Fibrobacteres is a small bacterialphylum which includes many of the major rumen bacteria, allowing for the degradation of plant-basedcellulose in ruminant animals. Members of this phylum were categorized in other phyla. The genusFibrobacter was removed from the genus Bacteroides in 1988.
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 and one signature protein 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 ancestorexclusive of all other bacteria and it has been proposed that they should all recognized as part of a single “FCB”superphylum.
**** Species Chitinivibrio alkaliphilus Sorokin et al. 2014
Class Fibrobacteria Spain et al. 2012
* Order "Candidatus Fibromonadales" ♠ Abdul Rahman et al. 2016
** Family "Candidatus Fibromonadaceae" ♠ Abdul Rahman et al. 2016
*** Genus "Candidatus Fibromonas" ♠ Abdul Rahman et al. 2016
**** Species "CandidatusFibromonas termitidis" ♠ Abdul Rahman et al. 2016
* Order Fibrobacterales Spain et al. 2012
** Family Fibrobacteraceae Spain et al. 2012
*** Genus Fibrobacter Montgomery et al. 1988
**** Species F. intestinalis Montgomery et al. 1988
**** Species F. succinogenes Montgomery et al. 1988
***** Subspecies F. s. elongatus Montgomery et al. 1988
***** Subspecies F. s. succinogenes Montgomery et al. 1988
Notes: ♠ Strains found at the NationalCenter for Biotechnology Information but not listed in the List of Prokaryotic names with Standing in Nomenclature
Distribution
The phylum Fibrobacteres is considered to be closely related to the CFB . 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. and in some litter-feeding cockroaches. The predominance of Fibrobacteres subphylum 2 in cellulolytic fibre-associated bacterial communities in hindguts of wood-feeding Nasutitermes corniger suggests that they play an important role in the breakdown of plant material in higher termites.
