Microbulbifer discodermiae sp. nov. and Microbulbifer jejuensis sp. nov., isolated from marine sponges

Two Gram-stain-negative, facultatively anaerobic, non-motile and rod-shaped bacterial strains, designated 2201CG32-9^T and 2304DJ12-6^T, were isolated from marine sponges collected in the Republic of Korea. Both strains exhibited catalase and oxidase activities but tested negative for nitrate reduction and indole production. Strain 2201CG32-9^T showed optimal growth at 30 °C and pH 7.0-8.0 in the presence of 3% (w/v) NaCl, whereas strain 2304DJ12-6^T grew optimally at 25 °C, pH 8.0 and 3% (w/v) NaCl. Phylogenetic analysis of the 16S rRNA gene and phylogenomic analysis of genome sequences indicated that strains 2201CG32-9^T and 2304DJ12-6^T represented novel species within the genus <i>Microbulbifer</i>. Based on whole-genome phylogenomic analysis, the two strains were most closely related to <i>Microbulbifer okhotskensis</i> OS29^T and <i>Microbulbifer variabilis</i> ATCC 700307^T, respectively. The average nucleotide identity values of these strains were found to be <75.9%, and their digital DNA-DNA hybridization values were <22.5%. The DNA G+C contents of strains 2201CG32-9^T and 2304DJ12-6^T were 56.5 and 53.5 mol%, respectively. In both strains, ubiquinone-8 was identified as the predominant respiratory quinone, and the major cellular fatty acids (>5.0%) were C_16:0, iso-C_11:0 3-OH, iso-C_15:0, iso-C_17:0, summed feature 8 and summed feature 9. As for polar lipids, both strains comprised phosphatidylglycerol, phosphatidylethanolamine and phosphoglycolipid as common major polar lipids. Strains 2201CG32-9^T and 2304DJ12-6^T are classified as two novel species of the genus <i>Microbulbifer</i> based on a polyphasic taxonomic approach, for which the names <i>Microbulbifer discodermiae</i> sp. nov. (2201CG32-9^T=KACC 23829^T=JCM 37223^T) and <i>Microbulbifer jejuensis</i> sp. nov. (2304DJ12-6^T=KACC 23832^T=MCCC 1K09533^T) are proposed, respectively.