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Bacillus subtilis Gram.jpg
Bacillus subtilis, Gram stained
Scientific classification


The Firmicutes are a phylum of bacteria, most of which have the Gram-positive type of cell walls.

Classes[change | change source]

The group is typically divided into the Clostridia, which are anaerobic, the Bacilli, which are aerobic, and the Mollicutes, a class of bacteria which do not have cell walls.

On phylogenetic trees, the first two groups show up as paraphyletic or polyphyletic, as do their main genera, Clostridium and Bacillus.[1]

Health[change | change source]

Firmicutes make up the largest portion of the mouse and human gut microbiome.[2] The division Firmicutes as part of the gut flora has been shown to be involved in energy resorption and obesity.[3][4][5]

References[change | change source]

  1. Wolf M. et al (2004). "Phylogeny of Firmicutes with special reference to Mycoplasma (Mollicutes) as inferred from phosphoglycerate kinase amino acid sequence data". Int. J. Syst. Evol. Microbiol. 54 (Pt 3): 871–5. doi:10.1099/ijs.0.02868-0. PMID 15143038. 
  2. Ley R.E; Peterson D.A. & Gordon J.I. (2006). "Ecological and evolutionary forces shaping microbial diversity in the human intestine". Cell 124 (4): 837–48. doi:10.1016/j.cell.2006.02.017. PMID 16497592. 
  3. Ley R.E. et al (2006). "Microbial ecology: human gut microbes associated with obesity". Nature 444 (7122): 1022–3. PMID 17183309. 
  4. Henig, Robin Marantz (2006-08-13). "Fat Factors". New York Times Magazine. Retrieved 2008-09-28.
  5. Ley R.E. et al (2005). "Obesity alters gut microbial ecology". Proc. Natl. Acad. Sci. U.S.A. 102 (31): 11070–5. doi:10.1073/pnas.0504978102. PMC 1176910. PMID 16033867. Retrieved 2008-09-28.