Iron is a key nutrient for any microorganism having an important role in cellular metabolism and the expression of numerous virulence factors in pathogenic bacteria. One of the strategies used by bacteria to capture iron is the synthesis and secretion of siderophores which are molecules that have high affinity to ferric ions. This iron uptake system involves a series of genes whose expression is controlled mainly by the transcriptional regulator Fur. The regulator Fur complexes with ferrous ion and this complex binds to specific sequences, called Fur boxes, located in the promoter region of target genes, leading to repression of transcription of these genes. Klebsiella pneumoniae is a gram-negative bacterial pathogen that causes a variety of infections such as pneumonia, meningitis, septicemia, among others. K. pneumoniae has three iron acquisition systems, each mediated by siderophores aerobactin, yersiniabactin and enterobactin. Among the iron acquisition systems described in K. pneumoniae, the siderophore enterobactin is the most prevalent in clinical isolates and contribute decisively to a more virulent phenotype in these bacteria. Although several studies have shown an association between genes of the iron uptake system and virulence in K. pneumoniae, few studies with K. pneumoniae have issued the mechanisms of expression regulation of these genes and the role of iron in this regulation. Therefore, this work aims to validate the Fur boxes found within the promoter region of the enterobactin gene cluster in Klebsiella pneumonia, and to investigate putative bidirectional function of these boxes.
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