Effect of O₂ concentrations on Sulfolobus solfataricus P2

Sulfolobus solfataricus P2 was grown aerobically at various O₂ concentrations. Based on growth parameters in microcosms, four types of behavior could be distinguished. At 35% O₂ (v/v; gas phase), the cultures did not grow, indicating a lethal dose of oxygen. For 26-32% O₂, the growth was significantly affected compared with the reference (21%), suggesting a moderate toxicity by O₂. For 16-24% O₂, standard growth was observed. For 1.5-15% O₂, growth was comparable with the reference, but the yield on O₂ indicated a more efficient use of oxygen. These results indicate that S. solfataricus P2 grows optimally in the range of 1.5-24% O₂, most likely by adjusting its energy-transducing machinery. To gain some insight into control of the respiratory system, transcriptomes of the strain cultivated at different O₂ concentrations, corresponding to each behavior (1.5%, 21% and 26%), were compared using a DNA microarray approach. It showed differential expression of several genes encoding terminal oxidases, indicating an adaptation of the strain's respiratory system in response to fluctuating oxygen concentrations.