Positive Regulation of Spoilage Potential and Biofilm Formation in OS155 via Quorum Sensing System Composed of DKP and Orphan LuxRs.

The spoilage potential and biofilm formation of are reported to be regulated by Quorum sensing (QS) system from the phenotype point of view, but the specific mechanism is not fully understood. In the present study, the QS autoinducers were detected by UHPLC-MS/MS, cell density-dependent -type genes were obtained through autoregulation experiments among a series of candidates in OS155 (The SSO of large yellow croaker). The direct interaction between cyclo-(L-Pro-L-Phe) (PP) and LuxR01 as well as LuxR02 proteins was revealed via binding assay. Deletion of -type genes ( and ) impaired spoilage potential and biofilm formation of OS155 in various degrees. Transcriptional analysis and qRT-PCR validation showed that spoilage and biofilm-related genes , and were down-regulated in 01 and 02 deletion strains. In addition, exogenous PP promoted spoilage potential and biofilm formation, which could be attenuated by 01 or 02 deletion. Our results revealed an explicit QS system employing PP as autoinducer and two orphan LuxRs as receptors which positively regulated spoilage capacity and biofilm formation via transcriptional regulation of corresponding genes in OS155, which provides potential specific targets for seafood preservation involving QS system.