The species has all features of the genus. Additional phylogenetic relatives based on 16S rRNA gene sequences are Ruminiclostridium josui (84.32%), Ruminiclostridium cellulolyticum (84.11%), and Vallitalea guaymasensis (83.95%). Assignment to the genus Pumilibacter was confirmed by a POCP value of 69.7% between the genome of the type strain and that of the type species of the genus, Pumilibacter muris. Cells are very small and coccoid with a diameter of ca. 0.4-0.6 µm when grown on YCFA or mGAM blood agar under anaerobic conditions for 7 days. In total, 155 CAZymes were identified within the genome and only starch was predicted to be utilised as a carbon source. KEGG analysis identified pathways for the production of acetate from acetyl-CoA (EC:2.3.1.8, 2.7.2.1), propionate from propanoyl-CoA (EC:2.3.1.8, 2.7.2.1), L-cysteine and acetate from sulfide and L-serine (EC:2.3.1.30, 2.5.1.47), and L-glutamate from ammonia via L-glutamine (EC:6.3.1.2, 1.4.1.-). Antibiotic resistance was predicted based on the detection of tetracycline-resistant ribosomal protection protein. Ecological analysis suggested that the species is most prevalent within amplicon datasets from the mouse gut (39.9%). The type strain is CLA-AA-M10T. Its G+C content of genomic DNA is 49.6%. It was isolated from a filtered (0.45 µm) caecal suspension of an SPF mouse.