Thermococcus waiotapuensis sp nov., an extremely thermophilic archaeon isolated from a freshwater hot spring

An extremely thermophilic, sulfur-dependent archaeon, strain WT1, was isola ted from a freshwater hot spring in the Lake Taupo area of North Island, Ne w Zealand. The cells are flagellated, strictly anaerobic cocci that grow op timally at 85 degrees C and 5.4 g NaCl l(-1). The strain grows heterotrophi cally on complex proteinaceous substrates or on appropriate salts plus amin o acid mixtures and is also able to utilize maltose, starch, and pyruvate. Elemental sulfur could be replaced by cystine or thioglycollate. The range of temperatures allowing growth is from 60 to 90 degrees C; the pH supporti ng growth ranges from 5 to 8 (optimum, pH 7). Strain WT1 grew in a defined medium containing amino acids as the sole carbon and energy sources. The re quired amino acids were: Arg, His, Ile, Leu, Phe, Ser, Thr, Trp, Tyr, and V al. Strain WT1 showed sensitivity to rifampicin. DNA G+C content was 50.4 m ol%. Phylogenetic analysis of the sequence encoding the 16S rRNA gene indic ated that this isolate is a member of the Thermococcales. DNA/DNA hybridiza tion studies revealed no similarity to several species of Thermococcus and Pyrococcus, with the exception of Thermococcus zilligii. Based on the repor ted results, we propose strain WT1 as a new species to be named Thermococcu s waiotapuensis sp. nov.