Identification of LuxR Family Regulators That Integrate Into Quorum Sensing Circuit in Vibrio parahaemolyticus

Vibrio parahaemolyticus is one of the most important food-borne pathogens that cause economic and public health problems worldwide. Quorum sensing (QS) is a way for the cell-cell communication between bacteria that controls a wide spectrum of processes and phenotypic behaviors. In this study, we performed a systematic research of LuxR family regulators in V. parahaemolyticus and found that they influence the bacterial growth and biofilm formation. We then established a QS reporter plasmid based on bioluminescence lux CDABE operon of Vibrio harveyi and demonstrated that several LuxR family regulators integrated into QS circuit in V. parahaemolyticus . Thereinto, a novel LuxR family regulator, named RobA, was identified as a global regulator by RNA-sequencing analyses, which affected the transcription of 515 genes in V. parahaemolyticus . Subsequent studies confirmed that RobA regulated the expression of the exopolysaccharides (EPS) synthesis cluster and thus controlled the biofilm formation. In addition, bioluminescence reporter assays showed that RobA plays a key role in the QS circuit by regulating the expression of opaR , aphA , cpsQ-mfpABC , cpsS , and scrO . We further demonstrated that the regulation of RobA to EPS and MfpABC depended on OpaR and CpsQ, which combined the QS signal with bis-(3′-5′)-cyclic dimeric GMP to construct a complex regulatory network of biofilm formation. Our data provided new insights into the bacterial QS mechanisms and biofilm formation in V. parahaemolyticus .