As already depicted in the original publication, the type strain of the species Cellulosimicrobium variabile Bakalidou et al. 2002, DSM 10177(T), does not cluster unambiguously with the type species, Cellulosimicrobium cellulans DSM 43879(T), in phylogenetic analysis. Strain DSM 10177(T) is moderately related to the recently described species Xylanimonas cellulosilytica, Promicromonospora pachnodae and Xylanibacterium ulmi, forming a lineage that branches between C. cellulans and members of the genus Promicromonospora in most dendrograms generated on the basis of different algorithms and reference strains. The type strains of the two Cellulosimicrobium species resemble each other in morphology, composition of fatty acids, DNA G+C content, phospholipids and the presence of lysine in position 3 of the peptide subunit of peptidoglycan. However, the two strains differ from each other in cell-wall sugars and in the amino acid composition of the A4alpha-type peptidoglycan, which contains serine and aspartic acid in C. cellulans, whereas only aspartic acid is present in the interpeptide bridge of C. variabile. This type is also present in Xylanimonas cellulosilytica XIL07(T), but not in the neighbouring species P. pachnodae DSM 12657(T), which exhibits the L-lys-L-ser-D-Glu type. On the basis of distinct phylogenetic position and the amino acid composition of peptidoglycan, a novel genus and combination for C. variabile, Isoptericola variabilis gen. nov., comb. nov., is proposed.