Transcriptional regulation of Pseudomonas aeruginosa rhlR, encoding a quorum-sensing regulatory protein

Abstract

ThePseudomonas aeruginosa rhlRgene encodes the transcriptional regulator RhlR which has a central role in the quorum-sensing response. Different gene products involved in bacterial pathogenesis are regulated at the transcriptional level by two quorum-sensing response systems, Las and Rhl. The expression ofrhlRhas been reported to be under the control of the Las system, but its transcriptional regulation has not been studied in detail. Here, therhlRpromoter region has been characterized and shown to present four different transcription start sites, two of which are included in the upstream gene (rhlB) coding region. It was found thatrhlRexpression is not only dependent on LasR but also on different regulatory proteins such as Vfr and RhlR itself, and also on the alternative sigma factorσ54. It is reported thatrhlRexpression is partially LasR-independent under certain culture conditions and is strongly influenced by environmental factors.