Anthranilamide from Streptomyces spp. inhibited Xanthomonas oryzae biofilm formation without affecting cell growth

Xanthomonas oryzae (Xoo) causes bacterial blight in rice, which reduces crop yield and leads to significant economic damage. Xoo exerts its pathogenicity by biofilm formation, interfering with sap flow in the xylem vessels. Inhibition of Xoo biofilm formation may therefore alleviate the symptoms of bacterial blight and restore rice yields. Streptomyces spp. are soil bacteria that produce various secondary metabolites. In the present study, 38,888 extracts derived from Streptomyces spp. were screened for their ability to inhibit Xoo biofilm formation; four extracts exhibited strong inhibitory activity. Separation and purification of the extracts from strains 0320 and 4359 suggested that anthranilamide was the chemical responsible for this effect. Anthranilamide was found to inhibit biofilm formation without affecting Xoo cell growth; it is, therefore, a good candidate chemical for the treatment of bacterial blight in rice as it will not give rise to resistant bacterial strains. The selected four Streptomyces strains were also good candidates for biological treatment of bacterial blight in rice.