Pressure-Temperature Effects on Thermophilic Archaebacteria

The marine archaebacterium Methanococcus jannaschii was studied at high temperatures and hyperbaric pressures of helium to investigate the effect of pressure on the behavior of a deep-sea thermophile. Methanogenesis and growth at both 86C and 90C were accelerated by pressure up to 750 atm, but growth was not observed above 90C at either 7.8 atm or 250 atm. However, growth and methanogenesis were uncoupled above 90C, and the high-temperature limit for methanogensis was increased by pressure. Substantial methane formation was evident at 98C and 250 atm whereas no methane formation was observed at 94C and 7.8 atm. We have also constructed a novel bioreactor suitable for precise studies of enzymic reactions at elevated temperatures and pressures. Initial studies in this bioreactor at 86C indicate that the methyl viologen-reducing activity of hydrogenase in crude extracts of M. jannaschii is more than tripled by an increase in pressure from about 7.5 atm to 260 atm. Finally, we have purified a single hydrogenase from M. jannaschii 40-fold to apparent homogeneity. Keywords Archaebacteria Methanogens Hydrogenase Deep-sea hydrothermal vent Thermophiles.