Thermococcus thioreducens sp. nov., a novel hyperthermophilic, obligately sulfur-reducing archaeon from a deep-sea hydrothermal vent

1 Astrobiology Laboratory, NASA/NSSTC, VP62, 320 Sparkman Dr., Huntsville, AL 35805, USA 2 Laboratory for Structural Biology, Department of Biological Sciences, The University of Alabama in Huntsville, MSB 221, Huntsville, AL 35899, USA 3 Japan Collection of Microorganisms, RIKEN BioResource Center, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan 4 Department of Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA 5 United States Department of Agriculture, Monitoring Programs Office, 8609 Sudley Rd., Suite 206, Manassas, VA 20110, USA 6 Department of Microbiology, University of Georgia, Athens, GA 30602-2605, USA 7 Department of Biological Sciences, UAH, Huntsville, AL 35899, USA Correspondence Elena V. Pikuta elenapikuta{at}hotmail.com A hyperthermophilic, sulfur-reducing, organo-heterotrophic archaeon, strain OGL-20P T , was isolated from ‘black smoker’ chimney material from the Rainbow hydrothermal vent site on the Mid-Atlantic Ridge (36.2°N, 33.9°W). The cells of strain OGL-20P T have an irregular coccoid shape and are motile with a single flagellum. Growth was observed within a pH range of 5.0–8.5 (optimum pH 7.0), an NaCl concentration range of 1–5 % (w/v) (optimum 3 %) and a temperature range of 55–94 °C (optimum 83–85 °C). The novel isolate is strictly anaerobic and obligately dependent upon elemental sulfur as an electron acceptor, but it does not reduce sulfate, sulfite, thiosulfate, Fe(III) or nitrate. Proteolysis products (peptone, bacto-tryptone, Casamino acids and yeast extract) are utilized as substrates during sulfur reduction. Strain OGL-20P T is resistant to ampicillin, chloramphenicol, kanamycin and gentamicin, but sensitive to tetracycline and rifampicin. The G+C content of the DNA is 52.9 mol%. The 16S rRNA gene sequence analysis revealed that strain OGL-20P T is closely related to Thermococcus coalescens and related species, but no significant homology by DNA–DNA hybridization was observed between those species and the new isolate. On the basis of physiological and molecular properties of the new isolate, we conclude that strain OGL-20P T represents a new separate species within the genus Thermococcus , for which we propose the name Thermococcus thioreducens sp. nov. The type strain is OGL-20P T (=JCM 12859 T =DSM 14981 T =ATCC BAA-394 T ). Abbreviations: TEM, transmission electron microscopy The GenBank accession number for the 16S rRNA gene sequence of strain OGL-20P T is AF394925 .