The effect of a temperature‐sensitive prophage on the evolution of virulence in an opportunistic bacterial pathogen

Viruses are key actors of ecosystems and have major impacts on global
biogeochemical cycles. Prophages deserve particular attention as they are
ubiquitous in bacterial genomes and can enter a lytic cycle when triggered
by environmental conditions. We explored how temperature affects the
interactions between prophages and other biological levels by using an
opportunistic pathogen, the bacterium Serratia marcescens, that harbours
several prophages and that had undergone an evolution experiment under
several temperature regimes. We found that the release of one of the
prophages was temperature-sensitive and malleable to evolutionary changes.
We further discovered that the virulence of the bacterium in an insect
model also evolved and was positively correlated with phage release rates.
We determined through analysis of genetic and epigenetic data that changes
in the bacterial outer cell wall structure possibly explain this
phenomenon. We hypothezise that the temperature-dependent phage release
rate acted as a selection pressure on S. marcescens and that it resulted
in modified bacterial virulence in the insect host. Our study system
illustrates how viruses can mediate the influence of abiotic environmental
changes to other biological levels and thus be involved in ecosystem
feedback loops.