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 3342T, was isolated from the rhizosphere soil of halophyte Suaeda aralocaspica collected in Xinjiang, PR China. Strain LNNU 3342T revealed the highest 16S rRNA gene sequence similarity with 'Plastorhodobacter daqingensis' CGMCC 1.12750T (96.51%), followed by Pararhodobacter aggregans DSM 18938T (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 3342T formed a clade with Halodurantibacterium flavum CGMCC 1.12756T and 'Plastorhodobacter daqingensis' CGMCC 1.12750T. The amino acid identity and percentage of conserved proteins (POCP) analysis indicated that strain LNNU 3342T and the type strains of genera Halodurantibacterium and 'Plastorhodobacter' should be recognized as a single genus. The genome size of strain LNNU 3342T was 3,779,330 bp with genomic DNA G+C content of 64.6 mol%. Strain LNNU 3342T 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 3342T contained Q-10 as the major respiratory quinone. The major cellular fatty acids (> 5.0 %) were summed feature 8 (C18 : 1 ω7c or C18 : 1 ω6c) (79.2%) and C18 : 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 3342T represents a novel species of the genus Halodurantibacterium, for which the name Halodurantibacterium rhizosphaerae sp. nov. is proposed. The type strain is LNNU 3342T (=KCTC 62250T =CGMCC 1.17106T). Additionally, we propose the reclassification of 'Plastorhodobacter daqingensis' as Halodurantibacterium daqingense sp. nov.