Imagine a diabetic with specially engineered cells that detect the rise and fall of his or her blood sugar and administer insulin if needed. Imagine cancer patients intentionally infected with a "smart virus" that can determine if cells are cancerous and then destroy the dangerous cell from the inside. And imagine cells engineered to excrete biofuels or pharmaceutical products.

These are the visions of synthetic biology. A relatively new breed of researchers, synthetic biologists view the future through a lens in which specially designed DNA sequences, proteins and cells do the work of creating compounds, elements and biological materials that help us treat diseases, produce new kinds of medicines and even establish colonies on other planets.

"The big breakthrough 100 years ago was organic chemistry, when people figured out how to make synthetic materials," says Harvard University biologist Pamela Silver. But "a cell is probably an even better chemist."

The concepts behind synthetic biology have since at the least the 1970s, when scientists inserted the genes to make human insulin into E. coli bacteria, but the outcomes of experiments were notably hit and miss. That's changing quickly.

"Now we're coming to a point where, when I say this part does something, other designers can trust it," said Adam Arkin, a professor of engineering and the director of the University of California at Berkeley's synthetic biology institute.

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One project Silver and her colleagues at Harvard are working on is building human and other mammalian cells that can record and remember past events and also be able to "count" forward in time. Such clocked cells would be useful as sensors and could also be part of a new wave of intelligent therapeutics, remembering how a patient's body reacted to previous treatments.

Another project, backed by the U.S. Department of Energy, is a genetically engineered bacteria named Shewanella.Silver and her team are trying to rejigger the bacteria's photosynthetic pathways so it will accept electricity instead of light as an energy source, an advance that would allow biofuel-excreting microorganisms to be plugged into the grid. The Harvard team is also trying to engineer Shewanella to generate fuel that's similar to diesel fuel or gasoline and which requires no additional chemical processing after being pumped out of the bacteria-filled tank.

"It's a very 'blue sky'-type project," Silver says, meaning that Shewanella's success is uncertain.

Synthetic biology's arrival on the scene coincided with the first International Genetically Engineered Machine competition in 2004, in which five teams worked on building their own biological systems. In that initial competition, a team from the University of Texas at Austin created a bacterial photographic "film" using color-changing bacteria that responded to light input. One image captured on this film was two lines of text: "Hello World."

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Synthetic Biology Turns Cells Into Chemists Producing Treatments For Diabetes And Cancer -- And Easing Journeys To Mars