STETTERIA HYDROGENOPHILA, GEN. NOV. AND SP. NOV., A NOVEL MIXOTROPHICSULFUR-DEPENDENT CRENARCHAEOTE ISOLATED FROM MILOS, GREECE

A new hyperthermophilic, strictly anaerobic crenarchaeote, Stetteria h ydrogenophila DSM11227 representing a new genus within the family of D esulfurococcaceae, was isolated from the sediment of a marine hydrothe rmal system at Paleohori Bay in Miles, Greece. Cells are gram-negative irregular and disc-shaped cocci, 0.5-1.5 mu m in diameter, which are flagellate and can form cytoplasmatic protrusions up to 2 mu m in leng th. The strain grew optimally at 95 degrees C at pH 6.0 and at a NaCl concentration of 3%. The organism grew mixotrophically on peptide subs trates. It required elemental sulfur as an external electron acceptor, and in addition, its.growth was completely dependent on the presence of molecular hydrogen. Sulfur could be replaced by thiosulfate. H2S, C O2, acetate, and ethanol were identified as products of metabolism. Th e G + C content of DNA was 65 mol%. Analysis of its phylogenetic posit ion by sequence analysis of 16S rRNA placed this organism in the famil y of Desulfurococcaceae. The dependence of this organism on both hydro gen and sulfur during growth on peptide substrates distinguishes Stett eria from all previously described species of Crenarchaeota.