Stenotrophomonas is a genus of Gram-stain-negative bacteria commonly found in the environment, while the species Stenotrophomonas maltophilia is an opportunistic pathogen with intrinsic resistance to carbapenems. A Gram-stain-negative rod-shaped bacterial strain, designated 9A T , was isolated from the faecal material of a wild turtle in Wisconsin. The genome of the isolate was sequenced by Illumina whole-genome sequencing. Ribosomal multilocus sequence typing showed that it belonged to the Stenotrophomonas genus without a match to a valid species. In addition, Tetra Correlation Search results showed that the valid species with the highest Z -score (0.98784) was Stenotrophomonas forensis DFS-20110405 T . The 16S rRNA gene pairwise sequence analysis showed that the closest species was Stenotrophomonas lactitubi M15 T with a similarity percentage of 99.57%. However, whole-genome and phylogenomic analyses showed that strain 9A T represented a novel species within the genus Stenotrophomonas . The species that had the highest digital DNA–DNA hybridization (dDDH) and average nucleotide identity based on blast+ (ANIb) values between strain 9A T and type strains of other valid Stenotrophomonas species was S. forensis DFS-20110405 T , with a dDDH value of 34.4% and an ANIb value of 87.29%. Both values are below the accepted species cutoff values of 70% and 95%, respectively. Fatty acid analysis revealed that the most prevalent cellular fatty acid was iso-C 15 : 0 (32.4%), which is consistent with other members of the genus Stenotrophomonas . In addition, C 16 : 0 (8.8%), anteiso-C 15 : 0 (8.6%) and products present in summed feature 3 C 16 : 1 ω7 c / C16 : 1 ω6 c (9.6%) were present in moderate amounts. In silico screening for polar lipid biosynthesis identified enzymes associated with the biosynthesis of phosphatidylserine and phosphatidylethanolamine and diphosphatidylglycerol, respectively. Based on biochemical, phylogenetic, genotypic and chemotaxonomic criteria, the isolate represents a novel species of the genus Stenotrophomonas for which the name Stenotrophomonas testudinis sp. nov. is proposed. The type strain of this species is strain 9A T (=CCUG 77186 T =ATCC TSD-430 T ).
Grachan et al. (Mon,) studied this question.