A LysR family transcriptional regulator modulates biofilm formation and protease production in Burkholderia cenocepacia.

Quorum sensing (QS) signals are widely employed by bacteria to regulate biological functions in response to cell densities. Previous studies showed that Burkholderia cenocepacia mostly utilizes two types of QS systems, including the N-acylhomoserine lactone (AHL) and cis-2-dodecenoic acid (BDSF) systems, to regulate biological functions. We demonstrated here that a LysR family transcriptional regulator Bcal3178 controls the QS-regulated phenotypes, including biofilm formation and protease production, in B. cenocepacia H111. Expression of Bcal3178 at transcriptional level was obviously down-regulated in both the AHL-deficient and BDSF-deficient mutant strains comparing to the wild-type H111 strain. It was further identified that Bcal3178 regulated target gene expression by directly binding to the promoter DNA regions. We also revealed that Bcal3178 was directly controlled by the AHL system regulator CepR. These results show that Bcal3178 is a new downstream component of the QS signaling network that modulates a subset of genes and functions co-regulated by the AHL and BDSF QS systems in B. cenocepacia. IMPORTANCE Burkholderia cenocepacia is an important opportunistic pathogen in humans, which utilizes the BDSF and AHL quorum sensing (QS) systems to regulate biological functions and virulence. We demonstrated here that a new downstream regulator Bcal3178 of the QS signaling network controls biofilm formation and protease production. Bcal3178 is a LysR family transcriptional regulator modulated by both the BDSF and AHL QS systems. Furthermore, Bcal3178 controls many target genes which are regulated by the QS systems in B. cenocepacia. Collectively, our findings depict a novel molecular mechanism with which QS systems regulate some target gene expression and biological functions by modulating the expression level of a LysR family transcriptional regulator in B. cenocepacia.