Thermococcus hydrothermalis sp. nov, a new hyperthermophilic Archaeon isolated from a deep-sea hydrothermal vent

An extremely thermophilic archaeon, strain AL662(T), was isolated from a deep-sea hydrothermal vent located on the East Pacific Rise at a latitude of 21 degrees N. This strain is a strictly anaerobic coccus, and its cells range from 0.8 to 2 mu m in diameter. The optimum temperature, pH, and Sea Salt concentration for growth are 85 degrees C, 6, and 20 to 40 g/liter, respectively, Strain AL662(T) grows preferentially on proteolysis products, on a mixture of 20 amino acids, and on maltose in the presence of elemental sulfur. The membrane lipids consist of di- and tetraether glycerol lipids, The DNA G + C content is 58 mol%. Sequencing of the 16S rRNA gene showed that strain AL662(T) belongs to the genus Thermococcus. On the basis of hybridization results, we propose that this strain should be placed in a new species, Thermococcus hydrothermalis.