THERMOCOCCUS ALCALIPHILUS SP-NOV, A NEW HYPERTHERMOPHILIC ARCHAEUM GROWING ON POLYSULFIDE AT ALKALINE PH

A novel coccoid-shaped, hyperthermophilic, heterotrophic member of the archaea was isolated from a shallow marine hydrothermal system at Vul cano Island, Italy, The isolate grew between 56 and 90 degrees C with an optimum around 85 degrees C. The pH range fur growth was 6.5 to 10. 5, with an optimum around 9.0. Polysulfide and elemental sulfur were r educed to H2S. Sulfur stimulated the growth rate. The isolate fermente d yeast extract, peptone, meat extract, tryptone, and casein, Isovaler ate, isobutyrate, propionate, acetate, CO2, NH3, and H2S (in the prese nce of S degrees) were detected as end products. Growth was not inhibi ted by H-2. Based on DNA-DNA hybridization and 16S rRNA partial sequen ces, the new isolate represents a new species of Thermococcus, which w e named Thermococcus alcaliphilus. The type strain is isolate AEDII12 (DSM 10322).