The QseB/QseC two-component system modulates virulence, motility, and outer membrane vesicles biogenesis in...

Salmonella enterica serovar Enteritidis (S. Enteritidis) is a major foodborne pathogen responsible for gastroenteritis, whose pathogenicity is tightly regulated by complex molecular networks. Two-component systems (TCSs), as the principal bacterial signal transduction mechanisms, play a central role in environmental adaptation. Quorum sensing (QS) represents a universal chemical communication process by which bacteria perceive and interpret environmental cues. Among these systems, the QseB/QseC TCS acts as a key regulatory node linking QS signals to bacterial physiological responses. However, its downstream targets and regulatory mechanisms may differ substantially among species. In this study, we systematically elucidated the hierarchical regulatory roles of QseB/QseC in motility, biofilm formation, and outer membrane vesicles (OMVs) biogenesis in S. Enteritidis strain ATCC13076. Deletion of qseC markedly enhanced biofilm formation, adhesion, and invasion, as well as increased lethality in the Galleria mellonella infection model, whereas the ΔqseB mutant exhibited the opposite trend with significantly reduced virulence. In contrast, both qseB and qseC deletions impaired bacterial motility due to the downregulation of key flagellar genes (flhDC, fliC, motB). Notably, we uncovered a link between the QseB/QseC QS system and OMVs biogenesis: loss of qseC triggered excessive vesiculation, revealing that QseB/QseC finely tunes OMVs production and composition. The increased OMVs release was accompanied by reduced protein and lipid content per vesicle, indicating a trade-off between OMVs quantity and quality - a phenotype with profound implications for bacterial communication in S. Enteritidis. These findings deepen our understanding of QseB/QseC as a central hub integrating QS signals with motility, virulence, and OMVs-mediated intercellular communication, highlighting their complex interplay in regulating S. Enteritidis pathogenesis and providing new insights into Salmonella pathogenesis and potential antivirulence strategies.