Of viral friends and viral foes: New adventures in the world of bacterial immunity

The billion-year arms race of bacteriophages with their bacterial hosts has inspired concepts and tools of fundamental microbiology since its first golden era almost a century ago. However, most work on phage-host interactions has so far focused on only a few model phages and thus left a vast potential of viral diversity and antiviral defenses untapped.
We have therefore composed a “BASEL collection” of around 70 new phages covering the major viral groups infecting Escherichia coli. The assorted diversity within and between these different groups makes the BASEL collection a powerful tool to study any aspect of phage-host interactions, and we have already shared these phages with dozens of laboratories around the world for their own research. In my talk I will show known as well as completely new anti-phage defense systems as examples of how we use the BASEL collection to systematically unravel the molecular mechanisms of bacterial immunity. Furthermore, I will present an upcoming expansion pack of BASEL phages featuring viral groups that could previously not be sampled until we bypassed different limitations of E. coli laboratory strains by innovative approaches. Taken together, our work shows how thinking outside the box of traditional model systems is opening the door to new worlds of fascinating molecular microbiology.