Certain strains of the E. coli bacterium have gotten some bad press lately. Yet this much-maligned species may have some medically beneficial biotechnological uses after all.
Researchers at Cellicon Biotechnologies, Boston, Mass., have constructed a genetic flip-flop (toggle switch) and clock, the first building blocks of a biological state machine. In the flip-flop, two DNA elements and their regulator genes are arranged in E. coli samples so each gene inhibits the synthesis of the other. Either gene can be produced at a given time, but both cannot be synthesized simultaneously.
The genetic flip-flop is analogous to the set and reset of an electronic RS latch. Likewise, the genetic clock consists of three regulator genes and their associated DNA elements arranged sequentially in a negative-feedback loop in the bacterium. When the three genes are engineered with appropriate kinetic energies, the biological circuit, or genetic applet, produces an oscillatory gene expression.
Before biological circuits become practical, efficient and scalable ways to fabricate long sequences of DNA must be developed. Binding these sequences in a desired circuit is another challenge. Though these biological applets cannot replace electronic circuits, they will fill biochemical needs at cellular levels.
Timothy S. Gardner presented Cellicon's work at the recent International Solid State Circuits Conference. For more information, go to www.cellicon.com.