Regulation of nitrogenase synthesis by <i>Klebsiella pneumoniae</i>

Abstract

The synthesis of the nitrogenase system in N 2 -fixing bacteria is repressed when the organisms are grown on NH 4 + -N. It has not been unequivocally determined, however, if N 2 is necessary for induction in NH 4 + -deficient cultures. Previous experiments with Klebsiella pneumoniae, Azotobacter vinelandii, Clostridium pasteurianum, and Rhodospirillum rubrum have been inconclusive owing to inadequacy of the methods, primarily the presence of N 2 as a contaminant in the gases used. Results of experiments described in this paper using cultures of K. pneumoniae M5a1 grown under both limited N 2 and in its apparent absence indicate that the control of nitrogenase is most likely through simple repression by NH 4 + or by an incorporation product, e.g., glutamine.