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A novel marine hydrogen- and sulfur-oxidizing bacterium, designated strain S2-6  T , was isolated from the deep-sea sediment samples at the Longqi hydrothermal system, southwestern Indian Ocean. Cells were Gram-stain-negative, motile, short rods with a single polar flagellum. Growth was observed at 10-45 °C (optimum 33 °C), pH 5.0-8.0 (optimum pH 7.0) and 1.5 to 6.0% (w/v) NaCl with an optimum at 3.0% (w/v). The isolate was an obligate chemolithoautotroph capable of growth using thiosulfate, tetrathionate, elemental sulfur or sodium sulfide as the energy source, and oxygen or nitrate as the sole electron acceptor. When hydrogen was used as the energy source, strain S2-6  T could respire oxygen, nitrate or element sulfur. The major cellular fatty acids of strain S2-6  T were summed feature 3 (C 16:1 ω7c and/or C 16:1 ω6c), C 16:0 and summed feature 8 (C 18:1 ω7c and/or C 18:1 ω6c). The total size of its genome was 2,320,257 bp and the genomic DNA G + C content was 37.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences and core genes showed that the novel isolate belonged to the genus Sulfurimonas and was most closely related to Sulfurimonas paralvinellae GO25 T (96.8% sequence identity) and Sulfurimonas autotrophica OK10 T (95.8% sequence identity). The average nucleotide identity and DNA-DNA hybridization values between strain S2-6  T and S. paralvinellae GO25 T and S. autotrophica OK10 T were 74.6%-81.2% and 19.1%-24.6%, respectively. Based on the polyphase taxonomical data, strain S2-6  T represents a novel species of the genus Sulfurimonas, for which the name Sulfurimonas sediminis sp. nov. is proposed, with the type strain S2-6  T (= MCCC 1A14513 T  = KCTC 15854  T ).

A new mesophilic bacterium, designated strain 13-15A T , was isolated from the deep-sea water from the Carlsberg Ridge, northwestern Indian Ocean. Cells were short rods and motile with a single polar flagellum. Growth was observed in the presence of 85-1700 mM NaCl (optimum 680 mM), at 10-45 °C (optimum, 28 °C) and pH 5.0-9.0 (optimum, pH 7.0). The isolate was an obligate chemolithoautotroph capable of growth using thiosulfate, sulfide, elemental sulfur or tetrathionate as the sole energy source, carbon dioxide as the sole carbon source, and molecular oxygen as the sole electron acceptor. Molecular hydrogen did not support growth. The major fatty acids were C 16 : 1 (45.0 %), C 18 : 1 (22.5 %) and C 16 : 0 (20.1 %). The G+C content of the genomic DNA was 41.6 mol%. The results of phylogenetic analysis based on 16S rRNA gene sequences showed that the novel isolate belonged to the genus Thiomicrorhabdus and was most closely related to Thiomicrorhabdus hydrogeniphila MAS2 T (94.8 % sequence similarity). On the basis of the taxonomic data obtained in this study, strain 13-15A T represents a novel species of the genus Thiomicrorhabdus , for which the name Thiomicrorhabdus indica sp. nov. is proposed, with the type strain 13-15A T (=MCCC 1A13986 T =KCTC 15750 T ).