The repressilator, a genetic circuit of three genes repressing each other to create oscillatory behavior, was one of synthetic biology’s earliest breakthroughs, showcasing the ability to engineer complex gene regulatory networks. Twenty-five years later, synthetic oscillators continue to fascinate.

In this talk, I will first present our work on developing a CRISPR-based repressilator—the "CRISPRlator"—in Escherichia coli and its application in Streptococcus pneumoniae to control capsule production, yielding the "CAPSUlator", as well as its use in a light biosensor. I will then introduce the "Optoscillator," an optogenetic version of the repressilator. Analogous to a clock and wavefront mechanism, in a growing bacterial colony harbouring the repressilator, the periodic oscillations are transformed into spatial ring patterns. We analysed the rings when the cells were subjected to different regimes of light exposure. By combining experiments with mathematical modelling, we demonstrated that this simple circuit can exhibit complex dynamics under external periodic forcing, including synchronization, resonance, period doubling, period-4 behaviour, and even chaos. I will conclude with our ongoing efforts to study coupled synthetic oscillators and expand into multicellular consortia.

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