Bacteria have been programmed like a computer to produce colored patterns by communicating with each other.

The bacteria, E. coli, were programmed to emit red or green fluorescent light in response to signals from other E. coli.

In one experiment, they glowed green in high concentrations of a signal chemical and red in low, forming a bull’s-eye pattern in a Petri dish.

“We are really moving beyond the ability to program individual cells to programming a large collection—millions or billions—of cells to do interesting things,” says researcher Ron Weiss of Princeton University.

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