Thermococcus prieurii sp nov., a hyperthermophilic archaeon isolated from a deep-sea hydrothermal vent

A novel hyperthermophilic, anaerobic archaeon, strain Bio-pl-0405IT2(T), was isolated from a hydrothermal chimney sample collected from the East Pacific Rise at 2700 m depth in the 'Sarah Spring' area (7 degrees 25' 24 '' S 107 degrees 47' 66 '' W). Cells were irregular, motile cocci (0.8-1.5 mu m in diameter) and divided by constriction. Growth was observed at temperatures between 60 degrees C and 95 degrees C with an optimum at 80 degrees C. The pH range for growth was between pH 4.0 and pH 8.0 with an optimum around pH 7.0. Strain Bio-pl-0405IT2(T) grew at salt concentrations of 1-5 % (w/v) NaCl with an optimum at 2 %. The novel isolate grew by fermentation or sulphur respiration on a variety of organic compounds. It was a chemoorganoheterotrophic archaeon growing preferentially with yeast extract, peptone and tryptone as carbon and energy sources and sulphur and organic compounds as electron acceptors; it also grew on maltose and starch. Sulphur or L-cystine were required for growth and were reduced to hydrogen sulfide. The strain was resistant to rifampicin, chloramphenicol, vancomycin and kanamycin (all at 100 mu g ml(-1)) but was sensitive to tetracycline. The G+C content of its genomic DNA was 53.6 mol%. Phylogenetic analysis of the almost complete 16S rRNA gene sequence (1450 bp) of strain Bio-pl-0405IT2(T) showed that the novel isolate belonged to the genus Thermococcus. DNA-DNA hybridization values with the two closest relatives Thermococcus hydrothermalis AL662(T) and Thermococcus celer JCM 8558(T) were below the threshold value of 70%. On the basis of the physiological and genotypic distinctness, we propose a novel species, Thermococcus prieurii sp. nov. The type strain is Bio-pl-0405IT2(T) (=CSUR P577(T)=JCM 16307(T)).