DUAL BEHAVIOUR OF PLANTS AGAINST BACTERIAL QUORUM SENSING: INHIBITION OR EXCITATION

E. Mahmoudi, S. Tarzaban, P. Khodaygan

Abstract


Bacteria use an unique and sophisticated system for regulating diverse physiological processes in function of their population size. This regulatory procedure, called “quorum sensing” (QS), depends on the synthesis and perception between bacteria of small signal molecules such as acyl-homoserine lactones (AHLs). It is now evident that plants can listen to bacterial signals and respond in sophisticated ways to the information. The anti-QS activity of the methanolic extract of 44 plant species was detected through the inhibition of the QS-related violacein pigmentation in Chromobacterium violaceum CV026 in the presence of 5 mgl-1 of C6- homoserin lactone. In addition, the ability of test plants to produce AHL-mimicking compounds that excite QS-related response in CV026 was investigated. The results revealed that the QS inhibition activity was observed in the leaves and stem extracts of tarragon (Artemisia dracunculus), radish (Raphanus sativus) and hollyhock (Althea officinalis), which repress violacein production in CV026. We have also shown that Trifolium repens contains AHL- mimicking molecules that can activate QS function in biosensor bacterium and induce violacein production in CV026. Methanolic extracts were also able to inhibit QS-regulated virulence in Pectobacterium carotovorum subsp. carotovorum on potato tubers. The results suggest that plants have quorum sensing-mimicking signals that could potentially be used for disrupting quorum sensing of associated bacteria thus controlling their infections.

Keywords


Anti-QS activity; quorum sensing excitation; Pectobacterium; plant extract

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DOI: http://dx.doi.org/10.4454/JPP.V96I2.041

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