Roseovarius nitratireducens sp. nov., a halotolerant bacterium isolated from a saline lake

A Gram-stain-negative, aerobic, non-motile and ovoid- to rod-shaped bacterial strain, designated TFZT, was isolated from a water sample of a saline lake in Xinjiang, China and subjected to polyphasic taxonomic investigation. Strain TFZT grew at 4–42 °C and pH 6.5–10.0 (optimum, 30 °C and pH 7.0) and with 0.5–18.0 % (w/v) NaCl (optimum, 1.5 %). According to phylogenetic analysis based on 16S rRNA gene sequences, strain TFZT was assigned to the genus Roseovarius with highest 16S rRNA gene sequence similarity of 97.5 % to Roseovarius tolerans EL-172T, followed by Roseovarius azorensis SSW084T (96.6 %) and Roseovarius mucosus DSM 17069T (95.5 %). Digital DNA–DNA hybridization (DDH) and average nucleotide identity (ANI) were determined to evaluate the genomic relationship between strain TFZT and R. tolerans EL-172T. Digital DDH estimation (22.80±2.35 %) as well as ANI (80.1 %) proved the dissimilarity of strain TFZT. Chemotaxonomic analysis showed that strain TFZT contained ubiquinone-10 as the predominant respiratory quinone and possessed summed feature 8 (comprising C18 : 1 ω7c and/or ω6c) and C16 : 0 as the predominant form of fatty acid. The polar lipids of strain TFZT consisted of phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and five unidentified lipids. The DNA G+C content was 65.4 mol% (by genome sequencing). Based on the polyphasic taxonomic characterization, strain TFZT is considered to represent a novel species of the genus Roseovarius , for which the name Roseovarius nitratireducens sp. nov. is proposed (type strain TFZT=MCCC 1K03339T=KCTC 52967T).