Description of Catenibacterium mitsuokai subsp. tridentinum subsp. nov., an anaerobic bacterium isolated from human faeces, and emended description of C. mitsuokai

A recent metagenomic survey has revealed an unknown bacterial clade within the <i>Catenibacterium mitsuokai</i> species to be significantly more prevalent in non-urbanized populations, compared to urbanized ones. We isolated and characterized a strain of this clade from the stool of a healthy adult volunteer. Strain CMD8551^T is strictly anaerobic, appears as long chains of Gram-positive rods and produces acetate in the presence of glucose. The lipidomic profile showed a higher proportion of saturated lipid species amongst the detected phospholipids. The whole genome is 2,320,430 bp long and has a G+C content of 33.7 mol% with 2,239 CDSs. A phylogenetic analysis comparing the sequences of the strain CMD8551^T with publicly available reference genomes from the <i>Catenibacterium</i> genus revealed that the CMD8551^T isolate, together with other isolate genomes, forms a distinct subspecies of <i>C. mitsuokai</i> and has an average nucleotide identity lower than 94% with respect to the previously described <i>C. mitsuokai</i> subsp. <i>mitsuokai</i>. Given the phenotypic, chemotaxonomic and phylogenetic characteristics of the newly isolated CMD8551^T (=DSM 118469^T=LMG 33725^T=CIP 112509^T) that clearly differ from those of the <i>C. mitsuokai</i> subsp. <i>mitsuokai</i> type strain RCA14-39^T, we propose it as the type strain of a novel subspecies of <i>C. mitsuokai</i>, with the name <i>C. mitsuokai</i> subsp. <i>tridentinum</i> subsp. nov.