| Pseudomonas bacteria and phage have previously been shown to undergo reciprocal cycles of antagonistic co-evolution, whereby bacteria evolve resistance to phage, and phage evolve to overcome this resistance. Laboratory studies have been instrumental in demonstrating the causes and consequences of this process but it is currently unknown how these findings translate into the natural soil habitat of these organisms. I aim to elucidate how antagonistic co-evolution shapes the diversity of natural Pseudomonas and phage populations in space and time. First, I will provide evidence of bacteria-phage co-evolution under (semi)natural conditions. Soil microcosms will be inoculated with genetically marked Pseudomonas and associated phage. The bacteria and phages will be isolated from soil after prolonged periods to test whether bacteria are able to evolve resistance to phages, and in turn, whether bacteria evolve to overcome this resistance. I will also determine the effects of theoretically important variables (environmental quality and perturbations) on co-evolution. Second, I will investigate if signatures of co-evolutionary dynamics ? adaptation of phages to their local bacterial populations - can be detected in soil populations. I will isolate phage and Pseudomonas from soil samples collected on a scale spanning five orders of magnitude, and then measure interactions between bacteria and phages across space and time. |
