In a bid to reduce the risk of genetically modified organisms escaping into the environment and disturbing natural ecosystems, two groups of scientists in the U.S. have rewritten the genetic code of bacteria to produce strains that are totally dependent on unnatural substances to grow.
Not only do these organisms die without their synthetic food, but they are also resistant to viruses and unable to exchange their engineered DNA with natural counterparts. Although the techniques have only been used on bacteria so far, the researchers believe it may be possible to extend them for more complex organisms, such as plants. Both of the studies can be found in the journal Nature.
With advances in the fields of synthetic and molecular biology, genetically modified organisms (GMOs) have rapidly emerged as valuable solutions in a variety of clinical, industrial and environmental settings. They’re already widely used to improve agriculture, produce biofuels and pharmaceuticals, and to help clean up the environment. But while they are proving to be invaluable tools to today’s society, it is well recognized that these organisms could pose a risk to natural ecosystems if they escape and proliferate uncontrollably.
In order to prevent this from happening, and to address public concern, scientists need to develop robust biocontainment strategies. One method that researchers have been exploring involves tweaking bacteria so that they are unable to produce certain nutrients necessary for growth. The problem with this is that the organisms tend to be able to scavenge these foods from the environment, or evolve pathways to synthesize them. Alternatively, they could exchange genes with others and acquire the ability to make them. Scientists therefore need to come up with novel techniques that circumvent these issues, and two new studies demonstrate that significant progress has now been made toward “safer” GMOs.
Although the studies were independent, both went for the same strategy, but they adopted different methods to produce their organisms. The work builds on a previous study in which the researchers radically altered the genome of the bacterium E. coli, producing the world’s first genomically recoded organism. Both groups then went on to further engineer this microbe so that it is totally reliant on an amino acid—a building block of proteins—that is not found in nature. Without this synthetic supplement, the organisms can no longer synthesize everything they need to live.
Importantly, the researchers targeted genes that are critical for survival, and also made a large number of alterations, meaning it would be very difficult for the organism to evolve mechanisms to live without the artificial food. Furthermore, because the genetic code is so vastly different to that of natural counterparts, the risk of exchanging DNA with other organisms in the environment is virtually eliminated.
The microbes were so dependent on the unnatural amino acid that even after growing billions of the cells in numerous experiments, the researchers couldn’t detect a single organism that was capable of surviving without the synthetic food. “Our strains, to the extent that we can test them, won’t escape,” says study author Dan Mandell.
While the researchers have only tested out this technique on bacteria, it may be possible to modify it for use in other organisms, such as plants and animals.