Escherichia coli O Antigen Serotype O16 Is a Restriction Factor for Bacteriophage T4 Infection

07/13/2017

Chiu J, Croft C, Ng K​

Volume 3
Fall 2016 / Winter 2017

The infection of Escherichia coli by bacteriophage T4 has long been investigated, providing key insights into viral life cycles, genetics, and phage therapy to combat bacterial disease. Alterations in the structure of the bacterial outer membrane, including LPS and OmpC, have been shown to play a key role in determining the tropism of T4. O antigen is present in the outer membrane of various bacterial species, including certain pathogenic serotypes of E. coli. While O antigen has been demonstrated to convey resistance to bacteriophage infection in other bacterial species, its role in T4 resistance in E. coli has not been explored. Here, we demonstrate a novel role for E. coli O antigen in restricting bacteriophage T4 infection using a laboratory-adapted E. coli strain with restored O antigen synthesis. Compared to the parental substrain, the O antigen-producing substrain resisted bacteriophage lysis across all multiplicities of infection tested, and showed comparable growth kinetics with or without T4 infection. In contrast, T4 infection exhibited robust bacterial lysis for the parental, non-O antigen-producing substrain. We demonstrated that this protective effect was not attributable to irreversible binding to secreted factors. This strongly supports the notion that the presence of O antigen alone can alter a susceptible strain of E. coli to become resistant to bacteriophage lysis, and underscores the relevance of external bacterial modifications in the development of phage resistance.