Evidence for a regulatory link of nitrogen fixation and photosynthesis in Rhodobacter capsulatus via HvrA.
A Rhodobacter capsulatus reporter strain, carrying a constitutively expressed nifA gene and a nifH-lacZ gene fusion, was used for random transposon Tn5 mutagenesis to search for genes required for the NtrC-independent ammonium repression of NifA activity. A mutation in hvrA, which is known to be involved in low-light activation of the photosynthetic apparatus, released both ammonium and oxygen control of nifH expression in this reporter strain, demonstrating a regulatory link of nitrogen fixation and photosynthesis via HvrA. In addition, a significant increase in bacteriochlorophyll alpha (BChl alpha) content was found in cells under nitrogen-fixing conditions. HvrA was not involved in this up-regulation of BChl alpha. Instead, the presence of active nitrogenase seemed to be sufficient for this process, since no increase in BChl alpha content was observed in different nif mutants.
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Ruhr-Universität Bochum, Fakultät für Biologie, Lehrstuhl für Biologie der Mikroorganismen, Germany.
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Paschen
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Masepohl
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Klipp
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D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D005798:Genes, Bacterial; D009586:Nitrogen Fixation; D009591:Nitrogenase / Q000096:biosynthesis / Q000235:genetics; D010088:Oxidoreductases; D010100:Oxygen / Q000494:pharmacology; D010788:Photosynthesis; D010860:Pigments, Biological / Q000096:biosynthesis; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D016354:Rhodobacter capsulatus / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*
D001426:Bacterial Proteins; C090405:HvrA protein, Rhodobacter capsulatus; D010860:Pigments, Biological; D000644:Quaternary Ammonium Compounds; D015534:Trans-Activators; D010088:Oxidoreductases; D009591:Nitrogenase; C029130:nitrogenase reductase; D010100:Oxygen