Pressure and Temperature Effects on Growth and Methane Production of the Extreme Thermophile Methanococcus jannaschii.

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 (as measured by protein production) at both 86 and 90 degrees C were accelerated by pressure up to 750 atm (1 atm = 101.29kPa), but growth was not observed above 90 degrees C at either 7.8 or 250 atm. However, growth and methanogenesis were uncoupled above 90 degrees C, and the high-temperature limit for methanogenesis was increased by pressure. Substantial methane formation was evident at 98 degrees C and 250 atm, whereas no methane formation was observed at 94 degrees C and 7.8 atm. In contrast, when argon was substituted for helium as the pressurizing gas at 250 atm, no methane was produced at 86 degrees C. Methanogenesis was also suppressed at 86 degrees C and 250 atm when the culture was pressurized with a 4:1 mix of H(2) and CO(2), although limited methanogenesis did occur when the culture was pressurized with H(2).