Ever had jet-lag? This woe of long-distance travelers strikes when your circadian rhythm
(or, biological clock) is misregulated. Circadian rhythms have been observed in numerous animals, plants, and fungi. What about bacteria, you ask? Why yes, some bacteria even have a biological clock!
In animals (humans included) body temperature, hormone production, and brain waves all follow circadian rhythms. In fact, when certain “clock” genes are mutated in mice, the animals become obese and are no longer able to regulate glucose metabolism. Basically, the biological clock is a pretty big deal.
Recently, Harvard University researchers “transplanted” a biological clock into E. coli
, a species of bacteria that doesn’t naturally follow circadian rhythms. They did so by outfitting E. coli
with a circadian rhythm-controlled “protein circuit” from the cyanobacterium Synechoccus elongatus
This protein circuit is made up of three major proteins: KaiA, B, and C. During the day, KaiA promotes the phosphorylation of KaiC
. At night, KaiB inhibits KaiA, causing KaiC to be dephosphorylated. Certain genes, like those important for cell division and photosynthesis, are regulated based on whether or not KaiC is phosphorylated. The researchers also hooked this protein circuit up to a reporter system that produced an easily-detectable fluorescent protein based on whether or not KaiC was phosphorylated.
Pretty cool, but what’s the point? Bacteria engineered to respond to circadian rhythms could be used to release drugs or other therapeutics over a specific time frame. According to study author Anna Chen, “the ultimate dream application would be to deliver these circadian E. coli
to an individual in pill form, which could allow the circadian rhythm to be linked to additional biological circuits in order to perform a precisely–timed release of drugs, or to be able to sense and influence the host's circadian rhythm”.
, Harvard University