Nitrogenase Synthesis in Klebsiella pneumoniae: Enhanced nif Expression without Accumulation of Guanosine 5'-Diphosphate 3'-Diphosphate

• Published in: Journal of general microbiology Vol. 130; no. 12; pp. 3063 - 3069
• Main Authors: Nair, Mrinalini B, Eady, Robert R
• Format: Journal Article
• Language: English
• Published: London Soc General Microbiol 01.12.1984; New York, NY Cambridge University Press
• Subjects: Adenosine Triphosphate - metabolism; Bacteriology; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation; Genes, Bacterial; Genetics; Glutamine - pharmacology; Guanine Nucleotides - metabolism; Guanosine Tetraphosphate - metabolism; Guanosine Triphosphate - metabolism; Klebsiella pneumoniae; Klebsiella pneumoniae - enzymology; Klebsiella pneumoniae - genetics; Microbiology; Nitrogen Fixation; Nitrogenase - biosynthesis; Transcription, Genetic; GTP; Enzyme; Biosynthesis; Gene expression; Regulation(control); Nitrogenase; Nitrogen fixation; Bacteria; Ratio; ATP; Klebsielleae; Klebsiella pneumoniae; Enterobacteriaceae; Glutamine
• ISSN: 0022-1287; 1350-0872; 1465-2080
• DOI: 10.1099/00221287-130-12-3063

AFRC Unit of Nitrogen Fixation, University of Sussex, Brighton BN1 9RQ, UK ABSTRACT Summary: Derepression of nitrogen fixation ( nif ) genes in Klebsiella pneumoniae following transfer from NH + 4 -sufficiency to N-free medium was preceded rapid expansion of the guanosine 5'-di-phosphate 3'-diphosphate (ppGpp) pool. When derepressed in N-free medium supplemented with glutamine (600 µg ml –1 ), expression from the nif H and nif L promoters, determined as β-galactosidase activity in nif : : lac merodiploid strains, was stimulated 7-fold and nitrogenase activity 26-fold; ppGpp did not accumulate, remaining at the levels found in NH + 4 -repressed populations. The relaxed mutant K. pneumoniae relA40 , which accumulates only very low levels of ppGpp, showed partial derepression of nitrogenase activity in the presence of glutamine, thus ppGpp is unlikely to be an effector of nif expression. ATP and GTP levels were elevated under conditions where nif expression was enhanced, consistent with previous data suggesting that maintenance of ATP levels is a prerequisite for the expression of nif genes in K. pneumoniae.