title: Evidence for a regulatory link of nitrogen fixation and photosynthesis in Rhodobacter capsulatus via HvrA.
abstract: 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.
authors.affiliation: Ruhr-Universität Bochum, Fakultät für Biologie, Lehrstuhl für Biologie der Mikroorganismen, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Kern
authors.forename: P B
authors.initials: PB
authors.lastname: Kamp
authors.forename: A
authors.initials: A
authors.lastname: Paschen
authors.forename: B
authors.initials: B
authors.lastname: Masepohl
authors.forename: W
authors.initials: W
authors.lastname: Klipp
mesh_terms: 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*
chemical_list: 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