Microbulbifer hainanensis sp. nov., a moderately halopilic bacterium isolated from mangrove sediment.

A new bacterium was successfully isolated from a mangrove sediment sample in Haikou City, Hainan Province, China. The organism is a Gram-negative, rod-shaped, non-motile and strictly aerobic bacterium, named NBU-8HK146. Strain NBU-8HK146 was able to grow at temperatures of 10-40 °C, at salinities of 0-11% (w/v) and at pH 5.5-9.5. Veoges-Proskauer, methyl red reaction and hydrolysis of Tween 20 were negative. Catalase and oxidase activities, HS production, hydrolysis of starch, casein, Tweens 40, 60 and 80 were positive. The major cellular fatty acids were C, iso-C and summed feature 9. The major respiratory quinone was ubiquinone-8 (Q-8). The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol and two unidentified glycolipids. According to 16S rRNA gene sequence similarities, strain NBU-8HK146 shared 98.0%, 97.9%, 97.7%, 97.6% and 97.3% similarities to the species with validated name Microbulbifer taiwanensis CC-LN1-12, Microbulbifer rhizosphaerae Cs16b, Microbulbifer marinus Y215, Microbulbifer donghaiensis CN85 and Microbulbifer aggregans CCB-MM1, respectively. Phylogenetic analyses indicated that strain NBU-8HK146 formed a distinct lineage with strains Microbulbifer taiwanensis CC-LN1-12 and Microbulbifer marinus Y215. Both digital DNA-DNA hybridization values (19.5-22.7%) and average nucleotide identity values (73.2-78.9%) between strain NBU-8HK146 and related species of genus Microbulbifer were below the species delineation cutoffs. The DNA G+C content was 58.9 mol%. Many proteins involving in the adaption of osmotic stress in the salt environment of mangrove were predicted in genome of strain NBU-8HK146. From phenotypic, genotypic, phylogenetic and chemotaxonomic characteristics, strain NBU-8HK146 can be regarded as a new Microbulbifer species for which the name Microbulbifer hainanensis. The type strain is NBU-8HK146 (= KCTC 82226 = MCCC 1K04737).