Fig. 4.

Exposure of P. furiosus cultures to O₂ decreases H₂ production in a linear fashion. Cultures (40 mL) in 100-mL bottles were grown at 95 °C in medium containing 5 g/L maltose, 0.5 g/L yeast extract but no added sulfide on a shaking platform (150 rpm). After 6 h of growth, cultures were exposed to a range of O₂ concentrations (0.8–4.9 mM in the gas phase) and the amount of H₂ produced was measured at 0 (circles), 2 (squares), 4 (triangles), and 6 h (diamonds) after O₂ exposure.