Phenotypic and genotypic characterisation of Burkholderia cenocepacia J2315 mutants affected in homoserine lactone and diffusible signal factor-based quorum sensing systems suggests interplay between both types of systems. PLoS One 2013

Many putative virulence factors of Burkholderia cenocepacia are controlled by various quorum sensing (QS) circuits. These QS systems either use N-acyl homoserine lactones (AHL) or cis-2-dodecenoic acid (‘‘Burkholderia diffusible signal factor’’, BDSF) as signalling molecules. Previous work suggested that there is little cross-talk between both types of systems. We constructed mutants in B. cenocepacia strain J2315, in which genes encoding CepI (BCAM1870), CciI (BCAM0239a) and the BDSF synthase (BCAM0581) were inactivated, and also constructed double (DcepIDBCAM0581, DcciIDBCAM0581 and DcepIDcciI) mutants and a triple (DcepIDcciIDBCAM0581) mutant. Subsequently we investigated phenotypic properties (antibiotic susceptibility, biofilm formation, production of AHL and BDSF, protease activity and virulence in Caenorhabditis elegans) and measured gene expression in these mutants, and this in the presence and absence of added BDSF, AHL or both. The triple mutant was significantly more affected in biofilm formation, antimicrobial susceptibility, virulence in C. elegans, and protease production than either the single or double mutants. The DBCAM0581 mutant and the DcepIDBCAM0581 and DcciIDBCAM0581 double mutants produced significantly less AHL compared to the WT strain and the DcepI and DcciI single mutant, respectively. The expression of cepI and cciI in DBCAM0581, was approximately 3-fold and 7-fold (p,0.05) lower than in the WT, respectively. The observed differences in AHL production, expression of cepI and cciI and QS-controlled phenotypes in the DBCAM0581 mutant could (at least partially) be restored by addition of BDSF. Our dat