Studies using cell-based systems and genetic techniques have identified the molecular mechanisms that establish and maintain cellular clocks.

The exact timing of this rhythm is established via cell-autonomous oscillators called cellular clocks, which are controlled by transcription/ translation-based negative feedback loops. Under natural conditions, organisms are trained to follow a 24-h cycle under environmental time cues such as light to maximize their physiological efficiency. Furthermore, the clock is obvious in a standard, haploid, auxotrophic strain, opening the door for rapid progress into cellular clock mechanisms.Ĭircadian clocks are intrinsic, time-tracking systems that bestow upon organisms a survival advantage. Our results show that metabolism in yeast shows systematic circadian entrainment, responding to cycle length and zeitgeber (stimulus) strength, and a (heavily damped) free running rhythm. Here, we use continuous cultures of yeast, establishing conditions that reveal characteristic clock properties similar to those described in other species. Although Saccharomyces cerevisiae is among the most powerful genetic experimental systems and, as such, could greatly contribute to our understanding of cellular timing, it still remains absent from the repertoire of circadian model organisms. The molecular mechanism of circadian clocks has been sketched out in genetic model systems from prokaryotes to humans, revealing a combination of transcriptional and posttranscriptional pathways, but the clock mechanism is far from solved.

The biological clocks that orchestrate these daily changes confer a survival advantage and dominate daily behavior, for example, waking us in the morning and helping us to sleep at night. Circadian clocks organize gene expression, metabolism, and behavior such that they occur at specific times of day. Circadian timing is a fundamental biological process, underlying cellular physiology in animals, plants, fungi, and cyanobacteria.

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