Mutation of cytochrome bd quinol oxidase results in reduced stationary phase survival, iron deprivation, metal toxicity and oxidative stress in Azotobacter vinelandii
Se. Edwards et al., Mutation of cytochrome bd quinol oxidase results in reduced stationary phase survival, iron deprivation, metal toxicity and oxidative stress in Azotobacter vinelandii, FEMS MICROB, 185(1), 2000, pp. 71-77
Azotobacter vinelandii cydAB mutants lacking cytochrome bd lost viability i
n stationary phase, irrespective of temperature, but microaerobiosis or iro
n addition to stationary phase cultures prevented viability loss. Growth on
solid medium was inhibited by a diffusible factor From neighbouring cells,
and by iron chelators, In(III) or Ca(III); microaerobic growth overcame in
hibition by the extracellular factor. Siderophore production and total Fe(I
II)-chelating activity were not markedly affected in Cyd(-) mutants, and re
mained responsive to iron repression. Cyd- mutants were hypersensitive to C
u(II), Zn(II), and compounds exerting oxidative stress. Failure to synthesi
se haemoproteins does not explain the complex phenotype since mutants retai
ned significant catalase activity. We hypothesise that Cyd(-) mutants are d
efective in maintaining the near-anoxic cytoplasm required for reductive ir
on metabolism and nitrogenase activity. (C) 2000 Federation of European Mic
robiological Societies. Published by Elsevier Science B.V. All rights reser
ved.