Psychrobacter aquimaris sp. nov. and Psychrobacter namhaensis sp. nov., isolated from sea water of the South Sea in Korea

Abstract

Two Gram-negative, non-motile, non-spore-forming, slightly halophilic bacterial strains, SW-210(T) and SW-242(T), were isolated from sea water of the South Sea in Korea, and were characterized taxonomically by means of a polyphasic approach. The two isolates grew optimally at 25-30 degrees C and in the presence of 2-3 % (w/v) NaCl. Strains SW-210(T) and SW-242(T) contained Q-8 as the predominant respiratory lipoquinone and C(18 : 1)omega9c as the major fatty acid. The DNA G+C contents of strains SW-210(T) and SW-242(T) were 43.2 and 45.3 mol%, respectively. The 16S rRNA gene sequences of strains SW-210(T) and SW-242(T) were 98.9 % similar, and the mean DNA-DNA relatedness value between them was 24 %. Phylogenetic analysis based on 16S rRNA gene sequences showed that strains SW-210(T) and SW-242(T) form distinct phylogenetic lineages within the radiation of the cluster comprising Psychrobacter species, having 16S rRNA gene sequence similarity levels of 95.9-99.2 % with respect to the type strains of Psychrobacter species. The levels of DNA-DNA relatedness between the two isolates and the type strains of 15 phylogenetically related Psychrobacter species were well below 70 %. On the basis of phenotypic and phylogenetic data and genomic distinctiveness, strains SW-210(T) and SW-242(T) were classified in the genus Psychrobacter as representing two distinct novel species, for which the names Psychrobacter aquimaris sp. nov. (type strain, SW-210(T) = KCTC 12254(T) = DSM 16329(T)) and Psychrobacter namhaensis sp. nov. (type strain, SW-242(T) = KCTC 12255(T) = DSM 16330(T)) are proposed, respectively.