Methanogens are microorganisms that produce methane as a metabolic byproduct in hypoxic conditions. They belong to the domain of archaea, they are common in wetlands, where they are responsible for marsh gas, in the digestive tracts of animals such as ruminants and 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 termed methanogenesis, is 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. Methanogens are bacilli. There are over 50 described species of methanogens, which do not form a monophyletic group, although all known methanogens belong to Archaea, they are anaerobic organisms that cannot function under aerobic conditions, but a species has been identified that can function in anoxic microsites within aerobic environments.
They are sensitive to the presence of oxygen at trace level. They cannot sustain oxygen stress for a prolonged time. However, Methanosarcina barkeri is exceptional in possessing a superoxide dismutase enzyme, may survive longer than the others in the presence of O2; some methanogens, called hydrogenotrophic, use carbon dioxide as a source of carbon, hydrogen as a reducing agent. The reduction of carbon dioxide into methane in the presence of hydrogen can be expressed as follows: CO2 + 4 H2 → CH4 + 2H2OSome of the CO2 reacts with the hydrogen to produce methane, which creates an electrochemical gradient across the cell membrane, used to generate ATP through chemiosmosis. In contrast and algae use water as their reducing agent. Methanogens lack peptidoglycan, a polymer, found in the cell walls of Bacteria but not in those of Archaea; some methanogens have a cell wall, composed of pseudopeptidoglycan. Other methanogens do not, but have at least one paracrystalline array made up of proteins that fit together like a jigsaw puzzle.
Methanogens play a vital ecological role in anaerobic environments of removing excess hydrogen and fermentation products that have been produced by other forms of anaerobic respiration. Methanogens thrive in environments in which all electron acceptors other than CO2 have been depleted. In deep basaltic rocks near the mid ocean ridges, they can obtain their hydrogen from the serpentinisation reaction of olivine as observed in the hydrothermal field of Lost City; the thermal breakdown of water and water radiolysis are other possible sources of hydrogen. Methanogens are key agents of remineralization of organic carbon in continental margin sediments and other aquatic sediments with high rates of sedimentation and high sediment organic matter. Under the correct conditions of pressure and temperature, biogenic methane can accumulate in massive deposits of methane clathrates, which account for a significant fraction of organic carbon in continental margin sediments and represent a key reservoir of a potent greenhouse gas.
Methanogens have been found in several extreme environments on Earth – buried under kilometres of ice in Greenland and living in hot, dry desert soil. They are known to be the most common archaebacteria in deep subterranean habitats. Live microbes making methane were found in a glacial ice core sample retrieved from about three kilometres under Greenland by researchers from the University of California, Berkeley, they found a constant metabolism able to repair macromolecular damage, at temperatures of 145 to –40 °C. Another study has discovered methanogens in a harsh environment on Earth. Researchers studied dozens of soil and vapour samples from five different desert environments in Utah and California in the United States, in Canada and Chile. Of these, five soil samples and three vapour samples from the vicinity of the Mars Desert Research Station in Utah were found to have signs of viable methanogens; some scientists have proposed that the presence of methane in the Martian atmosphere may be indicative of native methanogens on that planet.
In June 2019, NASA’s Curiosity rover detected methane generated by underground microbes such as methanogens, which signals possibility of life on Mars. Related to the methanogens are the anaerobic methane oxidizers, which utilize methane as a substrate in conjunction with the reduction of sulfate and nitrate. Most methanogens are autotrophic producers, but those that oxidize CH3COO− are classed as chemotroph instead. Comparative genomic analysis has led to the identification of 31 signature proteins which are specific for methanogens. Most of these proteins are related to methanogenesis, they could serve as potential molecular markers for methanogens. Additionally, 10 proteins found in all methanogens which are shared by Archaeoglobus, suggest that these two groups are related. In phylogenetic trees, methanogens are not monophyletic and they are split into three clades. Hence, the unique shared presence of large numbers of proteins by all methanogens could be due to lateral gene transfers. Methanogens are known to produce methane from substrates such as H2/CO2, formate and methylamines in a process called methanogenesis.
Different methanogenic reactions are catalyzed by unique sets of coenzymes. While reaction mechanism and energetics vary between one reaction and another, all of these reactions
The 2010–11 Liga Nacional de Ascenso de Honduras season is the 32nd season of the Liga Nacional de Ascenso de Honduras, the second division of football in Honduras. It is contested by 28 teams split into two zones with two divisions each; the season is split into the Apertura and the Clausura. After the end of the Clausura, the winners of both competitions will face off against each other in order to determine the team which will earn promotion to the Liga Nacional de Fútbol de Honduras for the 2011–12 season. Parrillas One advanced 4–1 on aggregated score. Yoro advanced 3–0 on aggregated score. Atlético Municipal advanced 4–3 on aggregated score. Atlético Esperanzano advanced 5–2 on aggregated score. Parrillas One advanced 3–1 on aggregated score. Yoro advanced 4–3 on aggregated score. Parrillas One won 3–2 on aggregated score. Real Sociedad advanced 3–0 on aggregate score. Atlético Choloma advanced 1–0 on aggregate score. Yoro advanced 7–2 on aggregate score. Atlético Municipal advanced 3–2 on aggregate score.
Atlético Choloma 3–3 Yoro on aggregate score. Real Sociedad won 3–2 on aggregate score. Real Sociedad 3–3 Atlético Choloma on aggregate score. To be played between Parrillas One and Atlético Choloma, winners of Apertura and Clausura tournaments respectively. Atlético Choloma won 2–1 on aggregate score
Astro Bella was a television channel by the Malaysian satellite provider Astro on channel 133. When it began broadcasting on 5 March 2012, the channel broadcast telenovelas, the first channel of its kind in Malaysia; the channel was broadcast on the channel number used B4U, a Bollywood movie channel.. The channel was included in the network's Mustika package; the channel contain telenovelas from the Philippines, Thailand, Latin America, Portugal, Poland, Spain and Italy. While most telenovelas were broadcast in their original audio with Bahasa Malaysia subtitles, some of them were broadcast with dubbing in the native language. Selected telenovelas were broadcast in HD on Astro Mustika HD. Several locally produced dramas aired on Astro Mustika HD are available on Astro Bella, their programs expanded during September–October 2015 to include lifestyle programs, such as travel and cooking, in addition to telenovelas. The channel ends its broadcast at midnight on 1 October 2018, its programs move back to Astro Prima, with some programs moving to other channels within Astro's Malay channels as well.
Below is a first list of scheduled series in Astro Bella: List of programmes broadcast by Astro Bella Astro Bella TV Guide