Streicher S L, Shanmugam K T, Ausubel F, Morandi C, Goldberg R B
J Bacteriol. 1974 Nov;120(2):815-21. doi: 10.1128/jb.120.2.815-821.1974.
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 NH(4) (+). One strain, KP5069, produces 30% as much nitrogenase when grown in the presence of 15 mM NH(4) (+) 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.
通过P1介导的转导，将导致谷氨酰胺合成酶组成型合成（GlnC(-)表型）的突变从产气克雷伯菌转移到肺炎克雷伯菌中。肺炎克雷伯菌的此类GlnC(-)菌株具有谷氨酰胺合成酶的组成型水平。所研究的三株肺炎克雷伯菌GlnC(-)菌株中有两株，每株都含有独立分离的赋予GlnC(-)表型的突变，在有NH(4)(+)存在的情况下继续合成固氮酶。其中一株KP5069，在15 mM NH(4)(+)存在下生长时产生的固氮酶量是无NH(4)(+)时的30%。GlnC(-)表型使得在完全抑制野生型菌株中固氮酶合成的条件下仍能继续合成固氮酶。肺炎克雷伯菌的谷氨酰胺营养缺陷型，即不产生具有催化活性的谷氨酰胺合成酶的菌株，在氮限制生长期间无法合成固氮酶。用大肠杆菌附加体（F'133）对肺炎克雷伯菌Gln(-)菌株进行互补，可同时恢复谷氨酰胺合成酶活性和合成固氮酶的能力。这些结果表明谷氨酰胺合成酶在肺炎克雷伯菌的固氮过程中作为正调控元件发挥作用。
