Escherichia coli Biofilm Development and Bacteriophage T4 Susceptibility

Abstract

Previous studies demonstrated that the varying physiological properties of the stationary phase cells of Escherichia coli can cause varying susceptibility to T4 at different ages of the culture. These studies did not take into account that stationary phase bacteria include both free-floating and biofilm cells. In this study, we sought to distinguish whether free-floating or biofilm cells were responsible for the unusual patterns observed. Glass tubes of LB medium inoculated with E.coli ZK126 were grown for 1 to 7 days. Free-floating cells were separated from the biofilm and both were infected with T4 Bacteriophage. A standard plaque assay was performed to determine the progeny produced upon infection of the cells. Infection of the free floating cells yielded low amounts of progeny when stationary phase was not yet established; once established, no viral progeny were observed. On the contrary, successful infection of the biofilm cells was observed on day 4 while very little progeny was observed on preceding and following days. This suggests that the peak of viral progeny observed in previous studies was due to changes of physiological properties of the biofilm rather than the free floating cells. The biofilm might have exhibited such a pattern due to OmpC over-expression at this stage of biofilm development. OmpC was previously proven to aid viral attachment to bacterial cells.