FIG. 4.

Effects of the shift in growth conditions from anaerobic-light to aerobic-dark on the levels of spectral complexes. (A) Growth profile of R. sphaeroides 2.4.1. After the strain was grown anaerobically by sparging it with 95% N₂-5% CO₂ in the light (10 W/m²) to an OD₆₀₀ of 0.086, the growth conditions were shifted to aerobic-dark by sparging with 69% N₂-30% O₂-1% CO₂. The time point when the growth conditions were shifted is indicated by an arrow and a number zero. The numbers one to four indicate the first, second, third, and fourth culture-doubling times after the shift, respectively. (B) Absorption spectra of crude cell extracts obtained from the cells during the transition from photosynthesis to aerobic respiration. Samples were prepared just before the shift (0) and at each doubling time (1 to 4) after the shift. Equal protein concentrations (0.17 μg/ml) were used for the measurement.