Don't go out there! How do bacteria-phages interactions in the soil impact the rhizobia-legume symbiosis

Rhizobia (nitrogen-fixing bacteria) are a classic model for
mutualistic interactions - they form intimate intracellular
symbioses with legumes where they exchange nitrogen for
nutrients and shelter. The rhizobia-legume symbiosis has been
studied near-exclusively as a pairwise interaction, but in reality
is embedded within a complex species community with
consequences for each partner and thus the symbiosis.
Between plant-hosts rhizobia live as free-living bacteria within a
diverse soil microbial community including phages (bacterial
viruses) - the primary predators of bacteria. Phage predation
could shape the rhizobia-legume symbiosis in numerous ways;
phages drive continuous selection for phage resistance

(antagonistic coevolution) which may result in pleiotropic trade-
offs in the symbiosis. Conversely, higher mortality outside may

drive greater symbiotic investment by increasing the value of
protection within the plant, i.e. altering the 'economics' of the
interaction. In this project we will combine experimental
evolution, next-generation sequencing and mathematical
modelling to ask a critical overlooked question - how do
interactions outside the host shape the rhizobia-legume
symbiosis