Escherichia coli is a highly versatile and adaptable species, exhibiting high degree of diversity and consisting of both harmless commensals and pathogenic variants. In fact, only 20% of the genes of the E. coli genome are shared among all strains, and there are over 200 serotypes based on somatic (O), capsular (K), fimbrial (F) and flagellar (H) antigens. The E. coli surface diversity has fostered highly diverse phages using many different host receptors and infection strategies, with most phages only infecting a subset of E. coli. Yet, our understanding of E. coli phage sensitivity is far from complete.

Here we aim to identify broad phage sensitive E. coli. The E. coli Reference Collection (ECOR) is a set of 72 reference strains isolated from a variety of hosts and geographical locations representing most of the genetic diversity of E. coli. Using the ECOR as host panel, we isolated 128 phages from a variety of environmental samples. When screening environmental samples for phages, some ECOR strains were positive for only a few samples, however plaques could be observed from all samples on E. coli ECOR4. Interestingly, in a subsequent host range analysis we found that ECOR4 was also sensitive to 53 (41%) of the isolated phages that otherwise had different host ranges. To identify common genetic elements of the 53 phages we are currently performing whole genome sequencing using MiSeq, and initial results indicate that different phage types are able to infect ECOR4. To elucidate the underlying mechanisms of ECOR4 broad phage sensitivity, we have set out to identify phage receptors and other genes required for infection by constructing Tn5 transposon libraries in ECOR4 and testing for phage sensitivity. Due to its unusual sensitivity to many diverse phages, ECOR4 can serve as a model for analyzing phage sensitivity in E. coli.