Oxidative stress, caused by increased levels of superoxide anion (O2-*), hydrogen peroxide (H2O2), or the hydroxyl radical (OH *), can lead to damage in all cellular components. Several enzymes are responsible for removing these reactive species from the cell, and are activated in response to oxidative stress and to other that trigger this situation, such as high concentrations of iron. The enzyme catalase-peroxidase (KatG) and the two subunits of alkyl hydroperoxide reductase (AhpC and AhpF) protect against the toxic effects of peroxides through the direct elimination of oxidants. The superoxide dismutases (SOD) are important in the removal of superoxide ions. This work aims at defining the regulatory mechanisms of gene expression of the ahpCF, sodA, sodB, and genes from sodC C. crescentus. For this, the levels of transcription and translation of these genes will be evaluated in wild type and mutant strains for oxyR, fur, sigF and sigE, as these genes were previously described as involved in regulating the response to oxidative stress. Transcriptional and translational fusions to the lacZ reporter gene will be constructed, to determine if the regulation occurs at transcriptional or post-transcriptional levels. The regulatory regions of these genes will be determined by mapping the binding site of proteins to promoters.
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