The net effect of microbial siderophores on above- and belowground soil health

The production of mine waste comes at great socio-economic and environmental costs. There is a clear need for the development of sustainable strategies that allow for rapid recovery of mining sites with minimal intervention. Microbes play an important role in geochemical processes and their vast metabolic diversity may aid in the clean-up of mine-degraded soils.

Importantly, detoxification in microbial communities not only depends on individual behaviour, but on the collective action of different species. Our knowledge of how different species interact with one another to detoxify metals is limited.

We have identified a key collectively acting detoxifying trait: siderophores. Microbes release these compounds into the environment in response to metals stress, where upon chelation the toxic metal is prevented from being taken up and killing microbial cells. Because detoxification takes place outside of the cell, siderophores not only protect the producer from toxic metal stress, but potentially any individual growing in the near vicinity.

Siderophores are therefore open to exploitation by non-producing 'cheats' that do not contribute their fair share but reap the benefits associated with their production. Community-wide siderophore levels are thus shaped by a balance between local detoxifying benefits and costs associated with exploitation. Our understanding of the ecological constraints driving the evolution and quantity of community-wide siderophore production is limited.

Siderophores not only determine microbial interactions, but also play a role in plant-microbe feedbacks by altering metal availability. We have little understanding of how such feedbacks are affected by cooperation within the rhizosphere.

The first aim of the project is to determine how theoretically important variables (i.e. spatial structure and resources) affect siderophore production and detoxification, using several approaches: (i) analytical/numerical models to examine how interactions within and between species affect community-wide siderophore production under different ecological constraints. (ii) experimental evolution to verify theoretical predictions. (iii) soil chemical analyses to determine collective detoxification. (iv) genomics/transcriptomics to determine the genetic changes (mutation versus gene regulation) underpinning phenotypic changes in siderophore production.

The second aim is to determine how siderophore-based cooperation in the rhizosphere affects the efficacy of phytoremediation, i.e. the synergistic action between plants and microbes to clean up toxic metal waste. This part of the project will primarily use potting experiments - comparing the performance of plants grown with microbial communities that have diversified in terms of their siderophore production.

The interdisciplinary nature of the project - and expertise of the supervisory team - allows the candidate to prioritise certain aspects over others and to flexibly adapt and co-create the project to match their interest.