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Archaea are environmental organisms that are associated with the mucosa in mammals. In humans, Archaea are associated with the vaginal, oral, and intestinal mucosa. Because of the fastidious nature of these strict anaerobes, most current knowledge about the archaeal flora of mammals is derived from DNA-based analyses. In the human gut, methanogenic Archaea metabolize major fermentation products, such as alcohols, short chain organic acids, carbon dioxide (CO2), and hydrogen (H2). Until recently, the diversity of gut methanogens was thought to be limited to two species: Methanobrevibacter smithii, the most abundant methanogenic Archaea found in the human gut, and Methanosphaera stadtmanae, which is seldom detected in the human gut. In the gut, M. smithii converts H2, CO2, and formate into CH4 using carbon as the terminal electron acceptor; this redox reaction sustains anaerobic respiration, which allows for the production of ATP. This archaeon can also remove fermentation end products, such as methanol and ethanol, produced by other bacteria lacking a methanogenic pathway. [PMID: 19759898]
Methanobrevibacter smithii may impact human health, but its beneficial effect is still questionable. [PMID: 29449383] In the gut, M. smithii converts H2, CO2, and formate into CH4 using carbon as the terminal electron acceptor; this redox reaction sustains anaerobic respiration, which allows for the production of ATP. Until recently, the diversity of gut methanogens was thought to be limited to two species: Methanobrevibacter smithii, the most abundant methanogenic Archaea found in the human gut, and Methanosphaera stadtmanae, which is seldom detected in the human gut. This archaeon can also remove fermentation end products, such as methanol and ethanol, produced by other bacteria lacking a methanogenic pathway. [PMID: 19759898]
Methanobrevibacter smithii (strain ATCC 35061 / DSM 861) is a methanogenic Euryarchaeote which is the dominant archeon in the human gut ecosystem and makes up 10% of all anaerobes in the colons of healthy adults. Studies in gnotobiotic mice indicate that M. smithii affects the specificity and efficiency of bacterial digestion of dietary polysaccharide, thereby influencing host calorie harvest and adiposity. Comparison of the gut microbial communities of genetically obese and lean mice has shown that the former contain an enhanced representation of genes involved in polysaccharide degradation, possess more archaea and exhibit a greater capacity to promote adiposity when transplanted in germ-free recipients. These findings suggest that M. smithii may be a therapeutic target for reducing energy harvest in obese humans. [UP000001992]
Methanobrevibacter is a fastidious archaeal microorganism and obligate anaerobe. It can be cultivated in a pressurized anaerobic atmosphere of 80% hydrogen and 20% carbon dioxide. Among Methanobrevibacter species, M. smithii is a near-ubiquitous resident of the human intestinal microbiome. The prevalence of methanogens in humans has been reported to be dependent on the age of the human host; populations increase gradually throughout childhood, reaching a maximum abundance level in adults. A methanogenic strain, KB11, was purified from the feces of a healthy 43-year-old Korean male. This is the first human gut methanogen isolated from South Korea. [PMID: 29449383]
| Lineage | Physiology | General | Growth Tolerances | Hydrol./digest./degr. |
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Health: Unknown
Source: human faeces (gut) and sludge
DNA G+C(%): 30.6
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Opt. T: 37-39℃
Opt. pH: 6.9-7.4
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| Monosaccharide util/assim | Oligosaccharide util/assim | Other carboh. util/assim | Amino acid util/assim | Organic acid util/assim |
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