Salicylate Treatment of Escherichia coli B23 with Capsular Polysaccharide Induced by Sub-Lethal levels of Kanamycin does not Sensitize the Cells to T7 Bacteriophage Adsorption

Abstract

Escherichia coli B23 can use capsular polysaccharide as a defense mechanism against T7 phage and certain antibiotics. Previous studies have shown that exposure of cells to sub-lethal concentrations of the aminoglycoside antibiotic kanamycin upregulates production of capsular polysaccharides. Given the role played by the bacterial capsule in resisting bacteriophage infection, we hypothesized that pre-treatment of cells with sublethal concentrations of kanamycin would protect against T7 phage adsorption. In this investigation, phage adsorption assays were performed on kanamycin-treated E. coli B23 cultures followed by salicylate capsule stripping. Kanamycin-treated samples were found to have a relatively constant amount of unadsorbed phage from 0 to 8 minutes of coincubation with E. coli B23, while untreated samples had up to 6.7 times more adsorbed phage in the same length of incubation. Our results demonstrate that the kanamycininduced capsule of E. coli B23 cells is protective and correlates to decreased phage adsorption.