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

A novel bacterium, designated as MI-G T , was isolated from marine sponge Diacarnu s erythraeanus . 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 Microbulbifer variabilis Ni-2088 T , Microbulbifer maritimus TF-17 T and Microbulbifer echini AM134 T , respectively. Phylogenetic analysis also exhibits that strain MI-G T falls within a clade comprising members of the genus Microbulbifer (class Gammaproteobacteria ). 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 ω 7 c or C 18 : 1 ω 6 c ), iso-C 11 : 0 3-OH, iso-C 15 : 0 , C 16 : 0 , and summed feature 9 (C 17 : 1 iso ω 9 c 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 Microbulbifer , for which the name Microbulbifer spongiae sp. nov. is proposed. The type strain is MI-G T (=MCCC 1K07826 T =KCTC 8081 T ).