AMMONIA-EXCRETING MUTANTS OF KLEBSIELLA-PNEUMONIAE WITH A PLEIOTROPICDEFECT IN NITROGEN-METABOLISM

Enterobacterial mutants defective in the nitrogen control regulatory s ystem (Ntr) generally display a pleiotropic phenotype with regard to e xpression and regulation of several enzymes and transport systems invo lved in the assimilation of N sources. This report describes the isola tion and characterization of similar pleiotropic mutants of Klebsiella pneumoniae that cannot be complemented by ntt. genes, The strains exc reted ammonia, were unable to grow on a number of N sources, and conta ined low glutamine:2-oxoglutarate amino transferase and normal, but un modifiable glutamine synthetase activities and a nitrogenase level lar gely unaffected by ammonium, but still repressible by an amino acid mi xture, Genetic studies suggested that this phenotype is due to overexp ression of an unknown regulatory protein.