New insights into the antibacterial and quorum sensing inhibition mechanism of leaf extracts towards PAO1.

UNLABELLED

This study aimed to investigate the anti-quorum sensing (QS) activity of leaf extracts (AALE) towards PAO1 as well as the underlying molecular mechanisms. Using a biosensor CV026, AALE were found to have anti-QS activity as AALE treatment significantly inhibited the violacein production of CV026 while produced little effect on the cell growth. Beyond that a higher dosage of AALE inhibited cell growth, sub-MIC of AALE significantly reduced the production of QS-regulated virulence factors (pyocyanin, elastase, and rhamnolipid), biofilm formation, and the swarming and swimming motility in PAO1 with a dosage-dependent manner. Quantitative real-time PCR (qRT-PCR) analysis did not detect the direct inhibitory effect of AALE on the expression of QS genes (, , , and ). By iTRAQ-based quantitative proteomic analysis, 129 proteins were found to be differentially expressed upon AALE treatment, with 85 upregulated and 44 downregulated proteins, respectively. Functional enrichment analysis of the differential proteins revealed that AALE exerted anti-QS activity towards PAO1 by upregulating the expression of the global regulator CsrA, inducing oxidative stress, and perturbing protein homeostasis. Moreover, the inhibitory effect of AALE on the virulence of PAO1 was likely to be achieved by attenuating the expression of QS-regulated genes instead of QS genes. Collectively, the results of this study provide a basis for the future use of AALE as a preservative in controlling food spoilage caused by .

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02663-5.