Isolation and characterization of Tn 5-induced NADPH-glutamate synthase (GOGAT-) mutants of Azorhizobium sesbaniae ORS571 and cloning of the corresponding glt locus

U. Hilgert, J. Schell, F. J. de Bruijn

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12 Scopus citations

Abstract

Random Tn 5 mutagenesis was used to isolate two independent Azorhizobium sesbaniae ORS571 mutants disturbed in ammonium assimilation (Asm-). Both Asm- mutant strains were shown to lack NADPH-glutamate synthase (NADPH-GOGAT) activity and to carry Tn 5 insertions ca. 1.5 kb apart in the ORS571 chromosome. The Tn 5-containing region of one of the GOGAT- mutant strains was cloned in pACYC184 and used to identify the wild-type glt (GOGAT) locus in a phage clone bank of ORS571. The cloned region was shown to have DNA homology with the Escherichia coli glt locus and to complement the Asm- phenotype of E. coli and ORS571 GOGAT- strains. The ORS571 GOGAT- mutations were found to interfere with free-living as well as symbiotic nitrogen fixation. Expression of ORS571 NADPH-GOGAT activity was shown to be independent of the nitrogen regulation (ntr) system.

Original languageEnglish (US)
Pages (from-to)195-202
Number of pages8
JournalMGG Molecular & General Genetics
Volume210
Issue number2
DOIs
StatePublished - Dec 1 1987

Keywords

  • Azorhizobium sesbaniae ORS571
  • Glutamate synthase
  • Nitrogen fixation/assimilation
  • Transposon Tn 5 mutagenesis

ASJC Scopus subject areas

  • Genetics

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