MEASURING THE HEALTH OF SOIL MICROBES USING BIO-ELECTROCHEMICAL SYSTEMS

Plant growth and other ecosystem functions depend on a complex interplay of phenomena that together determine soil health. Soil microbial activity underlies soil health, and therefore is a crucial metric and indicator of this phenomena. Despite its keystone relevance to soil function, existing approaches to query soil microbial activity are onerous, expensive, time consuming, often destructive, do not provide real time and time-resolved data, and are not readily amenable to field deployment over long time periods.We believe that it should be possible to capture a view of microbial activity states that provides insight into the (in)action of critical processes in healthy soils across space, strata, and time. The key insight is that the activity of exoelectrogenic bacteria that are ubiquitous in the soil microbiome is sensitive to critical processes such as carbon and nutrient cycling, and that electron transfer from bacterial activity can be observed and reported by carefully designed sensor systems. Our long-term vision is to design and deployment of novel sensors which are able to assess electrogenic microbial activity and to affix these new microbial sensors in conjunction with traditional sensors to an in situ energy-scavenging sensor platform to collect a three-dimensional sampling of microbial activity. To further that, this seed proposal targets two proof-of-concept elements that we deem essential first steps: 1.) the demonstration of a robust link between soil microbial activity (e.g., respiration, key enzyme activity) and electrical output, and 2.) the reliable measurement of what are anticipated to be small signals in the soil environment. This seed proposal targets two proof-of-concept elements that we deem essential:Task 1, the demonstration of a robust link between soil microbial activity (e.g.,respiration, key enzyme activity) and electrical output, and Task 2, the reliable measurement of what are anticipated to be small signals in the soil environment. Simultaneous research on these two elements is required to drive the convergence of the technologies.Research Questions and Outcomes• RQ1: Can we use bioelectrochemical signals as a proxy for microbial activity in soil? If so, what are the constraints?• RQ2: How do environmental factors such as moisture and temperature affect measurement accuracy?