Fibrobacter succinogenes

Fibrobacter succinogenes is a cellulolytic bacterium species in the genus Fibrobacter. It is present in the rumen of cattle. Beta glucans are its substrate of choice in the rumen and its products after digestion include formate, acetate and succinate. Fibrobacter succinogenes forms characteristic extensive grooves in crystalline cellulose, and is also rather readily detached from its substrate during sample preparation. 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. Fibrobacter succinogenes and the species from these two other 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 Fibrobacter succinogenes and all of the species from Bacteroidetes and Chlorobi phyla. All of these results provide compelling evidence that Fibrobacter succinogenes shared a common ancestor with Bacteroidetes and Chlorobi species exclusive of all other bacteria, and these species should be recognized as part of a single “FCB”superphylum.