For convenient comparison, these activity values of wild-type strain were defined as 100% and used to normalize the activities check details of other strains. The data presented are the means of three replicates and error bars represents the standard deviation. The impact of BDSF and AHL Smoothened inhibitor signaling systems on B. cenocepacia H111 pathogenicity The impact of BDSF and AHL systems on B. cenocepacia virulence was evaluated by using C. elegans

infection models. Agreeable with the previous reports [14, 22], deletion of either rpfF Bc or cepI led to an reduction of virulence in both slow killing and fast killing assays of C. elegans (Figure 6A, 6B). Remarkably, deletion of both rpfF Bc and cepI completely or almost completely abolished the bacterial virulence against C. elegans (Figure 6A, 6B). Figure 6 Influence of RpfF Bc and CepI on the virulence of B. cenocepacia against C. elegans. (A) Mutants ∆rpfFBc (∆), ∆cepI (●) and ∆rpfFBc∆cepI (○) showed the reduced virulence compared with their parental wild-type strain H111 (□) in slow killing (A) and fast killing (B) assays. OP50 was used as the mock control. The data presented are the mean of triplicate experiments and the error bars represents the standard deviations. Discussion Many bacterial pathogens contain either AHL- or DSF-type QS systems in coordination of

bacterial physiology. The human opportunistic pathogen B. cenocepacia is one of the exceptions which contain

both BDSF and AHL signaling mechanisms [7, 12, 13, 15, 19, 23]. In this study, we Blebbistatin ic50 have investigated the relationship of the two QS systems in signaling modulation of bacterial physiology and virulence. Although the recently published results believe that the BDSF and AHL systems control overlap set and specific genes [17, 18], we found second that the two QS systems exert cumulative effect on bacterial motility, biofilm formation and virulence factor production (Figure 5A-C). In addition, we showed that BDSF regulates AHL signal production by influencing the c-di-GMP phosphodiesterase activity of its receptor RpfR. Given that both QS systems are widely conserved in the members of B. cepacia complex [7, 10], it would be of great interest to investigate whether the similar cross-talking mechanisms of the AHL and BDSF systems are conserved in other members of the Burkholderia species. The intracellular signal c-di-GMP is a widely conserved second messenger, which is known to be involved in the regulation of a range of biological activities, including bacterial motility, biofilm formation and virulence factor production [10, 24, 25]. The research progress over the last few years shows that c-di-GMP commonly controls various biological functions through interacting with different receptor or effector proteins, such as PilZ, FleQ, VpsT, LapD, FimX, PelD, and Clp [26–32].