EFFECT OF OXYGEN ON GROWTH AND THE SYNTHESIS OF BACTERIOCHLOROPHYLL IN RHODOSPIRILLUM MOLISCHIANUM.

Sistrom, W. R. (University of Oregon, Eugene). Effect of oxygen on growth and the synthesis of bacteriochlorophyll in Rhodospirillum molischianum. J. Bacteriol. 89:403-408. 1965.-The basis of the strict anaerobiosis of the nonsulfur purple bacterium Rhodospirillum molischianum was investigated. The bacterium is unable to grow aerobically in the dark. In the light, the only immediate effect of oxygen is to inhibit the biosynthesis of bacteriochlorophyll and carotenoid pigments. Growth and protein synthesis are not inhibited directly, nor are the cells killed by oxygen. The inhibition of bacteriochlorophyll synthesis ultimately leads to inhibition of growth. Oxygen inhibits photopigment synthesis by means of a metabolic control system which is apparently identical with the one already known in facultatively aerobic species such as R. rubrum. Whole cells of R. molischianum respire in the dark; illumination inhibits respiration by about 50%. Cell-free extracts display significant levels of dark reduced nicotinamide adenine dinucleotide oxidase activity. Both these properties are in accord with the physiological behavior of the organism.