Image copyright Yale University

US scientists say they have taken the first step towards making "safer" GMOs that cannot spread in the wild, using synthetic biology.

They have re-written the genetic code of bacteria to use only synthetic chemicals to grow.

The GM bacteria would die if they escaped into nature.

The research, published in Nature, is proof of concept for a new generation of GMOs, including plants, say Harvard and Yale university experts.

Genetically engineered micro-organisms are used in Europe, the US and China to produce drugs or fuels under contained industrial conditions.

I can see no need for this in crop plants that are anyway risk-assessed and approved for field cultivation, and use in food and feed Prof Huw Jones, Rothamsted Research

Scientists want to build in safety measures so that their spread could be controlled if they were ever used in the outside world, perhaps to mop up oil spills or to improve human health.

"What we've done is engineered organisms so that they require synthetic amino acids for survival or for life," Prof Farren Isaacs of Yale University, who led one of two studies, told BBC News.

He said the future challenge was to re-engineer the code of other lifeforms.

"What we're seeing here is an important proof of concept that re-coding genomes and engineering dependence on synthetic amino acids is technically feasible in not just E coli but other micro-organisms and multicellular organisms such as plants."

Containment

GMOs have a number of potential practical uses, including the production of drugs and fuels, and removing pollutants from contaminated areas.

However, strict containment measures would be needed to use them in open spaces to stop them spreading in the wild.

The US researchers describe their research, published in Nature journal, as a "milestone" in synthetic biology.

Prof George Church of Harvard Medical School, who led the other study, said in order to protect natural ecosystems and address public concern the scientific community needed to develop robust biocontainment mechanisms for GMOs.

"This work provides a foundation for safer GMOs that are isolated from natural ecosystems by a reliance on synthetic metabolites."

Image copyright AFP Image caption Maize: The research may have applications in plants, say the scientists

In both studies, the organisms cannot use alternative nutrients when synthetic amino acids are unavailable. They are also less likely to pass on their genes to other micro-organisms.

Ethics

Commenting on the study, Prof Huw Jones of Rothamsted Research in Hertfordshire, which carries out research on GM plants, said these were research-stage ideas to prevent the unintended spread of GM microbes from contained industrial units.

"I can see no need for this in crop plants that are anyway risk-assessed and approved for field cultivation, and use in food and feed," he said.

Prof Julian Savulescu, an ethicist at the University of Oxford, said the research would make GMOs and synthetic organisms safer as they would need to be fed special food (synthetic amino acids) to survive.

"But you can never remove all risk," he added. "There is still the very small chance of some natural event enabling them to change so as to be able to survive in the wild."

John Love, professor of Synthetic Biology at the University of Exeter, said it raised a lot of issues for society.

"It's a great technological leap but peripheral issues would need to be addressed to allay potential public concerns."

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