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Science 324 (5931): 1199-1202

Copyright © 2009 by the American Association for the Advancement of Science

Synthetic Gene Networks That Count

Ari E. Friedland,1,* Timothy K. Lu,1,2,* Xiao Wang,1 David Shi,1 George Church,2,3 James J. Collins1,{dagger}

Abstract: Synthetic gene networks can be constructed to emulate digital circuits and devices, giving one the ability to program and design cells with some of the principles of modern computing, such as counting. A cellular counter would enable complex synthetic programming and a variety of biotechnology applications. Here, we report two complementary synthetic genetic counters in Escherichia coli that can count up to three induction events: the first, a riboregulated transcriptional cascade, and the second, a recombinase-based cascade of memory units. These modular devices permit counting of varied user-defined inputs over a range of frequencies and can be expanded to count higher numbers.

1 Howard Hughes Medical Institute, Department of Biomedical Engineering, Center for BioDynamics and Center for Advanced Biotechnology, Boston University, Boston, MA 02215, USA.
2 Harvard-MIT Division of Health Sciences and Technology, 77 Massachusetts Avenue, Room E25-519, Cambridge, MA 02139, USA.
3 Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.

* These authors contributed equally to this work.

{dagger} To whom correspondence should be addressed. E-mail: jcollins{at}

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