Still Something to Discover: Novel Insights into Escherichia coli Phage Diversity and Taxonomy

The aim of this study was to gain further insight into the diversity of Escherichia coli phages followed by enhanced work on taxonomic issues in that field. Therefore, we present the genomic characterization and taxonomic classification of 50 bacteriophages against E. coli isolated from various sources, such as manure or sewage. All phages were examined for their host range on a set of different E. coli strains, originating, e.g., from human diagnostic laboratories or poultry farms. Transmission electron microscopy revealed a diversity of morphotypes (70% Myo-, 22% Sipho-, and 8% Podoviruses), and genome sequencing resulted in genomes sizes from similar to 44 to similar to 370 kb. Annotation and comparison with databases showed similarities in particular to T4- and T5-like phages, but also to less-known groups. Though various phages against E. coli are already described in literature and databases, we still isolated phages that showed no or only few similarities to other phages, namely phages Goslar, PTXU04, and KWBSE43-6. Genome-based phylogeny and classification of the newly isolated phages using VICTOR resulted in the proposal of new genera and led to an enhanced taxonomic classification of E. coli phages.