Effect of diquat (1,1'-ethylene-2,2'-dipyridylium dibromide) on the photosynthetic growth of Rhodospirillum rubrum.

Diquat (2 x 10(-4)m) inhibited both aerobic and anaerobic growth of Rhodospirillum rubrum. With photosynthetic cultures, diquat affected the synthesis of bacteriochlorophyll more readily than cell mass (turbidity). Diquat retarded the synthesis of bacteriochlorophyll and some protein more readily than that of other cellular constituents such as ribonucleic acid, deoxyribonucleic acid, and cell mass. With cells deficient in phosphate, diquat inhibited the uptake-conversion of inorganic phosphate completely only when 3-(3,4-dichlorophenyl)-1,1'-dimethyl urea and ascorbate were also present.