Methanobrevibacter smithii

Methanobrevibacter smithii is a species of archaea, a domain of single-celled microorganisms. These organisms are methanogens, which are capable of producing methane as a metabolic byproduct in anoxic conditions. M. smithii is predominant in the human gut microbiota, playing a significant role in the efficient digestion of complex polysaccharides (dietary fibers).

Taxonomy

Methanobrevibacter smithii is classified under the domain Archaea, phylum Euryarchaeota, class Methanobacteria, order Methanobacteriales, family Methanobacteriaceae, and genus Methanobrevibacter. The species was first isolated and described by D.R. Boone in 1989.

Physiology

M. smithii is a non-motile, gram-positive, rod-shaped archaeon. It is a strict anaerobe, meaning it can only survive in environments devoid of oxygen. Its primary metabolic process is methanogenesis, the production of methane from hydrogen and carbon dioxide. This process is unique to archaea and is a significant contributor to the global methane budget.

Role in Human Gut Microbiota

M. smithii is the most abundant methanogen in the human gut, making up to 10% of the total anaerobic population in some individuals. It plays a crucial role in the digestion of complex polysaccharides by fermenting the end products of bacterial fermentation, such as hydrogen and carbon dioxide, into methane. This symbiotic relationship allows for increased energy extraction from food.

Clinical Significance

Alterations in the abundance of M. smithii have been associated with various health conditions, including obesity, anorexia nervosa, and irritable bowel syndrome (IBS). However, the exact role of M. smithii in these conditions is not yet fully understood and is the subject of ongoing research.

See Also

• Human microbiota
• Methanogenesis
• Archaea