Evidence from the structure and function of cytochromes c(2) that nonsulfur purple bacterial photosynthesis followed the evolution of oxygen respiration

Draft Genome Sequence and Brief History of Rhodovulum sp. Strain BSW8

Rhodovulum is a marine Gram-negative purple photosynthetic bacterial genus that is a member of the Alphaproteobacteria. Strain BSW8 is a variant that does not appear to make a polysaccharide slime capsule, and its genome sequence further contributes to the diversity of sequenced genomes belonging to this genus.

Rhodovulum is a marine Gram-negative purple photosynthetic bacterial genus that is a member of the Alphaproteobacteria. Strain BSW8 is a variant that does not appear to make a polysaccharide slime capsule, and its genome sequence further contributes to the diversity of sequenced genomes belonging to this genus.

Powered by light: Phototrophy and photosynthesis in prokaryotes and its evolution

Photosynthesis is a complex metabolic process enabling photosynthetic organisms to use solar energy for the reduction of carbon dioxide into biomass. This ancient pathway has revolutionized life on Earth. The most important event was the development of oxygenic photosynthesis. It had a tremendous impact on the Earth's geochemistry and the evolution of living beings, as the rise of atmospheric molecular oxygen enabled the development of a highly efficient aerobic metabolism, which later led to the evolution of complex multicellular organisms. The mechanism of photosynthesis has been the subject of intensive research and a great body of data has been accumulated. However, the evolution of this process is not fully understood, and the development of photosynthesis in prokaryota in particular remains an unresolved question. This review is devoted to the occurrence and main features of phototrophy and photosynthesis in prokaryotes. Hypotheses concerning the origin and spread of photosynthetic traits in bacteria are also discussed.

How the Reorganization Free Energy Affects the Reduction Potential of Structurally Homologous Cytochromes

Differences in the reduction potential E(0) among structurally similar metalloproteins cannot always be fully explained on the basis of their 3-D structures. We investigate the molecular determinants to E(0) using the mixed quantum mechanics/molecular mechanics approach named perturbed matrix method (PMM); after comparison with experimental values to assess the reliability of our calculations, we investigate the relationship between the change in free energy upon reduction ΔA(0) and the reorganization energy. We find that the reduction potential of cytochromes can be regarded as the result of the sum of two terms, one being mostly dependent on the energy fluctuations within a limited range around the mean transition energy and the second being mostly dependent linearly on the difference Δλ = λred - λox of the reorganization free energies for the ox → red (λred) and for the red → ox (λox) relaxations.

Photo-induced electron transfer in intact cells of Rubrivivax gelatinosus mutants deleted in the RC-bound tetraheme cytochrome: insight into evolution of photosynthetic electron transport

Deletion of two of the major electron carriers, the reaction center-bound tetrahemic cytochrome and the HiPIP, involved in the light-induced cyclic electron transfer pathway of the purple photosynthetic bacterium, Rubrivivax gelatinosus, significantly impairs its anaerobic photosynthetic growth. Analysis on the light-induced absorption changes of the intact cells of the mutants shows, however, a relatively efficient photo-induced cyclic electron transfer. For the single mutant lacking the reaction center-bound cytochrome, we present evidence that the electron carrier connecting the reaction center and the cytochrome bc(1) complex is the High Potential Iron-sulfur Protein. In the double mutant lacking both the reaction center-bound cytochrome and the High Potential Iron-sulfur Protein, this connection is achieved by the high potential cytochrome c(8). Under anaerobic conditions, the halftime of re-reduction of the photo-oxidized primary donor by these electron donors is 3 to 4 times faster than the back reaction between P(+) and the reduced primary quinone acceptor. This explains the photosynthetic growth of these two mutants. The results are discussed in terms of evolution of the type II RCs and their secondary electron donors.