Pyruvate fermentation in light-grown cells ofRhodospirillum rubrum during adaptation to anaerobic dark conditions

Pyruvate fermentation inRhodospirillum rubrum (strains F₁, S₁, and Ha) was investigated using cells precultured on different substrates anaerobically in the light and than transferred to anaerobic dark conditions. Pyruvate formate lyase was always the key enzyme in pyruvate fermentation but its activity was lower than in cells which have been precultured aerobically in darkness. The preculture substrate also had a clear influence on the pyruvate formate lyase activity. Strains F₁ and S₁ metabolized the produced formate further to H₂ and CO₂. A slight production of CO₂ from pyruvate, without additional H₂-production, could also be detected. It was concluded from this that under anaerobic dark conditions a pyruvate dehydrogenase was also functioning. On inhibition of pyruvate formate lyase the main part of pyruvate breakdown was taken over by pyruvate dehydrogenase.When enzyme synthesis was inhibited by chloramphenicol, propionate production in contrast to formate production was not affected. Protein synthesis was not significant during anaerobic dark culture. Bacteriochlorophyll. however, showed, after a lag phase, a clear rise.Abbreviations Bchl Bacteriochlorophyll - CoA Coenzyme A - DSM Deutsche Sammlung von Mikroorganismen (Göttingen) - OD optical density - PHBA poly--hydroxybutyric acid - R Rhodospirillum