sp. nov., a novel hydrogen- and sulfur-oxidizing chemolithoautotroph isolated from a deep-sea hydrothermal plume in the Northwestern Indian Ocean.

A novel mesophilic, hydrogen-, and sulfur-oxidizing bacterium, designated strain ST-419, was isolated from a deep-sea hydrothermal vent plume on the Carlsberg Ridge of the Northwestern Indian Ocean. The isolate was a Gram-staining-negative, non-motile and coccoid to oval-shaped bacterium. Growth was observed at 4-50 °C (optimum 37 °C), pH 5.0-8.6 (optimum pH 6.0) and 1.0-5.0 % (w/v) NaCl (optimum 3.0 %). ST-419 could grow chemlithoautotrophically with molecular hydrogen, sulfide, elemental sulfur and thiosulfate as energy sources. Molecular oxygen, nitrate and elemental sulfur could be used as electron acceptors. The predominant fatty acids were Cω7, Cω7 and C. The major polar lipids were phosphatidylethanolamine, diphosphatidylglycerol and phosphatidylglycerol. The respiratory quinone was menaquinone MK-6 and the G+C content of the genomic DNA was 42.4 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that ST-419 represented a member of genus and was most closely related to 1812E, with 97.6 % sequence similarity. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between ST-419 and 1812E were 74.6 and 19.6 %, respectively. The combined genotypic and phenotypic data indicate that ST-419 represents a novel species within the genus , for which the name sp. nov. is proposed. The type strain is ST-419 (=MCCC 1A17954=KCTC 25164).