New Real-Time Approach for Monitoring Chemical Production by Genetically Engineered Microbes

Fluorescent sensors were developed to measure the productivity of bacteria engineered to synthesize precursors for plastics and other materials.

The Science

Metabolic engineering of microbes has great potential for sustainable and environmentally friendly production of industrial chemicals. Researchers at Harvard University have designed molecular tools (sensors) that enable them to follow the production of precursors for plastics and other chemicals in engineered microorganisms. These sensors produce increasing fluorescence as the amount of the desired product augments (i.e., “sensing” the presence of the product), making it possible to rapidly select the genetic modifications that result in the highest chemical yields.

The Impact

Constructing new microorganisms that make high amounts of desired compounds requires designing, modifying, and testing many different strains to ultimately select the best producer. Those tests use laborious and costly analytical techniques. The fluorescent sensors developed by this research enable rapid detection of individual strains that produce the largest amounts of desired chemicals by just measuring fluorescence. Coupled with cell sorting technologies, these sensors will enable the testing of millions of engineered strains in a single day.


This research has resulted in the development of a genetic sensor that provides a fluorescent readout proportional to the intracellular concentration of 3-hydroxypropionate, a valuable plastic precursor also called 3HP. This sensor required the introduction of several enzymes into the model bacterium Escherichia coli to convert 3HP into acrylate (another plastic precursor). Next, the gene for a fluorescent reporter whose expression is activated by acrylate also was introduced into the same E. coli strain so that when acrylate is produced, fluorescence can be detected and used as proxy for the amount of 3HP synthesized. With this system, the researchers could easily identify a strain and culture conditions that produced over 20 times more 3HP than previously achieved. At the same time, this research demonstrated the first heterologous pathway for microbial production of acrylate. The investigators proved the flexibility of the approach by designing a similar sensor to monitor muconate (used to make nylon) and glucarate (needed for manufacturing detergents and other chemicals). The fluorescent biosensors developed by this research combined with fluorescence-based cell sorting will accelerate the development of sustainable production of relevant chemicals such as biofuels and biopolymers in engineered microbial systems.

Principal Investigator(s)

George Church
Harvard University


This work was supported by the Office of Biological and Environmental Research within the U.S. Department of Energy’s Office of Science award DEFG02-02ER63445. Authors also acknowledge support from the National Science Foundation.


Rogers, J. K., and G. M. Church. 2016. “Genetically Encoded Sensors Enable Real-Time Observation of Metabolite Production,” Proceedings of the National Academy of Sciences (USA) 113(9), 2388-93. DOI: 10.1073/pnas.1600375113.