By Kari Lydersen in Discover Magazine
As genetically-modified microbes
take on ever more tasks – from creating new pharmaceuticals to turning out
clean fuel sources – researchers have searched for a way to biologically
isolate them from their wild counterparts, so that if they were ever
accidentally released, they wouldn’t be able to survive.
Now, scientists releasing two separate papers in the journal Nature think they
have a solution. They unveiled two different approaches to modifying a strain
of E. coli to make it dependent on artificial nutrients. In a
controlled environment, such as a research lab or factory, scientists would
provide that sustenance. But if the bacteria break free, they wouldn’t be able
to make the compounds themselves, and would die.
No
Escape
Scientists have previously used
similar approaches, making GMO bacteria reliant on synthetic nutrients. But in
the past, the GMO bacteria have evolved the ability to live without the
synthetic nutrients. Bacteria have ejected the part of their DNA that made them
reliant on the nutrients, or they figured out how to cobble together an
equivalent of those nutrients from the natural world.
In separate projects, teams led by
Yale molecular biologist Farren Isaacs and Harvard molecular geneticist George
Church have genetically modified E. coli so that it is totally dependent
on synthetic amino acids. And in both cases that need is built in to multiple
parts of the bacteria’s genome – 49 times in the Harvard study – so that the
likelihood that the bacteria would evolve to overcome the restriction is
unlikely. And both strains showed an undetectably small escape rate – the
number of E. coli able to survive without being fed the synthetic amino
acid.
Out
in the Open
Church and Isaacs said that their
work is most likely to be used in pharmaceutical or dairy operations – making
cheese, yogurt or drugs. These processes happen in closed facilities and
fermenters. Unlike in the fields, bees or breezes won’t spread genetically
modified material around, but there is a risk of contamination if the
microscopic bacteria get onto employees’ clothing or into the air.
Meanwhile the scientists hope their
research lays the groundwork for larger applications of modified bacteria in
open-air settings, including for bioremediation – the use of living organisms
to clean up polluted sites like landfills and oil spills. In these settings a
reliance on synthetic amino acids mean the genetically modified organisms could
be “contained” molecularly even if they are no longer physically contained.
Future
Uses
The safety features aren’t the only
appealing attribute of the modified E. coli featured in the new
papers. The scientists also built in resistance to a number of viruses. That
means the bacteria are safe from attack by viruses that can be devastating in
food or pharmaceutical manufacturing – like when viral contamination caused a Genzyme Corp. plant to halt manufacturing in 2009,
temporarily cutting off the medication supply for some patients.
Church noted that the viral
resistance could be an incentive to “sweeten the offer” and encourage companies
to use “safe” GMOs. The technique could also provide intellectual property
protection for industrial, pharmaceutical or food companies, since they could
make their own GMOs dependent on specific synthetic amino acids, and other
companies would have trouble replicating those modified organisms without the
“key.” Such built-in IP protection could actually encourage collaboration
between different companies, Isaacs said.
“This is really motivated by
anticipating the impact biotechnology will have over the next several decades,
recognizing the importance of endowing these GMOs with more sophisticated
functions, to have more safety measures going forward,” Isaacs told reporters.
“Endowing safeguards will be important to allow the field to progress.”
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