Marinobacter qingdaonensis sp. nov., a moderately halotolerant bacterium isolated from intertidal sediment

A Gram-stain-negative, aerobic, rod-shaped and halotolerant bacterium, designated as strain ASW11-75^T, was isolated from intertidal sediments in Qingdao, PR China, and identified using a polyphasic taxonomic approach. Growth of strain ASW11-75^T occurred at 10-45 °C (optimum, 37 °C), pH 6.5-9.0 (optimum, pH 8.0) and 0.5-18.0 % NaCl concentrations (optimum, 2.5 %). Phylogenetic analyses based on 16S rRNA gene sequences and 1179 single-copy orthologous clusters indicated that strain ASW11-75^T is affiliated with the genus Marinobacter. Strain ASW11-75^T showed highest 16S rRNA gene sequence similarity to 'Marinobacter arenosus' CAU 1620^T (98.5 %). The digital DNA-DNA hybridization and average nucleotide identity values between strain ASW11-75^T and its closely related strains (Marinobacter salarius R9SW1^T, Marinobacter similis A3d10^T, 'Marinobacter arenosus' CAU 1620^T, Marinobacter sediminum R65^T, Marinobacter salinus Hb8^T, Marinobacter alexandrii LZ-8^T and Marinobacter nauticus ATCC 49840^T) were 19.8-24.5 % and 76.6-80.7 %, respectively. The predominant cellular fatty acids were C_16 : 0, C_18 : 1  ω9c and C_16 : 0 N alcohol. The polar lipids were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, one unidentified aminophospholipid and two unidentified lipids. The major isoprenoid quinone was ubiquinone-9. The genomic DNA G+C content was 62.2 mol%. Based on genomic and gene function analysis, strain ASW11-75^T had lower protein isoelectric points with higher ratios of acidic residues to basic residues and possessed genes related to ion transport and organic osmoprotectant uptake, implying its potential tolerance to salt. The results of polyphasic characterization indicated strain ASW11-75^T represents a novel Marinobacter species, for which the name Marinobacter qingdaonensis sp. nov. with the type strain ASW11-75^T is proposed. The type strain is ASW11-75^T (=KCTC 82497^T=MCCC 1K05587^T).