Silver nanoparticles complexed with bovine submaxillary mucin possess strong antibacterial activity and protect against seedling infection

A simple method for the synthesis of nanoparticles (NPs) of silver (Ag) in a matrix of bovine submaxillary mucin (BSM) was reported previously by some of the authors of this study. Based on mucin characteristics such as long-lasting stability, water solubility, and surfactant and adhesive characteristics, we hypothesized that these compounds, named BSM-Ag NPs, may possess favorable properties as potent antimicrobial agents. The goal of this study was to assess whether BSM-Ag NPs possess antibacterial activity, focusing on important plant-pathogenic bacterial strains representing both Gram-negative (Acidovorax and Xanthomonas) and Grampositive (Clavibacter) genera. Growth inhibition and bactericidal assays, as well as electron microscopic observations, demonstrate that BSM-Ag NPs, at relatively low concentrations of silver, exert strong antimicrobial effects. Moreover, we show that treatment of melon seeds with BSM-Ag NPs effectively prevents seed-to-seedling transmission of Acidovorax citrulli, one of the most threatening pathogens of cucurbit production worldwide. Overall, our findings demonstrate strong antimicrobial activity of BSM-Ag NPs and their potential application for reducing the spread and establishment of devastating bacterial plant diseases in agriculture.