Phage growth rate is significantly affected by host-temperature and phage-temperature interactions

Virus growth depends on host performance in any given environment and has a profound impact spanning fields from climate change to human health. We investigated the intrinsic growth rate of two natural G4-like bacteriophages on four clones of their host (E.coli strain C) that differed in their thermal performance, with significant differences in their maximum growth rate and optimum temperature. The intrinsic population growth rate of the G4-like phage isolates was measured on the four host clones at three temperatures, reflective of a low, optimum and high temperature for one of the phage. The phages intrinsic growth rate was significantly affected by host-temperature and phage-temperature interactions, but not by the interaction between host and phage. Across temperatures, phage growth rate was consistently highest on the host clone with the highest maximum growth rate, but was not, contrary to our expectations, lowest on the host with the lowest growth rate. At any given temperature, phage growth rate followed a directional trend with host growth rate, but this trend was not as apparent when looking between temperatures. Our work demonstrates a significant impact of temperature and the host on phage growth rate, but much work remains to be done to disentangle how variation in host performance impacts virus performance across temperatures.