Bacteria circadian clock protein molecule. Computer model showing the molecular structure of the KaiC protein found in cyanobacteria (blue-green algae). KaiC is a protein expressed by the kaiC gene and is one of three such proteins that are essential for circadian rhythms in these bacteria. Circadian rhythms are biological 'clocks' with a period close to 24 hours in duration that help regulate sleeping and feeding patterns in animals. In bacteria, they are thought to help regulate cell division.