Bacteria have to deal with the paradox emerged from metal requirements and its toxicity when in excess. The most common mechanism used is the regulation of genes involved in uptake, storage and efflux of metals. In zinc homeostasis, the uptake and storage mechanisms are generally regulated by the transcriptional repressor Zur, while efflux systems are regulated by different transcription activators. Caulobacter crescentus, an oligotrophic alfa-proteobacterium, has in its genome several genes potentially involved in uptake, storage and efflux of zinc. In this work, a global analysis of genes differentially expressed in response to zinc excess and starvation will be carried out using DNA microarrays. Transcriptional fusions of promoters to the lacZ reporter gene will be used to validate the results obtained in microarrays and also to identify Zur binding sites. The consensus sequence obtained will be used for an in silico analysis of the whole genome intergenic regions in order to find genes which are not present in DNA microarrays. The validation of these sites will be done by in vitro biochemical techniques and also by analysis of the expression of these genes in a zur mutant strain.
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