Capsular Polysaccharide has a Minor Role on Streptomycin-Induced Reduction of T7 Phage Adsorption to Escherichia coli

Abstract

Extracellular polysaccharide production which forms an extracellular capsule has long been implicated in many bacterial defence mechanisms to a multitude of different environmental dangers, including antibiotic treatment. Previous research has shown that treating E. coli cells with sub-inhibitory levels of antibiotics increases capsular production, and this increase in capsule was correlated with a decrease in T7 phage adsorption. This decreased phage adsorption was previously attributed to the capsule physically interfering with the phage's ability to bind to lipopolysaccarides on the cell surface of the bacterial cell, which is necessary for viral DNA injection. In this study, we tested this hypothesis by comparing wild-type E. coli with a strain that was unable to produce capsular polysaccharide. We treated both strains with sub-inhibitory levels of streptomycin, and measured T7 phage adsorption. T7 phage adsorption was shown to be decreased in both wild-type and knockout strains, and the level of decrease was comparable with both samples. This suggests that antibiotic-induced capsular polysaccharide production plays a minor role in the observed decreased T7 phage adsorption, and other factors must be involved.