Microbulbifer spongiae sp. nov., isolated from marine sponge Diacarnus erythraeanus

A novel bacterium, designated as MI-G^T, was isolated from marine sponge <i>Diacarnu</i>s <i>erythraeanus</i>. Cells of strain MI-G^T are Gram-stain-negative, aerobic, and rod or coccoid-ovoid in shape. MI-G^T is able to grow at 10-40 °C (optimum, 28 °C), with 1.0-8.0% (w/v) NaCl (optimum, 4.0%), and at pH 5.5-9.0 (optimum, pH 8.0). The 16S rRNA gene sequence of strain MI-G^T shows 98.35, 97.32 and 97.25% similarity to those of <i>Microbulbifer variabilis</i> Ni-2088^T, <i>Microbulbifer maritimus</i> TF-17^T and <i>Microbulbifer echini</i> AM134^T, respectively. Phylogenetic analysis also exhibits that strain MI-G^T falls within a clade comprising members of the genus <i>Microbulbifer</i> (class <i>Gammaproteobacteria</i>). The genome size of strain MI-G^T is 4478124 bp with a G+C content of 54.51 mol%. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain MI-G^T and other type strains are 71.61-76.44% (ANIb), 83.27-84.36% (ANIm) and 13.4-18.7% (dDDH), respectively. These values are significantly lower than the recommended threshold values for bacterial species delineation. Percentage of conserved proteins and average amino acid identity values among the genomes of strain MI-G^T and other closely related species are 52.04-59.13% and 67.47-77.21%, respectively. The major cellular fatty acids of MI-G^T are composed of summed feature 8 (C_{18 : 1} <i>ω</i>7<i>c</i> or C_{18 : 1} <i>ω</i>6<i>c</i>), iso-C_{11 : 0} 3-OH, iso-C_{15 : 0}, C_{16 : 0}, and summed feature 9 (C_{17 : 1} iso <i>ω</i>9<i>c</i> or C_{16 : 0} 10-methyl). The polar lipids of MI-G^T mainly consist of phosphatidylethanolamine, phosphatidylglycerol, aminolipid, and two glycolipids. The major respiratory quinone is Q-8. Based on differential phenotypic and phylogenetic data, strain MI-G^T is considered to represent a novel species of genus <i>Microbulbifer</i>, for which the name <i>Microbulbifer spongiae</i> sp. nov. is proposed. The type strain is MI-G^T (=MCCC 1K07826^T=KCTC 8081^T).