ENGINEERING PSEUDOMONAS STUTZERI AS A BIOGEOCHEMICAL BIOSENSOR

Biogeochemical cycles are being drastically altered as a result of anthropogenic activities, such as the burning of fossil fuels and the Haber-Bosch process. We know microbes play a major part in these cycles, but the extent of their biogeochemical roles remains largely uncharacterized due to inadequacies in culturing and measurement. While metagenomics and other –omics methods offer ways to reconstruct microbial communities, these approaches can only give an indication of the functional roles of microbes in a community. These –omics approaches are rapidly being expanded to the point of outpacing our knowledge of functional genes, which highlights an inherent need for analytical methods that non-invasively monitor Earth’s processes in real time.

Here we aim to exploit synthetic biology methods in order to engineer a ubiquitous denitrifying microbe, Pseudomonas stutzeri, that can act as a biosensor in soil and marine environments. By using an easily cultivated microbe that is also common in many environments, we hope to develop a tool that allows us to zoom in on specific aspects of the nitrogen cycle. In order to monitor what’s going on at the genetic level in environments that cannot be resolved with fluorescence-based methods, we have developed a system that instead relies on gas production by these microbial biosensors.

P. stutzeri has been successfully engineered to release a gas, methyl bromide, which can continuously and non-invasively be measured by GC-MS. The gene controlling gas production can be linked to those involved in denitrification, thereby creating a quantifiable gas signal that is correlated with microbial activity. Synthetically engineered microbial biosensors could reveal key aspects of metabolism in soil systems and offer a tool for characterizing the scope and degree of microbial impact on major biogeochemical cycles.