Tabrizicola oligotrophica sp. nov. and Rhodobacter tardus sp. nov., two new species of bacteria belonging to the family Rhodobacteraceae

Abstract

Two Gram-stain-negative, aerobic, non-motile bacteria, designated KMS-5T and CYK-10T, were isolated from freshwater environments. 16S rRNA gene sequence similarity results indicated that these two novel strains belong to the family Rhodobacteraceae . Strain KMS-5T is closely related to species within the genus Tabrizicola (96.1–96.8 % sequence similarity) and Cypionkella (96.5–97.0 %). Strain CYK-10T is closest to Rhodobacter thermarum YIM 73036T with 96.6 % sequence similarity. Phylogenetic analyses based on 16S rRNA gene sequences and an up-to-date bacterial core gene set showed that strain KMS-5T is affiliated with species in the genus Tabrizicola and strain CYK-10T is placed in a distinct clade with Rhodobacter blasticus ATCC 33485T, Rhodobacter thermarum YIM 73036T and Rhodobacter flagellatus SYSU G03088T. These two strains shared common chemotaxonomic features comprising Q-10 as the major quinone, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylcholine as the principal polar lipids, and C18 : 1  ω7c as the main fatty acid. The average nucleotide identity, average amino acid identity and digital DNA–DNA hybridization values between these two novel isolates and their closest relatives were below the cut-off values of 95–96, 90 and 70 %, respectively, used for species demarcation. The obtained polyphasic taxonomic data suggested that strain KMS-5T represents a novel species within the genus Tabrizicola , for which the name Tabrizicola oligotrophica sp. nov. is proposed with KMS-5T (=BCRC 81196T=LMG 31337T) as the type strain, and strain CYK-10T should represent a novel species of the genus Rhodobacter , for which the name Rhodobacter tardus sp. nov. is proposed with CYK-10T (=BCRC 81191T=LMG 31336T) as the type strain.