Impact of Quorum Sensing on the Virulence and Survival Traits of Burkholderia plantarii

Quorum sensing (QS) is a mechanism by which bacteria detect and respond to cell density, regulating collective behaviors. <i>Burkholderia plantarii</i>, the causal agent of rice seedling blight, employs the LuxIR-type QS system, common among Gram-negative bacteria, where LuxI-type synthase produces QS signals recognized by LuxR-type regulators to control gene expression. This study aimed to elucidate the QS mechanism in <i>B. plantarii</i> KACC18965. Through whole-genome analysis and autoinducer assays, the <i>plaI</i> gene, responsible for QS signal production, was identified. Motility assays confirmed that C8-homoserine lactone (C8-HSL) serves as the QS signal. Physiological experiments revealed that the QS-defective mutant exhibited reduced virulence, impaired swarming motility, and delayed biofilm formation compared to the wild type. Additionally, the QS mutant demonstrated weakened antibacterial activity against <i>Escherichia coli</i> and decreased phosphate solubilization. These findings indicate that QS in <i>B. plantarii</i> significantly influences various pathogenicity and survival traits, including motility, biofilm formation, antibacterial activity, and nutrient acquisition, highlighting the critical role of QS in pathogen virulence and adaptability.