[7] Although the Oscillospiraceae are largely gram-negative bacteria, Faecalibacterium prausnitzii resembles a gram-positive bacterium in its staining.
[8] 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.
In healthy adults, Faecalibacterium prausnitzii represent approximately 5% of the total fecal microbiota but this can increase to around 15% in some individuals, making it one of the commonest of the gut bacteria.
Since butyrate inhibits the production of NF-kB and IFN-y, both involved in the pro-inflammatory response, Faecalibacterium prausnitzii acts as an anti-inflammatory gut bacterium.
[13][14][15] By blocking the NF-kB pathway, F. prausnitzii indirectly inhibts the production of the pro-inflammatory IL-8, secreted by the intestinal epithelial cells.
[16] Other research has shown that there is a correlation between high populations of Faecalibacterium prausnitzii, low IL-12 abundance, and higher IL-10 production.
[13][7] Lower than usual levels of F. prausnitzii in the intestines have been associated with Crohn's disease, obesity, asthma and major depressive disorder.
[23] Supernatant of F. prausnitzii has been shown to improve the gut barrier by affecting the permeability of epithelial cells.
B. thetaiotaomicron and Escherichia coli are needed to create a suitable environment for F. prausnitzii by reducing the redox potential and alter the composition of the nutrients.
[32] Combining both the host serological data plus microbiological indicators could serve as good biomarker, since it has been reported that Crohn's disease and ulcerative colitis can be differentiated based on monitoring of F. prausnitzii in conjunction with leukocyte count.