Oxidative stress constrains evolution of bacteriophage host-range diversity.

Abstract

Reactive oxygen species are essential for cellular signalling and redox homeostasis, but their accumulation causes cellular oxidative stress. In inflammatory bowel disease, oxidative stress is linked to chronic inflammation and alterations in the gut microbiota. We hypothesised that these alterations may result from the impact of reactive oxygen species on the interactions between bacteria and their viruses, bacteriophages. We followed the evolution of three Escherichia coli strains and a virulent bacteriophage in a chemostat under continuous growth and studied the impact of oxidative stress on this community. We show that both the bacteriophage and its three hosts persisted in the system over 10 days, but the relative abundance of bacteriophages was decreased in the presence of reactive oxygen species. Oxidative stress also limited bacteriophage population diversity by favouring the selection of specialist bacteriophages with a narrower host range. Concomitantly, reactive oxygen species accelerated the evolution of bacterial resistance to bacteriophages and drove the fixation of genomic mutations in genes related to cell surface structures or located in mobile genetic elements. These results highlight that oxidative stress impacts the evolutionary dynamics between bacteria and bacteriophages with consequences for microbiota diversity and potential implications in the context of intestinal inflammation.