Researchers at UC Merced have demonstrated that artificial cells can maintain a regular 24-hour rhythm, similar to the circadian clocks found in living organisms. The study, published in Nature Communications, was led by bioengineering professor Anand Bala Subramaniam and chemistry and biochemistry professor Andy LiWang. Alexander Zhang Tu Li, who completed his Ph.D. in Subramaniam’s lab, served as the first author.
The team investigated how biological clocks function by reconstructing the clockwork of cyanobacteria within vesicles—simplified structures resembling cells. These vesicles contained core clock proteins, with one protein tagged using a fluorescent marker to monitor activity.
Over four days, the artificial cells displayed a rhythmic glow every 24 hours. When researchers reduced the number of clock proteins or made the vesicles smaller, this rhythmic pattern disappeared in a predictable way.
To interpret these results, the researchers developed a computational model. Their analysis indicated that higher concentrations of clock proteins make the clocks more robust and allow many vesicles to keep time reliably even if there are small differences in protein levels between them. The model also suggested that while another component of natural circadian systems is not essential for individual clocks to function, it is important for synchronizing timing across groups of cells.
The study further observed that some clock proteins adhere to the walls of vesicles, requiring higher total protein amounts for proper operation.
“This study shows that we can dissect and understand the core principles of biological timekeeping using simplified, synthetic systems,” said Subramaniam.
Mingxu Fang, a microbiology professor at Ohio State University who specializes in circadian clocks, commented on the significance of this work: “The cyanobacterial circadian clock relies on slow biochemical reactions that are inherently noisy, and it has been proposed that high clock protein numbers are needed to buffer this noise. This new study introduces a method to observe reconstituted clock reactions within size-adjustable vesicles that mimic cellular dimensions. This powerful tool enables direct testing of how and why organisms with different cell sizes may adopt distinct timing strategies, thereby deepening our understanding of biological timekeeping mechanisms across life forms.”
Subramaniam is part of UC Merced’s Department of Bioengineering and affiliated with its Health Sciences Research Institute (HSRI). LiWang belongs to the Department of Chemistry and Biochemistry and is also an HSRI affiliate. He has been recognized as a fellow by the American Academy of Microbiology and will receive the Dorothy Crowfoot Hodgkin Award from The Protein Society in 2025.
Funding for this research came from several sources: Subramaniam’s National Science Foundation CAREER award from the Division of Materials Research; grants from both the National Institutes of Health and Army Research Office awarded to LiWang; and an NSF CREST Center fellowship supporting LiWang at UC Merced.
