Synthetic biology allows researchers to program cells to perform novel functions such as fluorescing in response to a particular chemical or producing drugs in response to disease markers. In a step toward devising much more complex cellular circuits, MIT engineers have now programmed cells to remember and respond to a series of events. These cells can remember, in the correct order, up to three different inputs, but this approach should be scalable to incorporate many more stimuli, the researchers say. Using this system, scientists can track cellular events that occur in a particular order, create environmental sensors that store complex histories, or program cellular trajectories. This approach allows scientists to create biological "state machines"—devices that exist in different states depending on the identities and orders of inputs they receive. The researchers also created software that helps users design circuits that implement state machines with different behaviors, which can then be tested in cells. http://phys.org/news/2016-07-scientists-cells-series-stimuli.html
