Thiomicrorhabdus marina sp.nov., an obligate chemolithoautotroph isolated from tidal zone sediment, and genome insight into the genus Thiomicrorhabdus

The contribution of microbes to the marine sulfur cycle has received considerable attention in recent years. In this study, a new Gram-stain-negative, aerobic sulfur-oxidizing bacterium, designated strain 6S2-11T, was isolated from tidal zone sediment of the coast of Weihai, China. Strain 6S2-11T was an obligate chemolithoautotroph utilizing thiosulfate as the energy source. Physiological and biochemical experiments, phylogenetic analysis, and comparative genomic analysis were done with strain 6S2-11T. According to genomic analysis, strain 6S2-11T owned a complete thiosulfate oxidation pathway and an untypical nitrogen metabolism pathway. Its relatively small genome also has multiple environmental adaptation mechanisms. The DNA G+C content of strain 6S2-11T was 44.1%. Strain 6S2-11T was observed to grow at 20-37°C (optimum, 35°C), pH 6.0-9.5 (optimum, pH 7.5), and 0.5-5% (w/v) NaCl (optimum, 2.5%). The major cellular fatty acids (>10%) of strain 6S2-11T were Summed Feature 8 (C18:1ω7c/C18:1ω6c), C16:0 and Summed Feature 3 (C16:1ω7c/C16:1ω6c). The comparison of 16S rRNA gene sequences indicated that strain 6S2-11T was most closely to Thiomicrorhabdus xiamenensis G2T (96.8%). Based on the results of phylogenetic analysis, the strain 6S2-11T is a novel specie of the genus Thiomicrorhabdus, for which name Thiomicrorhabdus marina sp.nov. is proposed with the type strain 6S2-11T (=MCCC 1H00523T=KCTC 82994T).