Details for Pyrolobus

Pyrolobus is an interesting example of a prokaryote whose growth temperature optimum lies at or even above 100°C; the optimum being 106°C. Pyrolobus fumarrii currently holds the record for the most thermophilic of all known organisms - its growth temperature maximum is 113°C (notably, P. fumarrii is unable to grow below 90°C because it is too cold!). Pyrolobus lives in the wall s of "black smoker" hydrothermal vent chimneys where, because of its autotrophic abilities, it is possibly a major source of primary productivity in this otherwise inorganic environment. Pyrolobus cells are coccoid-shaped and the cell wall is composed of protein. The organism is an obligate H₂ chemolithotroph, growing at the expense of H₂ oxidation coupled to the reduction of NO₃^- (to NH₄⁺), S₂O₃^2- (to H₂S), or very low concentrations of O₂ (to H₂O). Besides its extremely thermophilic nature, Pyrolobus is also resistant to termperatures substantially above its growth temperature maximum. For example, cultures of P. fumarrii survive autoclaving (121°C) for 1 h, a condition that even bacterial endospores cannot withstand. Considering the hydrothermal vent habitat of this organism, where periodic shifts in the temperature may be a regular occurrence, high heat resistance would be of great survival value.