Taking one step forward toward designing synthetic life, researchers have assembled the first cells that can count. A team from Harvard, MIT and Boston University mounted two different gene networks inside E. coli that helped the bacterial cells count up to three biochemical processes.
The study, published in the May 29 Science, achieves an elusive goal in the field of synthetic biology, which attempts to assemble cells and bacteria with programmed behaviors. The technique is still in its very early stages, but it holds promise for a vast range of uses including drug production, toxin detection and environmental cleanup. Timothy Lu, an MD–PhD student in the Harvard–MIT Division of Health Sciences and Technology, and Ari Friedland, a graduate student at Boston University, are lead authors of the study. Co-authors include George Church, HMS professor of genetics, and James Collins, professor of biomedical engineering at BU, both members of Harvard’s Wyss Institute.
The researchers developed two different counters based on dominolike gene processes that ended with the production of a fluorescent protein. Each successive tick of the counter was induced by arabinose, a kind of sugar that moved gene transcription one step forward at a time when injected into the cell. Both models were first tweaked to send their fluorescent signal when two steps were completed. Then they were extended to send the signal after a three-step reaction. One of the counters proved more effective at accounting for events happening within short time spans while the other was able to detect changes within a period of up to 12 hours. The latter counter was also able to store its state in memory based on DNA orientation within the genetic network and be activated with three different inducer molecules, the researchers said.
The first counter might be used to program cell death once a specific number of cell divisions had taken place, which would be useful as a safety measure to control new treatment and diagnostic applications. The second counter might be programmed to count day–night cycles and track genetic chain reactions in the study of organism development.
Students may contact James Collins at jcollins@bu.edu for more information.
