Faecalibacterium

Faecalibacterium is a genus of bacteria. The genus contains several species including Faecalibacterium prausnitzii, Faecalibacterium butyricigenerans, Faecalibacterium longum, Faecalibacterium duncaniae, Faecalibacterium hattorii, and Faecalibacterium gallinarum. Its first known species, Faecalibacterium prausnitzii is gram-positive, mesophilic, rod-shaped, and anaerobic, and is one of the most abundant and important commensal bacteria of the human gut microbiota. It is non-spore forming and non-motile. These bacteria produce butyrate and other short-chain fatty acids through the fermentation of dietary fiber. The production of butyrate makes them an important member of the gut microbiota, fighting against inflammation.

== History == Formerly assigned to the genus Fusobacterium in the phylum Fusobacteriota, Faecalibacterium prausnitzii was re-assigned to its own genus when phylogenetic analysis of isolates showed it to be a member of the phylum Bacillota. It now is regarded as a member of the Oscillospiraceae in Clostridium cluster IV. Although the Oscillospiraceae are largely gram-negative bacteria, Faecalibacterium prausnitzii resembles a gram-positive bacterium in its staining. This can be ascribed to the fact that it lacks lipopolysaccharides in its outer membrane, so that, in its staining, it more closely resembles gram-positive bacteria, than gram-negative.