Aerobiosis and the hemoprotein content of photosynthetic bacteria

Summary

Rhodospirillum rubrum and Rhodopseudomonas spheroides, grown under various degrees of illumination, aeration, and iron deprivation, have been assayed for their content of cytochrome c, RHP, catalase, total iron, bacteriochlorophyll, and carotenoids.

Concentrations of bacteriochlorophyll and carotenoids were consistent with the findings of Cohen-Bazire et al. (1957).

Total iron content, which ranged from 0.017 to 0.04% of the dry weight, reflected the content of the principal hemoproteins but exceeded the amount of iron in these hemoproteins.

The catalase content of R. rubrum, on a dry weight basis, was 0.0005% for cells grown anaerobically in the light, and 0.0028% for cells grown in darkness with vigorous aeration; that of Rps. spheroides was 0.006% and 0.25%, respectively. The catalase content in both species rose with increasingly vigorous aeration.

Cytochrome c in both species, and RHP in R. rubrum, attained the same levels in cells grown under vigorous aeration as in cells grown anaerobically in the light. In cells grown under limited aeration the levels of these substances were about 50% higher. In Rps. spheroides the RHP content was greatest in cells grown anaerobically, falling under gentle aeration and declining further under more vigorous aeration.

Iron deficiency caused a decrease in the catalase content of cells grown anaerobically in the light but not in cells grown aerobically. The content of cytochrome c and of RHP was diminished by iron depletion in aerobic cultures, but not in anaerobic cultures.