Thiomicrospira thermophila sp. nov., a novel microaerobic, thermotolerant, sulfur-oxidizing chemolithomixotroph isolated from a deep-sea hydrothermal fumarole in the TOTO caldera, Mariana Arc, Western Pacific

1 Subground Animalcule Retrieval (SUGAR) Project, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka 237-0061, Japan 2 Department of Earth Sciences, University of Southern California, 3651 Trousdale Parkway, Los Angeles, CA 90089-0740, USA Correspondence Ken Takai kent{at}jamstec.go.jp A novel thermotolerant bacterium, designated strain I78 T , was isolated from a self-temperature-recording in situ colonization system deployed in a hydrothermal diffusing flow (maximal temperature 78 °C) at the TOTO caldera in the Mariana Arc, Western Pacific. Cells were highly motile curved rods with a single polar flagellum. Growth was observed at 15–55 °C (optimum 35–40 °C; 60 min doubling time) and pH 5·0–8·0 (optimum pH 6·0). The isolate was a microaerobic chemolithomixotroph capable of using thiosulfate, elemental sulfur or sulfide as the sole energy source, and molecular oxygen as the sole electron acceptor. The isolate was able to grow chemolithoautotrophically with carbon dioxide. Various organic substrates such as complex proteinaceous compounds, carbohydrates, organic acids, amino acids and sugars could also support growth as the carbon source instead of carbon dioxide with sulfur oxidation. The G+C content of the genomic DNA was 43·8 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the isolate belonged to the genus Thiomicrospira and was most closely related to Thiomicrospira crunogena strain TH-55 T and Thiomicrospira sp. strain L-12, while DNA–DNA hybridization demonstrated that the novel isolate could be genetically differentiated from previously described strains of Thiomicrospira . On the basis of its physiological and molecular properties the isolate is representative of a novel Thiomicrospira species, for which the name Thiomicrospira thermophila sp. nov. is proposed (type strain, I78 T =JCM 12397 T =DSM 16397 T ). Abbreviations: EPR, East Pacific Rise; STR-ISCS, self-temperature-recording in situ colonization Published online ahead of print on 2 July 2004 as DOI 10.1099/ijs.0.63284-0. The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of strain I78 T is AB166731 . The effects of temperature, pH and NaCl concentration on the growth of strain I78 T are shown in a supplementary figure available in IJSEM Online.