Acetivibrio cellulolyticus and Bacteroides cellulosolvens are members of the greater clostridial assemblage.

The nucleotide sequences of the 16S rRNA genes of Acetivibrio cellulolyticus, A. cellulosolvens, and Bacteroides cellulosolvens were determined and shown to be affiliated with the low G + C members of Gram-positive bacteria. The sequences for A. celluolyticus and A. cellulosolvens were revealed to be identical, supporting the proposal by W.D. Murray [Int. J. Syst. Bacteriol. (1986) 36, 314-316] that A. cellulosolvens be correctly classified as A. cellulolyticus. The closest relative to A. cellulolyticus is Clostridium aldrichii, related at 98.5% sequence similarity. B. cellulosolvens and A. cellulolyticus are related at 94.4% sequence similarity.