; the most generalised polychaetes are those that crawl along the bottom, but others have adapted to many different ecological niches, including burrowing, pelagic life, tube-dwelling or boring and parasitism, requiring various modifications to their body structures. The head, or prostomium, is well developed, compared with other annelids, it projects forward over the mouth. The head includes two to four pair of eyes, although some species are blind; these are fairly simple structures, capable of distinguishing only light and dark, although some species have large eyes with lenses that may be capable of more sophisticated vision.
The head includes a pair of antennae, tentacle-like palps, a pair of pits lined with cilia, known as "nuchal organs". These latter appear to be chemoreceptors, help the worm to seek out food; the outer surface of the body wall consists of a simple columnar epithelium covered by a thin cuticle. Underneath this, in order, are a thin layer of connective tissue, a layer of circular muscle, a layer of longitudinal muscle, a peritoneum surrounding the body cavity. Additional oblique muscles move the parapodia. In most species the body cavity is divided into separate compartments by sheets of peritoneum between each segment, but in some species it's more continuous; the mouth of polychaetes is located on the peristomium, the segment behind the prostomium, varies in form depending on their diets, since the group includes predators, filter feeders and parasites. In general, they possess a pair of jaws and a pharynx that can be everted, allowing the worms to grab food and pull it into their mouths. In some species, the pharynx is modified into a lengthy proboscis.
The digestive tract is a simple tube with a stomach part way along. The smallest species, those adapted to burrowing, lack gills, breathing only through their body surfaces. Most other species have external gills associated with the parapodia. A simple but well-developed circulatory system is present; the two main blood vessels furnish smaller vessels to supply the gut. Blood flows forward in the dorsal vessel, above the gut, returns down the body in the ventral vessel, beneath the gut; the blood vessels themselves are contractile, helping to push the blood along, so most species have no need of a heart. In a few cases, muscular pumps analogous to a heart are found in various parts of the system. Conversely, some species have little or no circulatory system at all, transporting oxygen in the coelomic fluid that fills their body cavities; the blood may have any of three different respiratory pigments. The most common of these is haemoglobin, but some groups have haemerythrin or the green-coloured chlorocruorin, instead.
The nervous system consists of a single or double ventral nerve cord running the length of the body, with ganglia and a series of small nerves in each segment. The brain is large, compared with that of other annelids, lies in the upper part of the head. An endocrine gland is attached to the ventral posterior surface of the brain, appears to be involved in reproductive activity. In addition to the sensory organs on the head, photosensitive eye spots and numerous additional sensory nerve endings, most in involved with the sense of touch occur on the body. Polychaetes have a varying number of protonephridia or metanephridia for excreting waste, which in some cases can be complex in structure; the body contains greenish "chloragogen" tissue, similar to that found in oligochaetes, which appears to function in metabolism, in a similar fashion to that of the vertebrate liver. The cuticle may be 200 nm to 13 mm thick, their jaws are formed from sclerotised collagen, their setae from sclerotised chitin.
Polychaetes are variable in both form and lifestyle, include a few taxa that swim among the plankton or above the abyssal plain. Most burrow or build tubes in the sediment, some live as commensals. A few are pa
Archaea constitute a domain of single-celled microorganisms. These microbes are prokaryotes. Archaea were classified as bacteria, receiving the name archaebacteria, but this classification is outdated. Archaeal cells have unique properties separating them from the other two domains of life and Eukarya. Archaea are further divided into multiple recognized phyla. Classification is difficult because most have not been isolated in the laboratory and were only detected by analysis of their nucleic acids in samples from their environment. Archaea and bacteria are similar in size and shape, although a few archaea have shapes quite unlike that of bacteria, such as the flat and square-shaped cells of Haloquadratum walsbyi. Despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more related to those of eukaryotes, notably for the enzymes involved in transcription and translation. Other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes, including archaeols.
Archaea use more energy sources than eukaryotes: these range from organic compounds, such as sugars, to ammonia, metal ions or hydrogen gas. Salt-tolerant archaea use sunlight as an energy source, other species of archaea fix carbon, but unlike plants and cyanobacteria, no known species of archaea does both. Archaea reproduce asexually by budding; the first observed archaea were extremophiles, living in harsh environments, such as hot springs and salt lakes with no other organisms, but improved detection tools led to the discovery of archaea in every habitat, including soil and marshlands. They are part of the microbiota of all organisms, in the human microbiota they are important in the gut, on the skin. Archaea are numerous in the oceans, the archaea in plankton may be one of the most abundant groups of organisms on the planet. Archaea are a major part of Earth's life, may play roles in the carbon cycle and the nitrogen cycle. No clear examples of archaeal pathogens or parasites are known. Instead they are mutualists or commensals, such as the methanogens that inhabit the gastrointestinal tract in humans and ruminants, where their vast numbers aid digestion.
Methanogens are used in biogas production and sewage treatment, biotechnology exploits enzymes from extremophile archaea that can endure high temperatures and organic solvents. For much of the 20th century, prokaryotes were regarded as a single group of organisms and classified based on their biochemistry and metabolism. For example, microbiologists tried to classify microorganisms based on the structures of their cell walls, their shapes, the substances they consume. In 1965, Emile Zuckerkandl and Linus Pauling proposed instead using the sequences of the genes in different prokaryotes to work out how they are related to each other; this phylogenetic approach is the main method used today. Archaea – at that time only the methanogens were known – were first classified separately from bacteria in 1977 by Carl Woese and George E. Fox based on their ribosomal RNA genes, they called these groups the Urkingdoms of Archaebacteria and Eubacteria, though other researchers treated them as kingdoms or subkingdoms.
Woese and Fox gave the first evidence for Archaebacteria as a separate "line of descent": 1. Lack of peptidoglycan in their cell walls, 2. Two unusual coenzymes, 3. Results of 16S ribosomal RNA gene sequencing. To emphasize this difference, Otto Kandler and Mark Wheelis proposed reclassifying organisms into three natural domains known as the three-domain system: the Eukarya, the Bacteria and the Archaea, in what is now known as "The Woesian Revolution"; the word archaea comes from the Ancient Greek ἀρχαῖα, meaning "ancient things", as the first representatives of the domain Archaea were methanogens and it was assumed that their metabolism reflected Earth's primitive atmosphere and the organisms' antiquity, but as new habitats were studied, more organisms were discovered. Extreme halophilic and hyperthermophilic microbes were included in Archaea. For a long time, archaea were seen as extremophiles that only exist in extreme habitats such as hot springs and salt lakes, but by the end of the 20th century, archaea had been identified in non-extreme environments as well.
Today, they are known to be a large and diverse group of organisms abundantly distributed throughout nature. This new appreciation of the importance and ubiquity of archaea came from using polymerase chain reaction to detect prokaryotes from environmental samples by multiplying their ribosomal genes; this allows the detection and identification of organisms that have not been cultured in the laboratory. The classification of archaea, of prokaryotes in general, is a moving and contentious field. Current classification systems aim to organize archaea into groups of organisms that share structural features and common ancestors; these classifications rely on the use of the sequence of ribosomal RNA genes to reveal relationships between organisms. Most of the culturable and well-investigated species of archaea are members of two main phyla, the Euryarchaeota and Crenarchaeota. Other groups have been tentatively created. For example, the peculiar species Nanoarchaeum equitans, discovered in 2003, has been given its own phylum, the Nanoarchaeota.
A new phylum Korarchaeota has been proposed. It contains a sm
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group on the periodic table, a reactive nonmetal, an oxidizing agent that forms oxides with most elements as well as with other compounds. By mass, oxygen is the third-most abundant element in the universe, after helium. At standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless and odorless diatomic gas with the formula O2. Diatomic oxygen gas constitutes 20.8% of the Earth's atmosphere. As compounds including oxides, the element makes up half of the Earth's crust. Dioxygen is used in cellular respiration and many major classes of organic molecules in living organisms contain oxygen, such as proteins, nucleic acids and fats, as do the major constituent inorganic compounds of animal shells and bone. Most of the mass of living organisms is oxygen as a component of water, the major constituent of lifeforms. Oxygen is continuously replenished in Earth's atmosphere by photosynthesis, which uses the energy of sunlight to produce oxygen from water and carbon dioxide.
Oxygen is too chemically reactive to remain a free element in air without being continuously replenished by the photosynthetic action of living organisms. Another form of oxygen, ozone absorbs ultraviolet UVB radiation and the high-altitude ozone layer helps protect the biosphere from ultraviolet radiation. However, ozone present at the surface is a byproduct of thus a pollutant. Oxygen was isolated by Michael Sendivogius before 1604, but it is believed that the element was discovered independently by Carl Wilhelm Scheele, in Uppsala, in 1773 or earlier, Joseph Priestley in Wiltshire, in 1774. Priority is given for Priestley because his work was published first. Priestley, called oxygen "dephlogisticated air", did not recognize it as a chemical element; the name oxygen was coined in 1777 by Antoine Lavoisier, who first recognized oxygen as a chemical element and characterized the role it plays in combustion. Common uses of oxygen include production of steel and textiles, brazing and cutting of steels and other metals, rocket propellant, oxygen therapy, life support systems in aircraft, submarines and diving.
One of the first known experiments on the relationship between combustion and air was conducted by the 2nd century BCE Greek writer on mechanics, Philo of Byzantium. In his work Pneumatica, Philo observed that inverting a vessel over a burning candle and surrounding the vessel's neck with water resulted in some water rising into the neck. Philo incorrectly surmised that parts of the air in the vessel were converted into the classical element fire and thus were able to escape through pores in the glass. Many centuries Leonardo da Vinci built on Philo's work by observing that a portion of air is consumed during combustion and respiration. In the late 17th century, Robert Boyle proved. English chemist John Mayow refined this work by showing that fire requires only a part of air that he called spiritus nitroaereus. In one experiment, he found that placing either a mouse or a lit candle in a closed container over water caused the water to rise and replace one-fourteenth of the air's volume before extinguishing the subjects.
From this he surmised that nitroaereus is consumed in both combustion. Mayow observed that antimony increased in weight when heated, inferred that the nitroaereus must have combined with it, he thought that the lungs separate nitroaereus from air and pass it into the blood and that animal heat and muscle movement result from the reaction of nitroaereus with certain substances in the body. Accounts of these and other experiments and ideas were published in 1668 in his work Tractatus duo in the tract "De respiratione". Robert Hooke, Ole Borch, Mikhail Lomonosov, Pierre Bayen all produced oxygen in experiments in the 17th and the 18th century but none of them recognized it as a chemical element; this may have been in part due to the prevalence of the philosophy of combustion and corrosion called the phlogiston theory, the favored explanation of those processes. Established in 1667 by the German alchemist J. J. Becher, modified by the chemist Georg Ernst Stahl by 1731, phlogiston theory stated that all combustible materials were made of two parts.
One part, called phlogiston, was given off when the substance containing it was burned, while the dephlogisticated part was thought to be its true form, or calx. Combustible materials that leave little residue, such as wood or coal, were thought to be made of phlogiston. Air did not play a role in phlogiston theory, nor were any initial quantitative experiments conducted to test the idea. Polish alchemist and physician Michael Sendivogius in his work De Lapide Philosophorum Tractatus duodecim e naturae fonte et manuali experientia depromti described a substance contained in air, referring to it as'cibus vitae', this substance is identical with oxygen. Sendivogius, during his experiments performed between 1598 and 1604, properly recognized that the substance is equivalent to the gaseous byproduct released by the thermal decomposition of potassium nitrate. In Bugaj’s view, the isolation of oxygen and the proper association of the substance to that part of air, required for life, lends sufficient weight to the discovery of oxygen by Sendivogius.
Thioglycolate broth is a multipurpose, differential medium used to determine the oxygen requirements of microorganisms. Sodium thioglycolate in the medium permits the growth of obligate anaerobes. This, combined with the diffusion of oxygen from the top of the broth, produces a range of oxygen concentrations in the medium along its depth; the oxygen concentration at a given level is indicated by a redox-sensitive dye such as resazurine that turns pink in the presence of oxygen. This allows the differentiation of obligate aerobes, obligate anaerobes, facultative anaerobes and aerotolerant organisms. For example, obligately anaerobic Clostridium species will be seen growing only in the bottom of the test tube. Thioglycolate broth is used to recruit macrophages to the peritoneal cavity of mice when injected intraperitoneally, it recruits numerous macrophages, but does not activate them
A hypersaline lake is a landlocked body of water that contains significant concentrations of sodium chloride or other salts, with saline levels surpassing that of ocean water. Specific microbial and crustacean species thrive in these high-salinity environments that are inhospitable to most lifeforms; some of these species enter a dormant state when desiccated, some species are thought to survive for over 250 million years. The water of hypersaline lakes has great buoyancy due to its high salt content; the most saline water body in the world is the Don Juan Pond, located in the McMurdo Dry Valleys in Antarctica. Its volume is some 3,000 cubic meters, but is changing; the Don Juan Pond has a salinity level of over 44%. Its high salinity prevents the Don Juan from freezing when temperatures are below −50 °C. There are larger hypersaline water bodies, lakes in the McMurdo Dry Valleys such as Lake Vanda with salinity of over 35%, they are covered with ice in the winter. The most saline lake outside of Antarctica is Lake Assal, in Djibouti, which has a salinity of 34.8%.
The best-known hypersaline lakes are the Dead Sea and the Great Salt Lake in the state of Utah, USA. The Dead Sea, dividing Israel and the Palestinian West Bank from Jordan, is the world's deepest hypersaline lake, the Araruama Lagoon in Brazil is the world's largest; the Great Salt Lake, located in Utah, while having nearly three times the surface area of the Dead Sea, is shallower and experiences much greater fluctuations in salinity than the Dead Sea. At its lowest recorded levels, it approaches 7.7 times the salinity of ocean water, but when its levels are high, its salinity drops to only higher than the ocean. Hypersaline lakes are found on every continent in arid or semi-arid regions; the Devon Ice Cap contains two subglacial lakes. Brine pool – An area of high density brine collected in a depression on the ocean floor Halocline – Stratification of a body of water due to salinity differences Halophile List of bodies of water by salinity Salt lake