The role of symbiont community diversity for the rhizobia-legume symbiosis

Microbes are powerful things. This is particularly true for those engaged in intimate symbiotic interactions with other organisms. The relationship between Rhizobia and legumes, for example, plays a critical role in plant productivity in both natural and agricultural environments. Rhizobia fix atmospheric nitrogen and exchange this for sugars with their legume hosts, a relationship that accounts for ~50% of biological nitrogen fixation in agricultural systems. In agriculture, extensive use of man-made mineral fertilisers has become
unsustainable, damaging soils and contributing significantly to greenhouse gas emissions. Harnessing natural processes like the rhizobia-legume interaction has the potential to be a major step towards more sustainable agricultural practice, however, research into the ecology and evolution of these interactions is required.

Research into this interaction has typically focused on pairwise interactions between two genotypes. Yet, we know that plants typically form associations with multiple rhizobia genotypes simultaneously. At present, the relationship between symbiont communities and plant productivity is poorly understood. With this project, we will investigate the impact of rhizobia symbiont diversity on the establishment, resilience and productivity of this important host-microbe symbiosis. We will combine controlled lab and greenhouse experiments to
estimate the relationship between rhizobia diversity and symbiotic performance and identify the drivers of this relationship. We will examine the impact of diversity both on short (ecological) and long (evolutionary) timescales to investigate the impact of symbiont diversity on community stability over multiple host plant generations. Finally, we will work with industrial partners to develop and test the effectiveness of multi-strain inocula as a commercial application.

This project will draw on community ecology and biodiversity theory as well as host-microbe interactions and rapid bacterial evolution. You will have the opportunity to develop expertise in microbiology, experimental evolution, microbial ecology, plant biology and hypothesis-led experimental design. You will also have access to an extensive and fully sequenced strain collection to learn and develop bioinformatics and statistical skills as well as an opportunity to use cutting edge research facilities at both the universities of York and Sheffield. You will be supported and encouraged to develop your own ideas and hypotheses and will be part of larger research groups in both universities.

As this is an interdisciplinary project ideal candidates will have a background in or a demonstrated interest in at least one of the main subject areas – e.g. microbiology, community ecology, agricultural sustainability – and be willing to develop skills in the other areas.

The PhD will be co-supervised by Dr Ellie Harrison (University of Sheffield)