Oxidation-reduction potential dependence of the interaction of cytochromes, bacteriochlorophyll and carotenoids at 77 degrees K in chromatophores of Chromatium D and Rhodopseudomonas gelatinosa.

The Evolution of Photosynthesis

1 – Introduction to Photosynthesis

In mesophyll chloroplasts from maize, photosystem (PS) II activities (2,6 dichlorophenol indophenol photoreduction and the variable fluorescence yield of chlorophyll (Chl) a) are inhibited strongly by 0.5 mM cadmium, supplied as Cd(NO3)2. However, diphenylcarbazide restores these activities suggesting that cadmium inhibits PSII activity at the oxygen evolving site between water and Y (the first secondary electron donor of PSII). PSI activity (light induced P700 oxidation) is insensitive' to cadmium. Furthermore, absorption and fluorescence studies showed that cadmium causes a 20% to 30% decrease in the total chlorophylls, 15% to 25% decrease in the ratio of Ch1 a/Chl b and a 20% to 25% decrease in the ratio of the short to the long wavelength forms of Chl a.

Effects of cadmium nitrate on spectral characteristics and light reactions of chloroplasts.

Publisher Summary Bacterial and green-plant photosynthesis share a number of basic features, but are distinctly different in respect to one another. The physiological property of the photosynthetic bacteria that makes the bacteria unique in the biological world states the ability of bacteria to grow rapidly under anaerobic conditions, using light as the ultimate energy source. The photosynthetic bacteria display a remarkable metabolic diversity and versatility. Essentially, in the anabolic phase of cell growth, appropriate organic intermediates and monomers are produced from the carbon and nitrogen sources of the external medium and these are utilized for the synthesis of proteins, nucleic acids, lipids, carbohydrates, and various other complex cellular substances. Synthesis of the intermediates and monomers requires energy in the form of ATP and reducing power—primarily as reduced nicotinamide nucleotide. The chapter describes photophosphorylation, generation of net reducing power, comparison of energy metabolism and electron-transfer patterns in photosynthetic bacteria and clostridia, and the regulatory mechanisms.

Charles F. Fowler

Papers

Evidence for two light-driven reactions in the purple photosynthetic bacterium, Rhodospirillum rubrum.

Light- and chemically-induced oxidation-reduction reactions in chromatophore fractions of Rhodospirillum rubrum.