(February 29, 2016) Duke
University bioengineers design cells that die if they leave the confines of
their capsule
Duke University researchers have engineered microbes that
can’t run away from home; those that do will quickly die without protective
proteins produced by their peers.
Dubbed “swarmbots” for their ability to survive in a crowd,
the system could be used as a safeguard to stop genetically modified organisms
from escaping into the surrounding environment. The approach could also be used
to reliably program colonies of bacteria to respond to changes in their
surrounding environment, such as releasing specific molecules on cue.
The system is described online February 29, 2016, in
Molecular Systems Biology.
“Safety has always been a concern when modifying bacteria
for medical applications because of the danger of uncontrolled proliferation,”
said Lingchong You, the Paul Ruffin Scarborough Associate Professor of
Engineering at Duke University.
“Other labs have addressed this issue by making cells rely
on unnatural amino acids for survival or by introducing a ‘kill switch’ that is
activated by some chemical,” You said. “Ours is the first example that uses
collective survival as a way of intrinsically realizing this safeguard.”
In the experiment, You and his colleagues engineered a
non-pathogenic strain of E. coli to produce a chemical called AHL. They also
modified the cells so that, in high enough concentrations, AHL causes them to
produce an antidote to antibiotics. When the population of E. coli is dense
enough, the antidote keeps them alive, even in the presence of antibiotics that
would otherwise kill them.
The researchers then confined a sufficiently large number of
the bacteria to a capsule and bathed it in antibiotics. As long as the E. coli
remained inside their container where their density was high, they all
survived. But if individual bacteria escaped, they were quickly killed off by
the antibiotic.