| Abstract |
Two Gram-negative, aerobic strains, Y215(T) and Y226(T), were isolated from sediment from Yueqing Bay, Zhejiang Province, China. The two novel strains were both positive for oxidase activity, nitrate reduction, and aesculin and casein decomposition, but negative for gelatin and tyrosine decomposition. Catalase activity, and starch and Tween 80 decomposition differed between the two strains. Cells of both novel strains were rod-shaped in young cultures and ovoid in older cultures. Optimum NaCl concentration and pH range for growth of both strains were 2.0-3.0% (w/v) and 7.0-8.0, respectively, whereas the optimum growth temperature for strain Y215(T) (25-30 °C) was lower than that for strain Y226(T) (30-37 °C). The genomic DNA G+C contents of strains Y215(T) and Y226(T) were 54.0 and 56.7 mol%, respectively. The major fatty acids in both isolates were iso-C(15:0) and iso-C(17:1)ω9c, which was also the case in the reference strains apart from Microbulbifer salipaludis, which possessed C(18:1)ω7c as the predominant fatty acid. The predominant isoprenoid quinone was Q-8 and the major polar lipids of both strains were phosphatidylethanolamine, phosphatidylglycerol and an unknown glycolipid. Both strains had highest 16S rRNA gene sequence similarity to members of the genus Microbulbifer. Strain Y215(T) was closely related to the type strains of Microbulbifer maritimus (97.6%) and Microbulbifer donghaiensis (97.5%), whereas strain Y226(T) was closely related to the type strain of M. salipaludis (97.6%). Phylogenetic analysis based on 16S rRNA gene sequences showed that strains Y215(T) and Y226(T) fell into two separate clusters. The DNA-DNA relatedness values of strain Y215(T) with M. maritimus TF-17(T) and M. donghaiensis CN85(T) were 34.1 and 32.8%, respectively, whereas that between strain Y226(T) and M. salipaludis SM-1(T) was 38.0%; these values are significantly lower than the threshold value for the delineation of bacterial species. On the basis of their distinct taxonomic characteristics, the two isolates represent two novel species of the genus Microbulbifer, for which the names Microbulbifer marinus sp. nov. and Microbulbifer yueqingensis sp. nov. are proposed; the type strains are Y215(T) (=CGMCC 1.10657(T)=JCM 17211(T)) and Y226(T) (=CGMCC 1.10658(T)=JCM 17212(T)), respectively.
|
