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Methanogens
Methanogens are microorganisms that produce methane as a metabolic byproduct in hypoxic conditions. They are prokaryotic and belong to the domain Archaea. All known methanogens are members of the archaeal phylum Euryarchaeota. Methanogens are common in wetlands, where they are responsible for marsh gas, and in the digestive tracts of animals such as ruminants and many humans, where they are responsible for the methane content of belching in ruminants and flatulence in humans. In marine sediments, the biological production of methane, also termed methanogenesis, is generally confined to where sulfates are depleted, below the top layers. Moreover, methanogenic archaea populations play an indispensable role in anaerobic wastewater treatments. Others are extremophiles, found in environments such as hot springs and submarine hydrothermal vents as well as in the "solid" rock of Earth's crust, kilometers below the surface. Physical description Methanogens are coccoid (spherical shaped ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archaea
Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebacteria kingdom), but this term has fallen out of use. Archaeal cells have unique properties separating them from the other two domains, Bacteria and Eukaryota. Archaea are further divided into multiple recognized phyla. Classification is difficult because most have not been isolated in a laboratory and have been detected only by their gene sequences in environmental samples. Archaea and bacteria are generally similar in size and shape, although a few archaea have very different shapes, such as the flat, square cells of '' Haloquadratum walsbyi''. Despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes invo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Earth makes it an economically attractive fuel, although capturing and storing it poses technical challenges due to its gaseous state under normal conditions for temperature and pressure. Naturally occurring methane is found both below ground and under the seafloor and is formed by both geological and biological processes. The largest reservoir of methane is under the seafloor in the form of methane clathrates. When methane reaches the surface and the atmosphere, it is known as atmospheric methane. The Earth's atmospheric methane concentration has increased by about 150% since 1750, and it accounts for 20% of the total radiative forcing from all of the long-lived and globally mixed greenhouse gases. It has also been detected ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methanogenesis
Methanogenesis or biomethanation is the formation of methane coupled to energy conservation by microbes known as methanogens. Organisms capable of producing methane for energy conservation have been identified only from the domain Archaea, a group phylogenetically distinct from both eukaryotes and bacteria, although many live in close association with anaerobic bacteria. Other forms of methane production that are not coupled to ATP synthesis exist within all three domains of life. The production of methane is an important and widespread form of microbial metabolism. In anoxic environments, it is the final step in the decomposition of biomass. Methanogenesis is responsible for significant amounts of natural gas accumulations, the remainder being thermogenic. Biochemistry Methanogenesis in microbes is a form of anaerobic respiration. Methanogens do not use oxygen to respire; in fact, oxygen inhibits the growth of methanogens. The terminal electron acceptor in methanogenesis is n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogenotroph
Hydrogenotrophs are organisms that are able to metabolize molecular hydrogen as a source of energy. An example of hydrogenotrophy is performed by carbon dioxide-reducing organismsStams, J.M., and Plugge, C.M. (2010) The microbiology of methanogenesis. ''In'' Reay, D., Smith, P., and Van Amstel, A., eds. ''Methane and Climate Change'', 14-26. which use CO2 and H2 to produce methane (CH4) by the following reaction: *CO2 + 4H2 → CH4 + 2H2O Other hydrogenotrophic metabolic pathways include acetogenesis, sulfate reduction, and other hydrogen oxidizing bacteria. Those that metabolize methane are called methanogenic. Hydrogenotrophs belong to a group of organisms known as methanogens, organisms that carry out anaerobic processes that are responsible for the production of methane through carbon dioxide reduction. Methanogens also include a group of organisms called methylotrophs, organisms that can use single-carbon molecules or molecules with no carbon-carbon bonds. Background ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marsh Gas
Marsh gas, also known as swamp gas or bog gas, is a mixture primarily of methane and smaller amounts of hydrogen sulfide, carbon dioxide, and trace phosphine that is produced naturally within some geographical marshes, swamps, and bogs. The surface of marshes, swamps, and bogs is initially porous vegetation that rots to form a crust that prevents oxygen from reaching the organic material trapped below. That is the condition that allows anaerobic digestion and fermentation of any plant or animal matter, which then produces methane. The trapped methane can escape through any of three main pathways: by the diffusion of methane molecules across an air–water interface, by bubbling out of water in a process known as ebullition, or through plant-mediated transport. Methane formation Methane is the primary gas that makes up the product colloquially known as "marsh gas". Much of the biogenic methane produced in nature is derived from either acetate cleavage or by the hydrogen reduct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flatulence
Flatulence, in humans, is the expulsion of gas from the intestines via the anus, commonly referred to as farting. "Flatus" is the medical word for gas generated in the stomach or bowels. A proportion of intestinal gas may be swallowed environmental air, and hence flatus is not entirely generated in the stomach or bowels. The scientific study of this area of medicine is termed flatology. Flatus is brought to the rectum and pressurized by muscles in the intestines. It is normal to pass flatus ("to fart"), though volume and frequency vary greatly among individuals. It is also normal for intestinal gas to have a feculent or unpleasant odor, which may be intense. The noise commonly associated with flatulence (" blowing a raspberry") is produced by the anus and buttocks, which act together in a manner similar to that of an embouchure. Both the sound and odor are sources of embarrassment, annoyance or amusement ( flatulence humor). There are several general symptoms related to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methanosarcina Barkeri
'' Methanosarcina barkeri'' is the most fundamental species of the genus '' Methanosarcina'', and their properties apply generally to the genus ''Methanosarcina''. ''Methanosarcina barkeri'' can produce methane anaerobically through different metabolic pathways. ''M. barkeri'' can subsume a variety of molecules for ATP production, including methanol, acetate, methylamines, and different forms of hydrogen and carbon dioxide. Although it is a slow developer and is sensitive to change in environmental conditions, ''M. barkeri'' is able to grow in a variety of different substrates, adding to its appeal for genetic analysis. Additionally, ''M. barkeri'' is the first organism in which the amino acid pyrrolysine was found. Furthermore, two strains of ''M. barkeri'', ''M. b. Fusaro'' and ''M. b. MS'' have been identified to possess an F-type ATPase (unusual for archaea, but common for bacteria, mitochondria and chloroplasts) along with an A-type ATPase. Location and structure The f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ruminant
Ruminants (suborder Ruminantia) are hoofed herbivorous grazing or browsing mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. The process, which takes place in the front part of the digestive system and therefore is called foregut fermentation, typically requires the fermented ingesta (known as cud) to be regurgitated and chewed again. The process of rechewing the cud to further break down plant matter and stimulate digestion is called rumination. The word "ruminant" comes from the Latin ''ruminare'', which means "to chew over again". The roughly 200 species of ruminants include both domestic and wild species. Ruminating mammals include cattle, all domesticated and wild bovines, goats, sheep, giraffes, deer, gazelles, and antelopes.Fowler, M.E. (2010).Medicine and Surgery of Camelids, Ames, Iowa: Wiley-Blackwell. Chapter 1 General Biology and Evolution addresses th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Euryarchaeota
Euryarchaeota (from Ancient Greek ''εὐρύς'' eurús, "broad, wide") is a phylum of archaea. Euryarchaeota are highly diverse and include methanogens, which produce methane and are often found in intestines, halobacteria, which survive extreme concentrations of salt, and some extremely thermophilic aerobes and anaerobes, which generally live at temperatures between 41 and 122 °C. They are separated from the other archaeans based mainly on rRNA sequences and their unique DNA polymerase. Description The ''Euryarchaeota'' are diverse in appearance and metabolic properties. The phylum contains organisms of a variety of shapes, including both rods and cocci. ''Euryarchaeota'' may appear either gram-positive or gram-negative depending on whether pseudomurein is present in the cell wall. ''Euryarchaeota'' also demonstrate diverse lifestyles, including methanogens, halophiles, sulfate-reducers, and extreme thermophiles in each. Others live in the ocean, suspended with plan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haloarchaea
Haloarchaea (halophilic archaea, halophilic archaebacteria, halobacteria) are a class of the Euryarchaeota, found in water saturated or nearly saturated with salt. Halobacteria are now recognized as archaea rather than bacteria and are one of the largest groups. The name 'halobacteria' was assigned to this group of organisms before the existence of the domain Archaea was realized, and while valid according to taxonomic rules, should be updated. Halophilic archaea are generally referred to as haloarchaea to distinguish them from halophilic bacteria. These microorganisms are among the halophile organisms, that they require high salt concentrations to grow, with most species requiring more than 2.0M NaCl for growth and survival. They are a distinct evolutionary branch of the Archaea distinguished by the possession of ether-linked lipids and the absence of murein in their cell walls. Haloarchaea can grow aerobically or anaerobically. Parts of the membranes of haloarchaea are pur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superoxide Dismutase
Superoxide dismutase (SOD, ) is an enzyme that alternately catalyzes the dismutation (or partitioning) of the superoxide () radical into ordinary molecular oxygen (O2) and hydrogen peroxide (). Superoxide is produced as a by-product of oxygen metabolism and, if not regulated, causes many types of cell damage. Hydrogen peroxide is also damaging and is degraded by other enzymes such as catalase. Thus, SOD is an important antioxidant defense in nearly all living cells exposed to oxygen. One exception is ''Lactobacillus plantarum'' and related lactobacilli, which use a different mechanism to prevent damage from reactive . Chemical reaction SODs catalyze the disproportionation of superoxide: : 2 HO2 → O2 + H2O2 In this way, is converted into two less damaging species. The pathway by which SOD-catalyzed dismutation of superoxide may be written, for Cu,Zn SOD, with the following reactions: * Cu2+-SOD + → Cu+-SOD + O2 (reduction of copper; oxidation of superoxide) * Cu+ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monophyletic
In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic groups are typically characterised by shared derived characteristics ( synapomorphies), which distinguish organisms in the clade from other organisms. An equivalent term is holophyly. The word "mono-phyly" means "one-tribe" in Greek. Monophyly is contrasted with paraphyly and polyphyly as shown in the second diagram. A ''paraphyletic group'' consists of all of the descendants of a common ancestor minus one or more monophyletic groups. A '' polyphyletic group'' is characterized by convergent features or habits of scientific interest (for example, night-active primates, fruit trees, aquatic insects). The features by which a polyphyletic group is differentiated from others are not inherited from a common ancestor. These definitions have ta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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