LIGHT-DEPENDENT AND LIGHT-INDEPENDENT PRODUCTION OF HYDROGEN GAS BY PHOTOSYNTHESIZING RHODOSPIRILLUM RUBRUM MUTANT C

Autor: T. E. Gorrell, R. L. Uffen
Rok vydání: 1978
Předmět:
Zdroj: Photochemistry and Photobiology. 27:351-358
ISSN: 1751-1097
0031-8655
DOI: 10.1111/j.1751-1097.1978.tb07611.x
Popis: Rhodospirillum rubrum mutant C grew photosynthetically in the light and produced copious amounts of H2. During light-growth mutant C produced 7.9mmol of H2 in medium with 9mmol of Na-pyruvate per mg protein. When parent strain R. rubrum S1 was grown similarly, these cells only produced a trace amount of H2. Light-grown mutant C evolved H2 by H2-nitrogenase and formic hydrogenlyase. Although both hydrogenases were previously detected in R. rubrum S1, the activities of the reactions in light-grown mutant C were higher and they operated under different conditions. In the parent strain S1, the production of nitrogenase was strongly repressed during growth in medium enriched with organic nitrogen and the cells only reduced 0.06 pmol of acetylene per mg protein after 30 min in the light. Under similar conditions, nitrogenase activity measured by the acetylene reduction test in mutant C was 10-fold greater. In addition to nitrogenase, mutant C also produced large amounts of H2 with formate as an intermediate when the cells were grown with Na-pyruvate. Formic hydrogenlyase in mutant C operated equally well in anaerobic light or dark conditions. The analogous formate oxidation reaction in parent strain S1 only functioned in the dark. These data, compared with results with R. rubrum S1 suggested that C was a regulatory mutant. Additional observations suggested that formic hydrogenlyase occurred constitutively in R. rubrum. Pyruvate formate-lyase, however, which produced formate for formic hydrogenlyase, was only detected in the cells after growth in media with Na-pyruvate. The reaction was not formed when R. rubrum was grown in the light in media with dl-malate as the sole carbon substrate.
Databáze: OpenAIRE
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