The Reduction of T7 Phage Adsorption in Escherichia coli B23 Cells Treated with Sub-Lethal Levels of Kanamycin

Abstract

The production of capsular material has been implicated as a bacterial defence mechanism against certain antibiotics and against phage adsorption. The capsule acts to block the phage from binding to its receptor on the bacterial cell which effectively inhibits phage adsorption. Previously, it has been shown that exposing Escherichia coli B23 cells to sub-inhibitory levels of the antibiotic kanamycin results in an increase in extracellular polysaccharide production, possibly in the form of a capsule. In the current study, this phenomenon was investigated using T7 phage adsorption as a model to assess the presence of a capsule. Phage adsorption assays were performed on both E. coli B23 cells treated with sub-lethal levels of kanamycin for 1 hour and untreated cells. T7 phage adsorption was shown to be diminished in E. coli treated with antibiotic, as compared to those which had not been treated with antibiotic. This decrease in phage adsorption to the antibiotic treated cells suggests that the induced extracellular polysaccharide produced by these cells is part of the capsule. Thus, this work provides further insight into the likely nature of the induced-extracellular polysaccharide produced by these cells following antibiotic treatment.