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TAXONOMY: Terrabacteria group -> Firmicutes -> Clostridia -> Clostridiales -> Ruminococcaceae -> Faecalibacterium -> Faecalibacterium prausnitzii
'Faecalibacterium' is a genus of bacteria. Its sole known species, 'Faecalibacterium prausnitzii', is an important commensal bacterium of the human gut flora. Faecalibacterium prausnitzii is very special. Mounting evidence suggests that the systemic inflammation observed in obesity does not just result from the accumulation of fat but contributes to it. Scientists at Catholic University of Louvain in Belgium recently showed that adding inulin, a fermentable fiber, to the diet of obese women increased counts of F. prausnitzii and other clostridial bacteria and reduced that dangerous systemic inflammation. Faecalibacterium prausnitzii doesn't metabolize starch at all, preferring to selectively dine on oligosaccharides, pectin and other varied non-starchy fermentable fibers. In healthy adults, Faecalibacterium prausnitzii represent more than 5% of the bacteria in the intestine, making it one of the most common gut bacteria. Lower than usual levels of F. prausnitzii in the intestines have been associated with Crohn's Disease, obesity and asthma. At the species level, butyrate-producing bacterial species, such as Blautia faecis, Roseburia inulinivorans, Ruminococcus torques, Clostridium lavalense, Bacteroides uniformis and Faecalibacterium prausnitzii were significantly reduced in CD patients as compared to healthy individuals (p < 0.05). [PMID: 26789999 ] Identified as constituent of vaginal microbiome. [PMID:23282177]
Faecalibacterium prausnitzii is one of the most abundant commensal bacteria in the healthy human large intestine, but information on genetic diversity and substrate utilization is limited. Most F. prausnitzii strains tested grew well under anaerobic conditions on apple pectin. Furthermore, F. prausnitzii strains competed successfully in coculture with two other abundant pectin-utilizing species, Bacteroides thetaiotaomicron and Eubacterium eligens, with apple pectin as substrate, suggesting that this species makes a contribution to pectin fermentation in the colon. Most strains grew on N-acetylglucosamine, demonstrating an ability to utilize host-derived substrates. All strains tested were bile sensitive, showing at least 80% growth inhibition in the presence of 0.5 μg/ml bile salts, while inhibition at mildly acidic pH was strain dependent. [PMID: 22101049]
Despite being extremely oxygen sensitive, F. prausnitzii is found adherent to the gut mucosa where oxygen diffuses from epithelial cells. This paradox is now explained on the basis of gas tube experiments, flavin-dependent reduction of 5,5′-dithiobis-2-nitrobenzoate and microbial fuel cell experiments. The results show that F. prausnitzii employs an extracellular electron shuttle of flavins and thiols to transfer electrons to oxygen. Both compounds are present in the healthy human gut. These observations may have important implications for the treatment of patients with Crohn's disease, for example, with flavin- or antioxidant rich diets, and they provide a novel key insight in host–microbe interactions at the gut barrier. F. prausnitzii requires riboflavin for electron transfer to the anode of a microbial fuel cell. [PMC 3400418] F. prausnitzii is an extremely oxygen sensitive (EOS) bacterium and is difficult to cultivate even in anaerobic conditions. The major end products of glucose fermentation by F. prausnitzii strains are formate, small amounts of D-lactate (L-lactate being undetectable) and substantial quantities of butyrate (>10 mM butyrate in vitro). Recently, culture medium supplemented with flavins and cysteine or glutathione was shown to support growth of F. prausnitzii under micro-aerobic conditions.
Other possible mechanisms contributing to the protective effect of F. prausnitzii in colitis might be related to its capacity to induce relatively large amounts of IL-10 and low amounts of IL-12 in peripheral blood mononuclear cells. If F. prausnitzii also induces large amounts of IL-10 in mucosal dendritic cells and macrophages, it may contribute to intestinal homeostasis by inhibiting the production of pro-inflammatory cytokines such as IFN-g, TNF-a, IL- 6 and IL-12 and enhancing the suppressive activity of Foxp3+ Tregs in the mucosa. The induction of IL-10 in immune cells by F. prausnitzii may also play a role in shaping T cells responses, in particular in the induction of Tregs in the colon as described for certain other commensals. [PMID: 23831042] Faecalibacterium prausnitzii (of the phylum Firmicutes) were significantly higher in obese than in non-obese children. Decreased count in diabetics. [PMID: 26452391]
This species has been identified as a resident in the human gastrointestinal tract based on the phylogenetic framework of its small subunit ribosomal RNA gene sequences.[PMC 4262072] Identified as a 'core species' of the human gut microbiome. [PMID: 23222524]