Organisms can evolve different defences in response to pathogen infection. My lab studies the interactions between bacteria and their viruses (bacteriophage, phage) to understand how environmental variables drive the evolution of different defence strategies. The bacteria that we study, Pseudomonas aeruginosa, is an important opportunistic human pathogen that a number of different defence strategies to protect itself against phage infection, including an adaptive immune system (known as CRISPR-Cas) and various innate defences (e.g. phage receptor mutation). I will discuss how and why certain environmental variables tip the balance in the evolution of these defences and their long-term evolutionary and coevolutionary consequences. I will also discuss how being able to predict and manipulate the evolution of phage resistance can help to optimize the therapeutic application of phage.

Westra performed his PhD at Wageningen University, the Netherlands, on the mechanism and regulation of CRISPR-Cas immune systems. Following his PhD (2013, awarded with distinction) he obtained a Marie Curie Fellowship and a NERC Independent Research Fellowship to study evolutionary aspects of CRISPR-phage interactions at the University of Exeter, where he was offered a chair in 2019. Westra received a number of prestigious awards for his work, including the Heineken Young Scientists Award, the Fleming Award and the Philip Leverhulme Prize, and he was finalist for the Blavatnik Young Scientist Awards in 2020 and 2021. His research group currently consists of 4 PhD students and 5 postdocs who study various aspects of the ecology and evolution of phage-bacteria interactions. His research is funded by NERC, BBSRC, Wellcome and Leverhulme Trusts and the ERC. Westra is Director of Research of Biosciences at the Penryn campus, and leads the University of Exeter Microbiology Network, the Microbes and Society Network, and is the lead organizer of the biannual CRISPR ecology and evolution conference