Microbulbifer gwangyangensis sp. nov. and Microbulbifer pacificus sp. nov., isolated from marine environments

Two novel Gram-stain-negative, chemoheterotrophic and strictly aerobic bacteria, strains GY2(T) and SPO729(T), were isolated from a tidal flat at Gwangyang Bay in Korea and a marine sponge sample from the Pacific Ocean, respectively. The two strains were halotolerant, catalase- and oxidase-positive, and non-motile rods. Optimum temperature and pH for growth of both strains were observed to be 35 °C and pH 7.0-7.5, but optimum salinity for strain SPO729(T) [2-3 % (w/v)] was slightly higher than that for strain GY2(T) (1-2 %). The major cellular fatty acids of both strains were C16 : 0, iso-C15 : 0, iso-C17 : 0, iso-C17 : 1ω9c, C18 : 1ω7c, iso-C11 : 0 and iso-C11 : 0 3-OH. The genomic DNA G+C contents of strains GY2(T) and SPO729(T) were 55.1 and 57.9 mol%, respectively, and ubiquinone 8 (Q-8) was detected as the sole respiratory quinone from the two strains. Phylogenetic analysis based on 16S rRNA gene sequences showed that strains GY2(T) and SPO729(T) formed tight phyletic lineages with members of the genus Microbulbifer. Strain GY2(T) was closely related to Microbulbifer okinawensis ABABA23(T) (98.2 %), strain SPO729(T) (98.0 %) and Microbulbifer donghaiensis CN85(T) (97.0 %); strain SPO729(T) was closely related to M. okinawensis ABABA23(T) (98.3 %) and M. donghaiensis CN85(T) (98.2 %). The DNA-DNA relatedness values of strain GY2(T) with M. okinawensis ABABA23(T), strain SPO729(T) and M. donghaiensis CN85(T) were 40.0±2.1 %, 13.1±3.9 % and 16.2±5.8 %, respectively, whereas those of strain SPO729(T) with M. okinawensis ABABA23(T) and M. donghaiensis CN85(T) were 48.0±4.0 % and 34.6±9.3 %, respectively. On the basis of phenotypic and molecular features, it is concluded that the two strains GY2(T) and SPO729(T) represent two novel species of the genus Microbulbifer, for which the names Microbulbifer gwangyangensis sp. nov. and Microbulbifer pacificus are proposed; the type strains are GY2(T) ( = KACC 16189(T) = JCM 17800(T)) and SPO729(T) ( = KCCM 42667(T) = JCM 14507(T)), respectively.