Polyphasic Characterisation of sp. nov., a New Enteric Bacterium Isolated from the Koala Hindgut.

The genus is comprised of six rarely isolated species within the family. Representatives are Gram-negative motile bacilli, and are typically oxidase-negative, lipase-positive and resistant to colistin and cephalothin. In this study, a putative novel species (designated strain ZA_0188), isolated from the koala hindgut, was characterised using a polyphasic taxonomic approach. Maximum average nucleotide identity (ANI) and 16S ribosomal RNA (rRNA) similarity scores well below thresholds of species demarcation were reported, at 81.1% and 97.9%, respectively. Multilocus phylogenetic analysis indicated strain ZA_0188 was most similar to but divergent from recognised species. The isolate's genomic G+C content was determined as 53.0 mol%, >1% lower than previously reported in . Phenotypically, strain ZA_0188 was distinct from recognised species such as colistin- and cephalothin-sensitive, lipase-, sorbitol-, sucrose-, and Voges-Proskauer-negative, and melibiose-, arabinose-, arginine-, and rhamnose-positive. In preliminary experiments, strain ZA_0188 exhibited cellulase activity and high-level tolerance to eucalyptus oil compared to other enteric species surveyed. Collectively, these findings suggest that strain ZA_0188 represents a novel enteric species, for which the name is proposed.