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J. Bacteriol. doi:10.1128/JB.01201-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Identification of Genes Regulated by the cepIR Quorum Sensing System in Burkholderia cenocepacia by High-Throughput Screening of a Random Promoter Library

Department of Microbiology and Infectious Diseases, University of Calgary Health Sciences Center, Calgary, AB, Canada T2N4N1

^* To whom correspondence should be addressed. Email: psokol{at}ucalgary.ca.

	Abstract

The Burkholderia cenocepacia cepIR quorum sensing system regulates expression of extracellular proteases, chitonase, and genes involved ornibactin biosynthesis, biofilm formation, and motility. In a genome wide screen we identified cepIR regulated genes by screening a random promoter library of B. cenocepacia K56-2 constructed in a luminescence reporter detection plasmid for differential expression in response to N-octanoyl-L-homoserine lactone (OHL). Eighty nine clones were identified, 58 in which expression was positively regulated and 31 in which expression was negatively regulated by cepIR. The expression profiles of the 89 promoter clones were compared in the cepI mutant, K56-dI2, in medium supplemented with 30 pM OHL and K56-2 to confirm that the presence of OHL restored expression to wild type levels. To validate the promoter library observations and determine the effect of a cepR mutation on expression of selected genes, the mRNA levels of nine genes whose promoters were predicted to be regulated by cepR were quantitated by qRT-PCR in the wild type, cepI and cepR mutants. The expression levels of all nine genes were similar in the cepI and cepR mutants and consistent with the promoter-lux reporter activity. The expression of four selected cepIR regulated gene promoters was examined in a cciIR mutant and two of these promoters were also regulated by cciIR. This study extends our understanding of genes for which expression is influenced by cepIR and indicates the global regulatory effect of the cepIR system in B. cenocepacia.