Iron has an essencial role on the transcriptional regulation of many genes related to the bacterial pathogenesis, such as those related to biofilm formation and the expression of toxins, fimbriaes, capsules and proteases. The role of iron is mediated by the repressor Fur. Fur, encoded by fur gene, regulates gene expression by binding to DNA regulatory sequences, known as Fur boxes, located in the promoter region of the target genes. Klebsiella pneumoniae is a gram-negative opportunistic pathogen that may causes a variety of infections, such as pneumonia, meningitis, septicemia, among others. Few studies in K. pneumoniae have shown the role of iron, through the Fur repressor, on the expression regulation of virulence genes.An essential step during colonization is the adhesion of the bacteria to mucosal surfaces of the host followed by biofilm formation. In this sense, fimbriae and capsular polysaccharide are important surface structures that contribute to pathogenisis of K. pneumoniae. While fimbriae are essencial for the biofilm formation predominantly during the initial stages, enabling the cells to adhere to both biotic and abiotic surfaces, the capsules are associated with the maturation and later developmental stages of the biofilm. Considering that so far none study has shown that the expression of fimbriae and capsules may be controlled by Fur in a coordinated manner, this work aims to validate the potential Fur boxes found on the promoter region of genes encoding fimbriae and capsules on K. pneumoniae, and to investigate the role of iron and repressor Fur on the co-regulation of the expression of those surface structures.
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