Growth kinetics and energetics of a deep-sea hyperthermophilic methanogen under varying environmental conditions

{A hyperthermophilic deep-sea methanogen, Methanocaldococcus strain JH146, was isolated from 26 degrees C hydrothermal fluid at Axial Volcano to model high temperature methanogenesis in the subseafloor. Emphasis was placed on defining growth kinetics, cell yields and growth energy demand (GE) across a range of conditions. The organism uses H-2 and CO2 as its sole carbon and energy sources. At various temperatures, pHs, and chlorinities, its growth rates and cell yields co-varied while GE remained uniform at 1.69x10(-11) J cell(-1)s(-1)+/- 0.68x10(-11) J cell(-1)s(-1) (s.d.