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

Abstract

Two novel Gram-stain-negative, chemoheterotrophic and strictly aerobic bacteria, strains GY2T and SPO729T, 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 SPO729T [2–3 % (w/v)] was slightly higher than that for strain GY2T (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 GY2T and SPO729T 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 GY2T and SPO729T formed tight phyletic lineages with members of the genus Microbulbifer . Strain GY2T was closely related to Microbulbifer okinawensis ABABA23T (98.2 %), strain SPO729T (98.0 %) and Microbulbifer donghaiensis CN85T (97.0 %); strain SPO729T was closely related to M. okinawensis ABABA23T (98.3 %) and M. donghaiensis CN85T (98.2 %). The DNA–DNA relatedness values of strain GY2T with M. okinawensis ABABA23T, strain SPO729T and M. donghaiensis CN85T were 40.0±2.1 %, 13.1±3.9 % and 16.2±5.8 %, respectively, whereas those of strain SPO729T with M. okinawensis ABABA23T and M. donghaiensis CN85T 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 GY2T and SPO729T 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 GY2T ( = KACC 16189T = JCM 17800T) and SPO729T ( = KCCM 42667T = JCM 14507T), respectively.