Restoration of O antigen expression in Escherichia coli K-12 MG1655 confers bacteriophage resistance

Abstract

The objective of this review is to summarize research that has been done on O antigen-mediated bacteriophage resistance in E. coli K-12 and to investigate the potential mechanisms of resistance. The loss of O antigen expression in E. coli K-12 strains such as MG1655 is due to the disruption of wbbL gene with an IS5 element. Insertion of an intact wbbL gene from O antigen expressing strain of E. coli WG1 into the chromosome of E. coli MG1655 restored O antigen expression. The resulting strain, DFB1655 L9, is resistant to P1, T4, and T7 bacteriophages. Bacteriophage absorption was measured using qPCR and double agar plaque assays, which showed a greater number of bacteriophage in the supernatant of an O antigen producing E. coli strain. Visualization of T4 bacteriophage and host interactions using negative stain electron microscopy showed a reduced amount of bacteriophage on strains expressing O antigen. These data suggest that bacteriophage absorption may be inhibited by O antigen.  The review concludes by considering several steps in the bacteriophage life cycle at which O antigen may inhibit T4 infection.