Fibrobacteres is a small bacterial phylum which includes many of the major rumen bacteria, allowing for the degradation of plant-based cellulose in ruminant animals. Members of this phylum were categorized in other phyla. The genus Fibrobacter (the only genus of Fibrobacteres) was removed from the genus Bacteroides in 1988.
Phylogeny and Comparative Genomic Studies 
Although Fibrobacteres, which consists of a single genus Fibrobacter containing two species, is currently recognized as a distinct phylum, phylogenetic studies based RpoC and Gyrase B protein sequences, indicate that Fibrobacter succinogenes is closely related to the species from the phyla Bacteroidetes and Chlorobi. The species from these three phyla also branch in the same position based upon conserved signature indels in a number of important proteins. Lastly and most importantly, comparative genomic studies have identified two conserved signature indels (a 5-7 amino acid insert in the RpoC protein and a 13-16 amino acid insertion in serine hydroxymethyltransferase) and one signature protein (PG00081) that are uniquely shared by all of the species from these three phyla. All of these results provide compelling evidence that the species from these three phyla shared a common ancestor exclusive of all other bacteria and it has been proposed that they should all recognized as part of a single “FCB”superphylum.
- Class Fibrobacteres
The phylum Fibrobacteres is considered to be closely related to the CFB [Cytophaga-Flavibacterium-Bacteroides]. The only genus in this phylum is Fibrobacter that contains strains from the guts of many mammals including cattle and pigs. The two described species in this genus namely, Fibrobacter succinogenes and Fibrobacter intestinalis are important members of fibrolytic communities in mammalian guts and have received a lot of attention in recent decades due to the long-standing interest microbes capable of degrading plant fiber.
Molecular evidence based on the amplification of 16rRNA genes from various environments suggest that the phylum is much more widespread than previously thought. Most of the clones from mammalian environments group along with the known isolates in what has been called Fibrobacteres subphylum 1. Members of Fibrobacteres subphylum 2 however, have so far been found only in the gut of termites. Due to the lack of cultured representatives from subphylum 2, it is so far unclear as to the role they might play in termite guts.
See also 
- Montgomery L; Flesher B; Stahl D. (1988). "Transfer of Bacteroides succinogenes (Hungate) to Fibrobacter gen. nov. as Fibrobacter succinogenes comb. nov. and description of Fibrobacter intestinalis sp. nov". Int. J. Syst. Bacteriol. 38 (4): 430–435. doi:10.1099/00207713-38-4-430.
- Gupta, R. S. (2004). The phylogeny and signature sequences characteristics of Fibrobacteres, Chlorobi, and Bacteroidetes. Critical Reviews in Microbiology. 30:123-140. doi: 10.1080/10408410490435133.
- Griffiths E, Gupta RS. (2001) The use of signature sequences in different proteins to determine the relative branching order of bacterial divisions: evidence that Fibrobacter diverged at a similar time to Chlamydia and the Cytophaga- Flavobacterium-Bacteroides division. Microbiology,147:2611-22.
- Gupta, R. S. and Lorenzini, E. (2007). Phylogeny and molecular signatures (conserved proteins and indels) that are specific for the Bacteroidetes and Chlorobi species. BMC Evolutionary Biology. 7:71. doi:10.1186/1471-2148-7-71.
- J.P. Euzéby. "Fibrobacteres". List of Prokaryotic names with Standing in Nomenclature. Retrieved 2011-06-05.
- Qi, M. and Nelson, K.E. and Daugherty, S.C. and Nelson, W.C. and Hance, I.R. and Morrison, M. and Forsberg, C.W. (2005). "Novel molecular features of the fibrolytic intestinal bacterium Fibrobacter intestinalis not shared with Fibrobacter succinogenes as determined by suppressive subtractive hybridization". Journal of bacteriology 187 (11): 3739.
- McDonald, J.E. and Lockhart, R.J. and Cox, M.J. and Allison, H.E. and McCarthy, A.J. (2008). "Detection of novel Fibrobacter populations in landfill sites and determination of their relative abundance via quantitative PCR". Environmental microbiology (Wiley Online Library) 10 (5): 1310–1319.
- Hongoh, Y. and Deevong, P. and Hattori, S. and Inoue, T. and Noda, S. and Noparatnaraporn, N. and Kudo, T. and Ohkuma, M. (2006). "Phylogenetic diversity, localization, and cell morphologies of members of the candidate phylum TG3 and a subphylum in the phylum Fibrobacteres, recently discovered bacterial groups dominant in termite guts". Applied and environmental microbiology (Am Soc Microbiol) 72 (10): 6780–6788.
- Holt JG (editor) (1994). Bergey's Manual of Determinative Bacteriology (9th ed.). Williams & Wilkins. ISBN 0-683-00603-7.
- List of Prokaryotic Names with Standing in Nomenclature - Genus Fibrobacter
- Systema Naturae 2000 Classification: Phylum Fibrobacteres