title: Identification of two new genes involved in diazotrophic growth via the alternative Fe-only nitrogenase in the phototrophic purple bacterium Rhodobacter capsulatus.
abstract: Growth of Rhodobacter capsulatus with molecular dinitrogen as the sole N source via the alternative Fe-only nitrogenase requires all seven gene products of the anfHDGK-1-2-3 operon. In contrast to mutant strains carrying lesions in the structural genes of nitrogenase (anfH, anfD, anfG, and anfK), strains defective for either anf1, anf2, or anf3 are still able to reduce the artificial substrate acetylene, although with diminished activity. To obtain further information on the role of Anf1, we screened an R. capsulatus genomic library designed for use in yeast two-hybrid studies with Anf1 as bait. Two genes, which we propose to call ranR and ranT (for genes related to alternative nitrogenase), coding for products that interact with Anf1 were identified. A ranR mutant exhibited a phenotype similar to that of an anf1 mutant strain (no growth with N2 in the absence of molybdenum, but significant reduction of acetylene via the Fe-only nitrogenase), whereas a ranT mutant retained the ability to grow diazotrophically, but growth was clearly delayed compared to the parental strain. In contrast to the situation for anf1, expression of neither ranR nor ranT was regulated by ammonium or molybdenum. A putative role for Anf1, RanR, and RanT in the acquisition and/or processing of iron in connection with the Fe-only nitrogenase system is discussed.
authors.affiliation: Ruhr-Universität Bochum, Fakultät für Biologie, Lehrstuhl für Biologie der Mikroorganismen, D-44780 Bochum, Germany.
authors.forename: Christa
authors.initials: C
authors.lastname: Sicking
authors.forename: Margit
authors.initials: M
authors.lastname: Brusch
authors.forename: Andreas
authors.initials: A
authors.lastname: Lindackers
authors.forename: Kai-Uwe
authors.initials: KU
authors.lastname: Riedel
authors.forename: Britta
authors.initials: B
authors.lastname: Schubert
authors.forename: Nazila
authors.initials: N
authors.lastname: Isakovic
authors.forename: Christiane
authors.initials: C
authors.lastname: Krall
authors.forename: Werner
authors.initials: W
authors.lastname: Klipp
authors.forename: Thomas
authors.initials: T
authors.lastname: Drepper
authors.forename: Klaus
authors.initials: K
authors.lastname: Schneider
authors.forename: Bernd
authors.initials: B
authors.lastname: Masepohl
mesh_terms: D005798:Genes, Bacterial / Q000502:physiology*; D008982:Molybdenum / Q000494:pharmacology; D009586:Nitrogen Fixation; D009591:Nitrogenase / Q000502:physiology*; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D016354:Rhodobacter capsulatus / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D000644:Quaternary Ammonium Compounds; D008982:Molybdenum; D009591:Nitrogenase