Schematic representation of the QS signalling networks in B. cenocepacia. RpfRBc and CepI are involved in synthesis of BDSF and AHL signals, respectively. Perception of BDSF by RpfR substantially enhances its c-di-GMP phosphodiesterases activity and causes a reduction of the intracellular c-di-GMP level, and consequently affects the cepI transcriptional expression level and a range of biological functions, including swarming motility, biofilm formation and virulence through an unknown c-di-GMP effector X. The AHL-dependent QS system is also implicated in regulation of motility, biofilm formation, and virulence through its cognate receptor CepR. Solid arrows indicate the signalling regulation or signal transport.