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Transplanting circadian rhythms from one organism to another

It’s possible to transplant a heart, hands, even a face. But a circadian rhythm? It would seem hard even to know where to start.

A team of molecular biologists at Harvard Medical School (HMS) has accomplished the feat, however. Not in humans, though it would be nice one day to be able to reset a jet-lagged biological clock with a pill. Instead, they achieved it using the lowly cyanobacteria, which lives in the ocean, harvests light from the sun, and is one of the most simplistic organisms to operate on a 24-hour clock.

The experiment, published earlier this month in Science Advances, was conducted by graduate student Anna Chen working with Pamela Silver, an HMS professor and leading figure in the field of synthetic biology. It builds on work by a team of Japanese scientists who earlier identified three key genes that allow cyanobacteria to live in circadian fashion. Every 24 hours enzymes attach and then detach an element called a phosphate to a protein, which triggers time-sensitive behavior changes.


Chen and Silver inserted those genes into E. coli, which does not have a circadian rhythm. In order to monitor whether the circadian genes took, Chen engineered a system such that the E. coli would produce fluorescent proteins whenever their newly transplanted circadian clocks were working. If the flouorescent proteins were visible, they’d know the clock was running — and in most of the treated E. coli cells it was, for periods as long as three days.

“Anna interfaced the clock with transcription of genes that makes these colored proteins,” says Silver. “You could just look at cells and see that they were keeping time.”

Time-keeping is essential for human activity. It’s equally important in the rapidly growing field of synthetic biology, which seeks to engineer organisms to perform specific tasks. It’s understood, for instance, that certain diseases come on more strongly during certain times of the day. Time-keeping bacteria could be combined with antibiotics, or other forms of biological medicine, to release drugs at the specific times in the circadian cycle when they’re needed most.


Then, of course, there’s jet lag. At the time we talked, Silver had just returned to Boston from California and was still struggling with the time change. She mentioned that there’d been a study awhile back in which researchers implanted fecal matter from jet-lagged humans in normal rodents, after which the rodents started to act jet-lagged themselves. It was a fairly speculative result, though it does suggest the possibility that, sometime in the future, we could have whole new set of (slightly distasteful) rituals whenever we step off a plane in a distant city.

Kevin Hartnett is a writer in South Carolina. He can be reached at kshartnett18@gmail.com.