Reversibility of oxygen induced inactivation of nitrogenase in some enterobacteria

Aerobic and microaerobic diazotrophs possess numerous oxygen restriction strategies to protect nitrogenase from inactivation by oxygen without interfering with energy generation through oxidative phosphorylation. Protection by conformational change in nitrogenase was first detected and described in Azotobacter. This strategy once considerd unique for Azotobacter has been shown in this study to occur in Citrobacterfreundii (Braak) Werkman and Gillen and Klebsiella pneumoniae subspecies rhinoscleromatis (Trevisan) Migula also. However, in these enteric bacteria the entire enzyme is not protected probably due to the absence of any respiratory protection similar to that found in the aerobe, Azotobacter.