Mesobacterium hydrothermale sp. nov., isolated from shallow-sea hydrothermal systems off Kueishantao Island

A Gram-negative, rod-shaped, non-motile, aerobic bacterium, designated as strain TK19101^T, was isolated from the intermediate seawater of yellow vent in the shallow-sea hydrothermal system located near Kueishantao Island. The strain was found to grow at 10–40 °C (optimum, 35 °C), at pH 6.0–8.0 (optimum, 7.0), and in 0–5% (w/v) NaCl (optimum, 1%). Strain TK19101^T was catalase-positive and oxidase-positive. The predominant fatty acids (> 10%) in strain TK19101^T cells were C_16:0, summed feature 8 (C_18:1 ω6c and/or C_18:1 ω7c), and C_18:0. The predominant isoprenoid quinone of strain TK19101^T was ubiquinone-10. The polar lipids of strain TK19101^T comprised phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, phospholipid, and unknown polar lipid. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain TK19101^T belonged to the genus Mesobacterium. Strain TK19101^T exhibited highest 16S rRNA gene sequence similarity value to Mesobacterium pallidum MCCC M24557^T (97.48%). The estimated average nucleotide identity and digital DNA-DNA hybridization values between strain TK19101^T and the closest related species Mesobacterium pallidum MCCC M24557^T were 74.88% and 20.30%, respectively. The DNA G + C content was 63.49 mol%. On the basis of the analysis of 16S rRNA gene sequences, genotypic and phylogenetic data, strain TK19101^T has a unique phylogenetic status and represents a novel species of genus Mesobacterium, for which the name Mesobacterium hydrothermale sp. nov. is proposed. The type strain is TK19101^T (= MCCC 1K08936^T = KCTC 8354^T).