| Summary: | <p>Abstract</p> <p>Background</p> <p>The <it>Burkholderia cenocepacia </it>CepIR quorum sensing system has been shown to positively and negatively regulate genes involved in siderophore production, protease expression, motility, biofilm formation and virulence. In this study, two approaches were used to identify genes regulated by the CepIR quorum sensing system. Transposon mutagenesis was used to create <it>lacZ </it>promoter fusions in a <it>cepI </it>mutant that were screened for differential expression in the presence of <it>N</it>-acylhomoserine lactones. A bioinformatics approach was used to screen the <it>B. cenocepacia </it>J2315 genome for CepR binding site motifs.</p> <p>Results</p> <p>Four positively regulated and two negatively regulated genes were identified by transposon mutagenesis including genes potentially involved in iron transport and virulence. The promoter regions of selected CepR regulated genes and site directed mutagenesis of the <it>cepI </it>promoter were used to predict a consensus <it>cep </it>box sequence for CepR binding. The first-generation consensus sequence for the <it>cep </it>box was used to identify putative <it>cep </it>boxes in the genome sequence. Eight potential CepR regulated genes were chosen and the expression of their promoters analyzed. Six of the eight were shown to be regulated by CepR. A second generation motif was created from the promoters of these six genes in combination with the promoters of <it>cepI</it>, <it>zmpA</it>, and two of the CepR regulated genes identified by transposon mutagenesis. A search of the <it>B. cenocepacia </it>J2315 genome with the new motif identified 55 <it>cep </it>boxes in 65 promoter regions that may be regulated by CepR.</p> <p>Conclusion</p> <p>Using transposon mutagenesis and bioinformatics expression of twelve new genes have been determined to be regulated by the CepIR quorum sensing system. A <it>cep </it>box consensus sequence has been developed based on the predicted <it>cep </it>boxes of ten CepR regulated genes. This consensus <it>cep </it>box has led to the identification of over 50 new genes potentially regulated by the CepIR quorum sensing system.</p>
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