Biology

MIT develops "passcode" and "deadman" kill switches to keep engineered bacteria in check

MIT develops "passcode" and "d...
The switches operate in a similar manner, killing off the host bacteria if the correct chemicals aren't present
The switches operate in a similar manner, killing off the host bacteria if the correct chemicals aren't present
View 1 Image
The switches operate in a similar manner, killing off the host bacteria if the correct chemicals aren't present
1/1
The switches operate in a similar manner, killing off the host bacteria if the correct chemicals aren't present

A team of MIT scientists has created apair of mechanisms designed to provide a fail-safe for geneticallymodified bacteria, with the aim of stopping them from escaping andproliferating outside their intended environment. The measure wouldmake the engineered bacteria much safer.

Genetically-engineered bacteria couldone day be used for all sort of things, from monitoring toxins inwater sources to moving around the human body to diagnose and treatinfections. But in order for widespread use to be viable, it's firstessential that measures are put in place to shut down the bacteria,should they start behaving in an undesirable manner.

A team of MIT researchers has beenworking on just that, developing two new solutions that can causesynthetic bacteria to die without the continued presence of certainchemicals. The team describes the solutions as "standalonecircuits" in reference to their ability to be attached to avariety of different organisms without the need to make significantadjustments to the host's genome.

The first solution, known as the"deadman" kill switch is inspired by the breaks you would find on old trains, which required the conductor to keep constant contactwith the pedal or handle for the vehicle to keep moving.

It makes use of a switchthat's able to flip between two states, turning on one of two genes.When a certain molecule is present, the switch stays in a safe state,but once the chemical is removed, it switches, activating a secondgene that releases toxins to quickly kill the host bacteria.

The second solution, known as the"passcode" switch, works a little differently. Rather thanneeding a single chemical to be present, it requires a combination ofchemicals to survive. It contains a selection of separate componentsfor sensing small molecules. If not all of the required chemicals arepresent, then the switch kills the bug immediately.

According to the researchers, thepasscode method is more versatile, as the chemical sensing componentscan be mixed and matched, allowing scientists to create bespoke killswitches. In theory, it could even be used to protecting intellectualproperty.

"Imagine that you own a certain bug,and you don't want your competitors to use it," says lead studyauthor Clement Chan. "Then you could incorporate this device sothat only people who know the passcode can use your bug."

The findings of the research werepublished in the journal Nature Chemical Biology.

Source: MIT

5 comments
Smitty Jl
Hopefully this works better than it did in Jurasic Park.
Just Cause
Jurassic Park Henry Wu: You're implying that a group composed entirely of female animals will... breed? Dr. Ian Malcolm: No. I'm, I'm simply saying that life, uh... finds a way.
I promise this will go wrong, but I hope I'm wrong.
MadMaxx
Nature is resilient. Don't design anything you don't want to escape into a wild state because inevitably it will.
christopher
Cute idea, but, that's not how life works; when you add any "useless" trait to DNA, it will evolve-away in just a few generations. Changing DNA is actually quite easy... getting the changes to *stick*, that's the really hard part we have not worked out yet.
Ralf Biernacki
Detrimental traits evolve away. What will actually happen is this: One day, a scientist somewhere will "turn off" his vat of engineered bacteria by withholding the passcode chemical. The bacteria will die, except for the fittest---the ones that have a mutation in the kill switch DNA. These "feral" bacteria will survive and breed. This is a scenario that nature has carried out in vivo millions of times; it's what evolution is.
The solution? There is no failsafe solution, but there are probabilistic ones. One is to introduce several redundant kill switches, all bases on the same environmental cue, but operating differently and placed at distinct sites in the genome. The odds of a bacterium mutating all of these at once, and remaining viable, are very slim.
Another solution is to bundle the kill switch with an actual metabolic advantage, so that the "tame" bacteria with a functioning kill switch can easily outcompete the mutated feral ones. Then all you would need to do to eliminate the survivor mutants is to put the dependency chemical back in the batch, and reintroduce the tame bacteria to outcompete and extinct the feral ones.