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 la titude of 21 degrees N. This strain is a strictly anaerobic coccus, an d its cells range from 0.8 to 2 mu m in diameter. The optimum temperat ure, pH, and Sea Salt concentration for growth are 85 degrees C, 6, an d 20 to 40 g/liter, respectively, Strain AL662(T) grows preferentially on proteolysis products, on a mixture of 20 amino acids, and on malto se 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 t o the genus Thermococcus. On the basis of hybridization results, we pr opose that this strain should be placed in a new species, Thermococcus hydrothermalis.