Cranberry constituents interfere in Quorum Sensing of Vibrio harveyi

Quorum sensing affects various of physiological and viral properties of bacteria. It is well known that cell-cell signal system plays significant role in biofilm formation. Quorum Sensing is mediated by signal molecules known as autoinducers (AI).

Non dialyzable material of cranberry (NDM) affects oral bacterial pathogenicity and physiological pathways. Cranberry constituents inhibit dental biofilm formed by Streptococcus mutans.

Hypothesis:

We hypothesized that one of the means by which NDM affects oral biofilm is via interaction with bacterial cell-cell communication.

Materials and methods:

Using a bacterial of Vibrio harveyi and its two mutant strains, defected in AI-1 or AI-2 sensor, we determined the effect of cranberry constituents on bacterial signaling system. Each mutant strain was incubated with different concentrations of NDM or with NDM supplemented with spent medium containing AI-1or AI-2. Relative bioluminescence as indication for quorum sensing was recoded continuously

Results:

NDM inhibits all tested bacterial strains in dose-dependent manner. This effect was more pronounced on both mutants compared to wild type. Addition of exogenous AI-1 significantly reversed the inhibitory influence of NDM, while exogenous AI-2 had minor recovering effect on bioluminescence decreased by cranberry NDM.

Conclusion:

Since NDM's inhibitory effect was reversible and neutralized by addition of exogenous autoinducer, we hypothesized that NDM competes with signal molecule for binding to autoinducer sensor.

These findings revealed proposed mechanism of NDM effect on quorum sensing of Vibrio harveyi which could be further explored in investigation of cranberry anti-biofilm action in dental biofilm.