Description of Halodurantibacterium rhizosphaerae sp. nov., a novel bacterium isolated from the rhizosphere, and reclassification of 'Plastorhodobacter daqingensis' as Halodurantibacterium daqingense sp. nov.

Abstract

A Gram-stain-negative, non-motile, spherical bacterium, designated strain LNNU 3342^T, was isolated from the rhizosphere soil of halophyte Suaeda aralocaspica collected in Xinjiang, PR China. Strain LNNU 3342^T revealed the highest 16S rRNA gene sequence similarity with 'Plastorhodobacter daqingensis' CGMCC 1.12750^T (96.51%), followed by Pararhodobacter aggregans DSM 18938^T (96.25%) and less than 95.64% with the type strains of other recognized species. Phylogenetic analyses based on 16S rRNA gene and genome sequences showed that strain LNNU 3342^T formed a clade with Halodurantibacterium flavum CGMCC 1.12756^T and 'Plastorhodobacter daqingensis' CGMCC 1.12750^T. The amino acid identity and percentage of conserved proteins (POCP) analysis indicated that strain LNNU 3342^T and the type strains of genera Halodurantibacterium and 'Plastorhodobacter' should be recognized as a single genus. The genome size of strain LNNU 3342^T was 3,779,330 bp with genomic DNA G+C content of 64.6 mol%. Strain LNNU 3342^T grew at 10-45 °C (optimum, 30-35 °C), at pH 4.0-9.0 (optimum, pH 7.0-8.0) and in the presence of 0-8% (wt/v) NaCl (optimum, 1-3%). Strain LNNU 3342^T contained Q-10 as the major respiratory quinone. The major cellular fatty acids (> 5.0 %) were summed feature 8 (C_18 : 1 ω7c or C_18 : 1 ω6c) (79.2%) and C_18 : 1 ω7c 11-methyl (6.5%). The polar lipids included diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, hydroxy-phosphatidylethanolamine, one unidentified phospholipid and two unidentified lipids. Based on the physiological, biochemical and phylogenetic results, strain LNNU 3342^T represents a novel species of the genus Halodurantibacterium, for which the name Halodurantibacterium rhizosphaerae sp. nov. is proposed. The type strain is LNNU 3342^T (=KCTC 62250^T =CGMCC 1.17106^T). Additionally, we propose the reclassification of 'Plastorhodobacter daqingensis' as Halodurantibacterium daqingense sp. nov.