Effect of diquat (1,1′-ethylene-2,2′-dpyridylium dibromide) on the formation and photoreactions of chromatophores from Rhodospirillum rubrum

Analysis of chromatophore suspensions fractionated from Rhodospirillum rubrum indicated that the diphenylamine did not interfere with the cellular synthesis of bacteriochloropyll (absorption at 775 mμ in acetone-methanol). Diquat, on the other hand, interfered with the synthesis of both bacteriochlorophyll within chromatophore suspensions and the detectable Rhodospirillum heme protein of the supernatant (absorption at 435 mμ). While photoreduction of O₂ was dependent on substrates such as malate or succinate, photophosphorylation by chromatophore suspensions was mostly independent of these substrates under aerobic conditions. Under anaerobic conditions, ascorbate plus 2,6-dichlorophenolindophenol caused an “ovver-reduced” environment in which photophosphorylation was inhibited but was restored by diquat. The photophosphorylation altered by reduced 2,6-dichlorophenolindophenol and phenazine methosulfate seemed to be related to the presence of atmospheric O₂; the stimulation by phenazine methosulfate was dependent on both siccinate and O₂;