演者：Carl Hirschie Johnson
Vanderbilt University, Nashville, USA
演題：As Time Glows By: Circadian Rhythms from Molecules to Populations
"Chronobiologists" study biological oscillators, the most prominent being circadian rhythms that are circa-24 h "clocks" that act as biological timekeepers to help organisms adapt optimally to the daily light/dark (and temperature) cycles that result from the earth's rotation. Twenty-five years ago, chronobiologists did not believe that prokaryotic organisms (aka bacteria) had circadian oscillators. This idée fixe was overturned by discoveries from our laboratory and others that demonstrated a bona fide circadian clock system in prokaryotic cyanobacteria (aka blue-green algae). Since that time, tremendous strides have been accomplished in our understanding of this bacterial clock system, which has remained at the forefront of circadian rhythm research. For example, the cyanobacterial system provided the first rigorous tests of the adaptive significance of circadian clocks. Moreover, the cyanobacterial clock proteins KaiA, KaiB, and KaiC were the first to have their crystal structures solved. Most remarkable was the first demonstration of a biochemical oscillator reconstituted from purified KaiA, KaiB, and KaiC proteins in vitro. In a fundamental sense eukaryotic clock systems may be organized very similarly to the cyanobacterial system, including multiple oscillators that are coupled to promote resilience. Moreover, the cyanobacterial circadian program regulates gene activity and metabolic pathways, and it can be manipulated to improve the expression of practically useful bioproducts (e.g., biofuels, biopharmaceuticals) using cyanobacteria as bioreactors. Finally, we are extending our studies on the adaptive value of circadian rhythms in cyanobacteria to other bacteria that have KaiB and KaiC genes to illuminate the steps by which biological clocks may have evolved.
世話人：理学系研究科 深田 吉孝