Autonomous Oscillations in a Colloidal Fluid Driven by Cyanobacterial Circadian Rhythms

Cyanobacteria rely on a circadian oscillator system of proteins, KaiA, KaiB and KaiC, to regulate a variety of cellular processes. Powered by ATP phosphorylation, KaiA and KaiB proteins alternately bind to KaiC to produce periodic structural changes in KaiC. We repurpose this circadian system to design colloidal fluids with autonomous structural oscillations enabled by rhythmic crosslinking of colloids by KaiC-KaiB complexes. We show that the colloids can oscillate between liquid-like states, with individual colloids diffusing freely, to states in which colloids form large clusters with minimal motion, in sync with the binding cycles of KaiC and KaiB. We use differential dynamic microscopy (DDM) and spatial image autocorrelation analysis (SIA) to characterize the rhythmic dynamics and structure of the colloidal fluids and their dependence on the state of the Kai oscillator. Our findings demonstrate that a cyanobacterial circadian oscillator can drive autonomous alterations in abiotic colloidal materials, with applications in next-generation drug delivery, filtration, and infrastructure repair. Our results further equip researchers with new biochemical machinery for developing self-directed, programmable, and reconfigurable biomaterials.