Researchers Engineer ‘Kill Switches’ Into GMOs To Keep Them From Escaping Into The Environment | Chemical & Engineering News
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Web Date: December 10, 2015

Researchers Engineer ‘Kill Switches’ Into GMOs To Keep Them From Escaping Into The Environment

Synthetic Biology: Two new gene circuits, called Passcode and Deadman, make it easy to destroy genetically modified bacteria when their job is done
Department: Science & Technology
News Channels: Biological SCENE, Environmental SCENE
Keywords: GMO, biocontainment

Genetically modified bacteria are widely used in the biotech industry to make products as diverse as yogurt and fine chemicals. But before these genetically modified organisms can be put to work outside the laboratory or factory—for example, in the human gut as probiotics—researchers need to develop reliable ways to keep them on a leash and kill them once their job is done.

A team led by Massachusetts Institute of Technology’s James J. Collins now reports two new biocontainment strategies, called kill switches, that prevent GMOs from running amuck in the environment. These new gene circuits, which are easier to use and modify than prior GMO kill switches, make it impossible for a genetically modified bacterium to survive unless it receives a specific chemical or combination of chemicals provided externally (Nature Chem. Biol. 2015, DOI: 10.1038/nchembio.1979).

To make the first circuit, dubbed Deadman, Collins and his team engineered Escherichia coli and Pseudomonas putida to have genes that code for a deadly toxin. They also engineered the bacteria so that the presence of a specific chemical, such as anhydrotetracycline, blocks expression of the toxin-producing genes. Take away the external chemical—which ideally is so unusual that the bacteria cannot scavenge it from the environment—and the GMO makes the toxin and dies.

To make the second circuit, nicknamed Passcode, the team programmed bacteria to rely on the presence or absence of a cocktail of three chemicals for survival. If the bacteria receive the right combination of chemicals—the correct “passcode”—then they do not activate their kill switch. The team demonstrated the concept by engineering E. coli so that if the bacteria are exposed to isopropyl β-D-1-thiogalactopyranoside, and at the same time, they don’t have access to cellobiose or galactose, then they die.

“These synthetic gene circuits efficiently kill E. coli and can be readily reprogrammed to change their environmental inputs, regulatory architecture and killing mechanisms,” the team notes. The Passcode biocontainment circuit could also be used for intellectual property protection, the researchers suggest, because nobody but the GMO’s engineer would know the combination of chemicals that allow it to grow.

“This is an exciting paper because of the modularity and ease of use,” of the new kill switches, comments Guy Bart Stan at Imperial College London. “The barrier of implementation is low,” he adds, which could allow researchers “to improve the level of biocontainment in the here and now.” Stan cautions, though, that “there is no GMO biocontainment solution at the moment that is 100% fail-safe.”

 
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Comments
Chauncey M. DePree, Jr. (December 10, 2015 9:04 PM)
Genetic research is not something we can stop. The question is how we deal with the inevitable results. Novels help us sort through the many consequences of genetic research, good, bad, and in between. Consider "TobaccoPharm": If you had knowledge to end addiction to tobacco, especially save future generations of children from the scourge of tobacco, would you use that knowledge? A scientist reported in “TobaccoPharm” has that knowledge and acts on it. http://www.amazon.com/Tobacco-Pharm-Trust-One…/…/ref=sr_1_1…

A new day dawned for tobacco. No longer did farmers have work in the industry of death. They had a choice. Dr. Karl Hauer learned to cultivate tobacco to produce valuable human proteins to fight the diseases that plague us. A research assistant, however, had a different plan. Lucian Reimann embedded a virulent carcinogen in the transgenic tobacco and released it into the environment, after he neutralized the "kill switches." He vowed to do what all the effete do-gooders couldn’t, or wouldn’t. The new tobacco became a decoy to destroy the cigarette industry. The first sudden deaths went unnoticed, lost in a sea of cigarette related diseases and misdiagnoses . . .

Marc
Chauncey M. DePree, Jr.
Xiaoyi Cao (December 13, 2015 2:04 AM)
There is an error in this report. The way it is written in the news now, "The team demonstrated the concept by engineering E. coli so that if the bacteria are exposed to isopropyl β-D-1-thiogalactopyranoside, and at the same time, they don’t have access to cellobiose or galactose, then they die." suggests that all three conditions (not exposed to IPTG, access to cellobiose, access to galactose) need to be violated before the bacteria die, which is not the case. According to Figure 3 in the paper, as long as one of the conditions are violated those bacteria will die.

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