Plants are colonized by diverse microbial communities whose balance is closely tied to their fitness and health. Optimization of plant-symbiont interactions could help improve agricultural sustainability but to succeed we need to understand them in the context of the formation, structure and function of natural microbial communities. Plant-associated microbial communities are open (constant movement of microbes into and out of the system). Despite this, the microbiota exhibits stability: Variation between similar plants is largely correlated to factors like location.
To shed light on these communities, can parallels can be drawn to simpler non-host systems? Anaerobic digesters have open, complex communities with stable, but different structures in digesters operated similarly in different locations. This is possible due to robust metabolic networks of functionally redundant, interacting microorganisms capped by a keystone species that together transform complex substrates into methane. We discovered in plants that microbe-microbe interactions driven by a keystone species play outsize roles in structuring microbial communities and stabilizing them to pathogen invasion.
These interactions remain mostly uncharacterized, so how can we determine if metabolic interactions are important? In anaerobic bioreactors, we looked across studies, finding that substrate type is a major factor for digester community structuring. We also controlled endproduct removal, resulting in recruitment of a keystone organism producing n-caproic acid and in an efficient and stable metabolic network for liquid biochemical production. The questions are simple but technically challenging: What resources are available to colonizers of plants and how do they alter these resources? We are developing systems to evaluate the effect of “community substrates” on plant leaf microbiota using convergently evolved plant traits and specific microbial colonizers.
