The circadian clock represents a fundamental aspect of biology that is possibly common to all cells. The clock imposes a temporal structure on processes from gene expression to behavior. Although circadian clocks are recognised in the lab by a self-sustained, approximately 24h oscillation in constant conditions, these clocks are virtually always found in the entrained state in nature. Entrainment is the process whereby the circadian machinery is stably synchronized to the 24h environmental cycle. Zeitgebers, the stimuli that reliably recur each 24h, include light and numerous other predictable features of the environment stemming from the light cycle (e.g. temperature, food, etc.). Due to biological, genetic and environmental variability (e.g. season), a distribution of entrained phases or chronotypes is observed in a given population. Thus, entrainment is not a single entity but rather a dynamic process and until we have figured out the rules therein we cannot understand daily timing.
We like entrainment as an experimental tool and we use it a lot! Our main project at this point involves circadian clocks in non-photosynthetic bacteria. We operate from the hypothesis that all terrestrial organisms will have a circadian clock, a mechanism to keep track of time of day. We recognize the non-photosynthetic bacteria as an important frontier in the search for circadian clocks. We are attempting to unlock the secrets of the circadian clock in this huge class of organisms, using B. subtilis and E. coli in major efforts at this time.
Institute of Medical Psychology