Soil phyllosilicate and iron oxide inhibit the quorum sensing of Chromobacterium violaceum

Microorganisms respond to various adverse environmental conditions and regulate different physiological functions by secreting and sensing signal molecules through quorum sensing (QS) systems. Phyllosilicates and iron oxides present in soils and sediments may have substantial impact on bacterial activity and QS due to their unique reactivity and close association with microorganisms. This research explored the effect of goethite, montmorillonite and kaolinite (0.05–2g L−1) on the growth and QS of a bacterial model, Chromobacterium violaceum. The results showed that kaolinite and goethite caused cellular damage at low mineral concentrations. The capacity for violacein production and biofilm formation of C. violaceum were inhibited by the minerals in the order of kaolinite > goethite > montmorillonite. The possible underlying mechanisms for QS inhibition by different minerals were investigated. Specifically, kaolinite repressed QS function through downregulation the expression of signal molecules synthesis gene cvil. Goethite and montmorillonite interfered with QS by adsorption of extracellular signal molecules. This work provides a better understanding of the interactions between bacteria and minerals and proposed that the inhibition of QS system is an ignored mechanism for bacterial toxicity by phyllosilicates and iron oxides.