Isolation and characterization of hyperthermophilic archaebacteria from Southwestern Pacific hydrothermal vents

Abstract

Two hyperthermophllic Archaea. strains OG-1 and SM-2, were isolated from new deep -sea hydrothermal vent areas in the Southwestern Pacific Ocean. These strains were coed. oWifiaUly anaerobic archaea of abou 10.7-2wm diafneter. Optimum growth conditions to 00-1 and SM-2 were at a temperature of 85-90^2 (range SO-iWC), pK of 6 (range 4-8), NaCI concentration of Z% (range 1-5%), and a nutrient concentration (tryptone + yeast extract) of 0.2% (range 0.005-5%). Elemental sulfur stimulated growth by a factor of about 4. Ammonium slightly stimulated growth. Both tryptone and yeast extract allowed growth as sole carbon sources ; and these isolates were neither able to utilise nor growth exclusively on glucose, maltose, succinate, propionate, acetate, or an amino acid mixture. DNA GC content was 52 mol%. Sequencing of a fragment of the 16S rDNA gene indicated that these isolates belonged to Lhe genus Thermococcus. OG-1 and SM-2 showed differential characteristics with those of the already described spccies of Thermococcus. OG-1 and SM-2 showed the fastest growth rate within the genus Thermococcus. OG-1 and SM-2 cell envelopes also revealed differences with other Thermococcus strains. Genetic analysis showed that the species of Thermococcus were more closely related between them than with our isolate