title: Influence of low oxygen concentration on derepression of nitrogenase in Klebsiella pneumoniae.
abstract: Effects of oxygen derepression of nitrogenase were studied in Klebsiella pneumoniae, using oxyleghaemoglobin to supply and monitor very low dissolved O2 concentrations in a steady-state system. Expression of the nifH gene was studied by using a nifH::lac fusion strain, which aslo carried the Nif+ plasmid pRD1 so that the production of active nitrogenase could also be monitored. When compared with anaerobic treatments, very low concentrations of dissolved O2 inhibited derepression of both nifH::lac and pRD1 nif. Fifty percent inhibition of derepression occurred at 0.1 microM-O2. The apparent Ks of the dominant terminal oxidase was 0.08 microM-O2. These results suggest that there is a close relationship between the terminal respiratory system of these bacteria and the repression of nitrogenase by O2.
mesh_terms: D004794:Enzyme Repression / Q000187:drug effects*; D005796:Genes; D005798:Genes, Bacterial; D007711:Klebsiella pneumoniae / Q000201:enzymology* / Q000235:genetics; D007874:Leghemoglobin / Q000378:metabolism; D009591:Nitrogenase / Q000378:metabolism*; D010100:Oxygen / Q000494:pharmacology*; D010957:Plasmids
chemical_list: D007874:Leghemoglobin; D009591:Nitrogenase; D010100:Oxygen