The Effect of Methanolic Extracts of Several Plants as Inhibitors of Quorum Sensing of the Cotton Angular Leaf Spot Bacterium, Xanthomonas citri subsp. malvacearum.

Abstract

The bacterial quorum sensing (QS) system regulates the expression of pathogenicity genes according to bacterial population density. Targeting QS is a novel approach to control bacterial infections. One method involves using extracts from medicinal plants. Therefore, this study examined the impact of methanolic extracts from various medicinal plants (Origanum syriacum, Eucalyptus tereticronis, and Moringa sp.) on the pathogenicity factors of the cotton angular spot bacterium Xanthomonas citri subsp. malvacearum (Xcm), that are regulated by quorum sensing (QS), such as growth and motility. The results obtained demonstrated the ability of the tested plant extracts to inhibit the growth of the bacteria XcmS101. The minimum inhibitory concentration (MIC) for all three extracts was 2.2, 3.7, 9.0 mg\mL, respectively. Whereas the effect on bacterial movement showed the ability of the plant extracts at concentrations that did not affect the growth of the bacteria, as the inhibition rate (%) of the movement of the bacteria XcmS101 at the two concentrations 1.565 and 0.78 mg\mL for the extracts Origanum syriacum and Eucalyptus tereticronis reached 55.00 and 35.15 %, respectively. Whereas the inhibition rate of the concentration 3.125 mg\mL of the Moringa. sp. extract reached 45 %.

Keywords:

QS, QS inhibitors, XcmS101, MIC, growth, motility.