Regulation of Nitrogen Fixation in Klebsiella pneumoniae: Evidence for a Role of Glutamine Synthetase as a Regulator of Nitrogenase Synthesis
AUTOR(ES)
Streicher, Stanley L.
RESUMO
Mutations causing constitutive synthesis of glutamine synthetase (GlnC− phenotype) were transferred from Klebsiella aerogenes into Klebsiella pneumoniae by P1-mediated transduction. Such GlnC− strains of K. pneumoniae have constitutive levels of glutamine synthetase. Two of three GlnC− strains of K. pneumoniae studied, each containing independently isolated mutations that confer the GlnC− phenotype, continue to synthesize nitrogenase in the presence of NH4+. One strain, KP5069, produces 30% as much nitrogenase when grown in the presence of 15 mM NH4+ as in its absence. The GlnC− phenotype allows the synthesis of nitrogenase to continue under conditions that completely repress nitrogenase synthesis in the wild-type strain. Glutamine auxotrophs of K. pneumoniae, that do not produce catalytically active glutamine synthetase, are unable to synthesize nitrogenase during nitrogen limited growth. Complementation of K. pneumoniae Gln− strains by an Escherichia coli episome (F′133) simultaneously restores glutamine synthetase activity and the ability to synthesize nitrogenase. These results indicate a role for glutamine synthetase as a positive control element for nitrogen fixation in K. pneumoniae.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=245843Documentos Relacionados
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