SPIES AND BLOGGERS: NEW SYNTHETIC BIOLOGY TOOLS TO UNDERSTAND MICROBIAL PROCESSES IN THE EARTH SYSTEM

Microbes can be programmed via synthetic biology to report on their behavior, informing researchers when they have participated in key biogeochemical processes (e.g. denitrification) or when their immediate environment has passed a particular physical threshold (e.g., a microbial-scale change in soil water conditions). This use of synthetic biology has the potential to significantly improve our understanding of microbes’ roles in elemental and water cycling. However, synthetic microbes have not yet seen wide laboratory use in geobiology because synthetic organisms typically report by fluorescing, making their signals difficult to detect outside the petri dish. We are developing a new suite of microbial programs that report instead by releasing easily-detected gases, allowing the real-time, noninvasive monitoring of behaviors in sediments and soils. Microbial biosensors can, in theory, be programmed to detect dynamic processes that contribute to a wide range of geobiological processes, including C cycling (biofilm production, methanogenesis, and synthesis of extracellular enzymes that degrade organic matter), N cycling (expression of enzymes that underlie different steps of the N cycle) and potentially S cycling.

We will provide an overview of the potential uses of gas-reporting biosensors in the Earth system and will report the development of the systematics of these sensors. Successful development of gas biosensors for laboratory study of soils and sediments will require addressing issues including: engineering the intensity and selectivity of microbial gas production to maximize the signal to noise ratio; normalizing the gas reporter signal to cell population size, managing gas diffusion effects on signal shape; and developing multiple gases that can be used in parallel.