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Primary nutritional groups are groups of organisms, divided in relation to the nutrition mode according to the sources of energy and carbon, needed for living, growth and reproduction. The sources of energy can be light or chemical compounds; the sources of carbon can be of organic or inorganic origin.
Methanogens are microorganisms that produce methane as a metabolic byproduct in hypoxic conditions. They are prokaryotic and belong to the domain of archaea. They 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.
Methanogenesis or biomethanation is the formation of methane by microbes known as methanogens. Organisms capable of producing methane 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. 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.
Microbial ecology is the ecology of microorganisms: their relationship with one another and with their environment. It concerns the three major domains of life—Eukaryota, Archaea, and Bacteria—as well as viruses.
Methanotrophs are prokaryotes that metabolize methane as their source of carbon and energy. They can be either bacteria or archaea and can grow aerobically or anaerobically, and require single-carbon compounds to survive.
Sulfate-reducing microorganisms (SRM) or sulfate-reducing prokaryotes (SRP) are a group composed of sulfate-reducing bacteria (SRB) and sulfate-reducing archaea (SRA), both of which can perform anaerobic respiration utilizing sulfate (SO42–) as terminal electron acceptor, reducing it to hydrogen sulfide (H2S). Therefore, these sulfidogenic microorganisms "breathe" sulfate rather than molecular oxygen (O2), which is the terminal electron acceptor reduced to water (H2O) in aerobic respiration.
An acetogen is a microorganism that generates acetate (CH3COO−) as an end product of anaerobic respiration or fermentation. However, this term is usually employed in a narrower sense only to those bacteria and archaea that perform anaerobic respiration and carbon fixation simultaneously through the reductive acetyl coenzyme A (acetyl-CoA) pathway (also known as the Wood-Ljungdahl pathway). These genuine acetogens are also known as "homoacetogens" and they can produce acetyl-CoA (and from that, in most cases, acetate as the end product) from two molecules of carbon dioxide (CO2) and four molecules of molecular hydrogen (H2). This process is known as acetogenesis, and is different from acetate fermentation, although both occur in the absence of molecular oxygen (O2) and produce acetate. Although previously thought that only bacteria are acetogens, some archaea can be considered to be acetogens.
Microbial metabolism is the means by which a microbe obtains the energy and nutrients it needs to live and reproduce. Microbes use many different types of metabolic strategies and species can often be differentiated from each other based on metabolic characteristics. The specific metabolic properties of a microbe are the major factors in determining that microbe's ecological niche, and often allow for that microbe to be useful in industrial processes or responsible for biogeochemical cycles.
In biology, syntrophy, synthrophy, or cross-feeding is the phenomenon of one species living off the metabolic products of another species. In this type of biological interaction, the growth of one partner depends on the nutrients, growth factors, or substrates provided by the other partner. Jan Dolfing describes syntrophy as "the critical interdependency between producer and consumer". This term for nutritional interdependence is often used in microbiology to describe this symbiotic relationship between bacterial species. Morris et al. have described the process as "obligately mutualistic metabolism".
The Wood–Ljungdahl pathway is a set of biochemical reactions used by some bacteria and archaea called acetogens and methanogens, respectively. It is also known as the reductive acetyl-coenzyme A (Acetyl-CoA) pathway. This pathway enables these organisms to use hydrogen as an electron donor, and carbon dioxide as an electron acceptor and as a building block for biosynthesis.
Anaerobic oxidation of methane (AOM) is a microbial process occurring in anoxic marine and freshwater sediments. During AOM methane is oxidized with different terminal electron acceptors such as sulfate, nitrate, nitrite and metals.
Archaea constitute 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, but this term has fallen out of use.
Bacterial anoxygenic photosynthesis is differentiated from the more renowned terrestrial plant oxygenic photosynthesis by method of a terminal reductant that is and the byproduct which is hence, produced.
Ruminococcus is a genus of bacteria in the class Clostridia. They are anaerobic, Gram-positive gut microbes. One or more species in this genus are found in significant numbers in the human gut microbiota. The type species is R. flavefaciens. As usual, bacteria taxonomy is in flux, with Clostridia being paraphyletic, and some erroneous members of Ruminococcus being reassigned to a new genus Blautia on the basis of 16S rRNA gene sequences.
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 along with an A-type ATPase.
Hydrogenotrophs are organisms that are able to metabolize molecular hydrogen as a source of energy.
Dissimilatory sulfate reduction is a form of anaerobic respiration that uses sulfate as the terminal electron acceptor. This metabolism is found in some types of bacteria and archaea which are often termed sulfate-reducing organisms.
The genus Wolinella is a member of the Campylobacterales order of Bacteria. The order Campylobacterales includes human pathogens such as Helicobacter pylori and Campylobacter jejuni.
Methanogens are a group of microorganisms that can produce methane as a byproduct of their metabolism.They hold an important place in the digestive system of ruminants. The digestive tract of ruminants contain four major parts, they are abomasum, rumen, omasum and reticulum.The food with saliva is first passed to the rumen for breaking them into smaller particles and then it moves to the reticulum where the food is broken into further smaller particles and the indigestable particles are sent back for rechewing and then to rumen. The majority of the anaerobic microbes assisting the cellulose breakdown occupy the rumen. They initiate the fermentation process.The animal absorbs the fatty acids, vitamins and nutrient content on passing the partially digested food from rumen to omasum which, decreases the pH level and thus initiates the release of enzymes for further break down the food which is later passed to the abomasum that absorbs remaining nutrients before excretion.This process takes about 9–12 hours.
The sulfate-methane transition zone (SMTZ) is a zone in oceans, lakes, and rivers found below the sediment surface in which sulfate and methane coexist. The formation of a SMTZ is driven by the diffusion of sulfate down the sediment column and the diffusion of methane up the sediments. At the SMTZ, their diffusion profiles meet and sulfate and methane react with one another, which allows the SMTZ to harbor a unique microbial community whose main form of metabolism is anaerobic oxidation of methane (AOM). The presence of AOM marks the transition from dissimilatory sulfate reduction to methanogenesis as the main metabolism utilized by organisms.
References
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- ↑ Bryant, M. P.; Wolin, E. A.; Wolin, M. J.; Wolfe, R. S. (1967-01-01). "Methanobacillus omelianskii, a symbiotic association of two species of bacteria". Archiv für Mikrobiologie. 59 (1): 20–31. doi:10.1007/bf00406313. ISSN 0003-9276. PMID 5602458.
- ↑ Iannotti, E. L.; Kafkewitz, D.; Wolin, M. J.; Bryant, M. P. (1973-06-01). "Glucose Fermentation Products of Ruminococcus albus Grown in Continuous Culture with Vibrio succinogenes: Changes Caused by Interspecies Transfer of H2". Journal of Bacteriology. 114 (3): 1231–1240. ISSN 0021-9193. PMC 285387 . PMID 4351387.
- ↑ Greening, Chris; Geier, Renae; Wang, Cecilia; Woods, Laura C.; Morales, Sergio E.; McDonald, Michael J.; Rushton-Green, Rowena; Morgan, Xochitl C.; Koike, Satoshi; Leahy, Sinead C.; Kelly, William J. (October 2019). "Diverse hydrogen production and consumption pathways influence methane production in ruminants". The ISME Journal. 13 (10): 2617–2632. doi:10.1038/s41396-019-0464-2. ISSN 1751-7370. PMC 6776011 . PMID 31243332.
- ↑ Thauer, Rudolf K.; Kaster, Anne-Kristin; Seedorf, Henning; Buckel, Wolfgang; Hedderich, Reiner (2008). "Methanogenic archaea: ecologically relevant differences in energy conservation". Nature Reviews Microbiology. 6 (8): 579–591. doi:10.1038/nrmicro1931. PMID 18587410.
- ↑ Nakamura, Noriko; Lin, Henry C.; McSweeney, Christopher S.; Mackie, Roderick I.; Gaskins, H. Rex (2010-01-01). "Mechanisms of microbial hydrogen disposal in the human colon and implications for health and disease". Annual Review of Food Science and Technology. 1: 363–395. doi:10.1146/annurev.food.102308.124101. ISSN 1941-1413. PMID 22129341.