Nitratireductor aquimarinus sp. nov., isolated from a culture of the diatom Skeletonema costatum, and emended description of the genus Nitratireductor

Abstract

Two Gram-negative-staining, aerobic bacterial strains, designated CL-SC21(T) and CL-SC22, were isolated from a culture of the diatom Skeletonema costatum (Korean Marine Microalgae Culture Center, KMMCC strain B-396) established from the East Sea, Korea. The two novel strains shared 99.9 % 16S rRNA gene sequence similarity. Analysis of the 16S rRNA gene sequences showed an affiliation with the genus Nitratireductor, with the strains sharing 96.5-97.5 % similarity with the type strains of recognized species of the genus Nitratireductor and being most closely related to Nitratireductor aquibiodomus NL21(T). Phylogenetic analyses of the 16S rRNA gene sequences showed that strain CL-SC21(T) together with strain CL-SC22 belonged to the genus Nitratireductor and formed a robust clade among closely related Nitratireductor species. The polar lipids comprised phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, two unidentified aminophospholipids, an unidentified aminolipid, an unidentified phospholipid and five unidentified lipids. Ubiquinone 10 was the major quinone. The major cellular fatty acids of strains CL-SC21(T) and CL-SC22 were C(18 : 1)ω7c (70.6-72.3 %) and C(19 : 0)ω8c cyclo (10.9-11.8 %). The genomic DNA G+C contents of strains CL-SC21(T) and CL-SC22 were 56.7 and 57.1 mol%, respectively. The level of DNA-DNA relatedness between strains CL-SC21(T) and CL-SC22 was 86 % (reciprocal 91 %), indicating that the two isolates represented a single species. However, levels of DNA-DNA relatedness between N. aquibiodomus NL21(T) and strains CL-SC21(T) and CL-SC22 were 28 % (reciprocal 45 %) and 25 % (reciprocal 50 %), respectively. Phylogenetic analysis and the results of biochemical tests showed that strains CL-SC21(T) and CL-SC22 were different from all recognized species of the genus Nitratireductor. Thus, strains CL-SC21(T) and CL-SC22 represent a novel species of the genus Nitratireductor, for which the name Nitratireductor aquimarinus sp. nov. is proposed. The type strain is CL-SC21(T) ( = KCCM 90090(T) = JCM 17288(T)).