Scientists reprogrammed the common bacterium E. coli so it requires a synthetic amino acid to live. BSIP/UIG via Getty Images hide caption

Scientists reprogrammed the common bacterium E. coli so it requires a synthetic amino acid to live.

Researchers at Harvard and Yale have used some extreme gene-manipulation tools to engineer safety features into designer organisms.

This work goes far beyond traditional genetic engineering, which involves moving a gene from one organism to another. In this case, they're actually rewriting the language of genetics.

The goal is to make modified organisms safer to use, and also to protect them against viruses that can wreak havoc on pharmaceutical production.

To understand what they've done, you may need to remember a bit of basic biology. The enzymes and other proteins in our bodies are all built from building blocks called amino acids. There are usually just 20 amino acids in nature. But George Church, a professor of genetics at Harvard Medical School, has created a bacterium that requires an additional amino acid, one made in the lab and not found in nature. His lab did that by rewriting the bacteria's genetic language to add a "word" that calls for this unnatural amino acid.

"So this really makes it a completely new branch of life," Church says.

These modified E. coli bacteria essentially speak a different genetic language from all other life on Earth. That means they can't easily swap genes, which bacteria often do to pick up or get rid of traits. And it also means that these modified E. coli must be fed the synthetic amino acid to survive.

"It will die as soon as you remove that essential nutrient," Church says.

The scientists say this radical re-engineering actually makes these synthetic life forms safer, because if they escape into the wild they'll die. One key question is whether these engineered bacteria can shed the traits that make them dependent on the synthetic amino acid. (Bacteria mutate all the time, picking up new traits and dropping others).

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Scientists Give Genetically Modified Organisms A Safety Switch