Modelling the effects of climate change on the interaction between bacteria and phages with a temperature-dependent lifecycle switch.

Ongoing climate change and human activities alter the population dynamics of pathogenic bacteria in natural environments, increasing the risk of disease transmission. Among the key mechanisms of amplification of bacteria in the environment is the alteration of the natural control by their enemies, bacteriophages. Using mathematical modelling, we explore how climate change and implementation of certain agricultural practices affect interactions of bacteria with phage exhibiting condition-dependent lysogeny, where the type of phage infection lifecycle is determined by the ambient temperature. As a case study, we model alteration to the control of the pathogenic bacteria Burkholderia pseudomallei by its dominant phage. B. pseudomallei causes melioidosis, which is among the deadliest infections in Southeast Asia and across the tropics. We use historical records for UV radiation and temperature in Thailand covering the period 2009-2023 to assess the density of the phage-free pathogen, capable of causing infection. We also predict phage-pathogen dynamics for the period 2024-2044. We apply both non-spatial and spatial models to mimic B. pseudomallei population dynamics in the surface water of rice fields and in soil. Our models predict a drastic increase in pathogen density due to less efficient control by the phage which is caused by global warming. We also find that some of the current agricultural practices would enhance the risk of acquisition of melioidosis by altering densities of the pathogen in the environment.