Special Bioengineering Seminar

 Abstract:  Circadian oscillators maintain a constant period over a wide range of ambient temperatures. Although such temperature compensation has long been known, the mechanisms that regulate the effect are poorly understood. Natively occurring circadian oscillators are inherently complex and difficult to study in vivo. Thus, simple, synthetically constructed gene circuits are an attractive alternative for investigating non-trivial dynamics and robust behaviors in biological networks. In this talk, I will describe the design and construction of a synthetic gene oscillator in Escherichia coli that exhibits robust temperature compensation. The design is based on a previously described synthetic oscillator consisting of linked positive and negative transcriptional feedback loops. Computational modeling predicted and subsequent experiments confirmed that a single amino acid mutation to the transcriptional repressor within the circuit produces temperature compensation in the oscillator. Specifically, we used a temperature-sensitive lactose repressor mutant that loses the ability to repress its target promoter at high temperatures. In the oscillator, this thermo-induction of the repressor leads to an increase in oscillation period at high temperatures that compensates for the decrease in period due to Arrhenius scaling of the reaction rates. The result is a genetic oscillator whose period is roughly 48 min for temperatures ranging from 30⁰ C to 41⁰ C. This work demonstrates that dynamic synthetic gene circuits can be engineered to be robust to extracellular conditions.