Fibrobacterota
Fibrobacterota 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 Fibrobacterota) was removed from the genus "Bacteroides" in 1988. Phylogeny and Comparative Genomic Studies. Although "Fibrobacterota", 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 	Fibrobacterota
17409083	been proposed that they should all recognized as part of a single “FCB”superphylum. Phylogeny. Phylogeny of Fibrobacterota. Taxonomy. The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LSPN) and the National Center for Biotechnology Information (NCBI). Distribution. The phylum Fibrobacterota is considered to be closely related to the CFB [Cytophaga-Flavibacterium-Bacteroidota]. 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 subphylum 1. Members of subphylum 2 however, have so far been found only in the gut of termites. and in some litter-feeding cockroaches. The predominance of 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.