Researchers modify harmless bacteria to kill harmful bacteria

Aug 17, 2011 by Bob Yirka report

(PhysOrg.com) -- Researchers in Singapore have modified the DNA of one type of bacterium, Escherichia coli, to first sense the presence of another bacterium, Pseudomonas aeruginosa, and then to explode, releasing a special kind of toxin that will kill it. Chueh Loo Poh and Matthew Wook Chang of Nanyang Technological University in Singapore, describe their research in Molecular Systems Biology.

P.aeruginosa is a common microbe that is responsible for difficult to treat infections in people, particularly those with comprised immune systems. It generally colonizes the or the and is believed to be responsible for up to ten percent of all . The general approach to treating it is massive amounts of which don’t always work and also tend to kill off good bacteria in the process.

To get around this problem Poh and Chang modified the DNA of E. coli in such a way as to allow it to be able to detect LasR, a molecule used by P.aeruginosa bacteria to communicate with one another. When the LasR is detected, the E. coli begins producing a toxin called pyocin until it’s full, at which point it explodes releasing the pyocin which kills P.aeruginosa by eating holes in its exterior, allowing its innards to pour out.

This approach is the first time that bacteria have been used to kill other bacteria and is a step up in the ongoing battle against infectious diseases. It’s one that is of critical importance due to the dearth of new anti-bacterial drugs; only two new ones have come on the market in the last ten years and the old ones are becoming increasingly ineffective as new strains of bacteria have evolved that are resistant to them.

The research team says that in the lab, the modified E. coli were able to kill up to 99% of the P.aeruginosa when they were in standalone mode. Perhaps more importantly, they were also able to kill off nearly 90% of them when they were banded together in large communities called biofilms, which are notoriously difficult to treat with conventional methods.

The one major obstacle to using such engineered E. coli as a stealth agent, at least at this stage, is its inability to actually hunt for its victim, rather than sit by passively waiting for the right bacterium to pass by before exploding itself. The hope is that other bacteria with sensing abilities could be used instead of E. coli; ones that could actually track down the specific target, perhaps allowing for a kill rate of 100%.

The next step in the testing of the new treatment will be introducing the modified E. coli into mice to see if it will work as well in a live animal, and also of course, to see what side effects might occur.

Explore further: Scientists tap trees' evolutionary databanks to discover environment adaptation strategies

More information: Engineering microbes to sense and eradicate Pseudomonas aeruginosa, a human pathogen, Molecular Systems Biology 7 Article number: 521  doi:10.1038/msb.2011.55

Abstract
Synthetic biology aims to systematically design and construct novel biological systems that address energy, environment, and health issues. Herein, we describe the development of a synthetic genetic system, which comprises quorum sensing, killing, and lysing devices, that enables Escherichia coli to sense and kill a pathogenic Pseudomonas aeruginosa strain through the production and release of pyocin. The sensing, killing, and lysing devices were characterized to elucidate their detection, antimicrobial and pyocin release functionalities, which subsequently aided in the construction of the final system and the verification of its designed behavior. We demonstrated that our engineered E. coli sensed and killed planktonic P. aeruginosa, evidenced by 99% reduction in the viable cells. Moreover, we showed that our engineered E. coli inhibited the formation of P. aeruginosa biofilm by close to 90%, leading to much sparser and thinner biofilm matrices. These results suggest that E. coli carrying our synthetic genetic system may provide a novel synthetic biology-driven antimicrobial strategy that could potentially be applied to fighting P. aeruginosa and other infectious pathogens.

Related Stories

No hiding place for infecting bacteria

Mar 16, 2009

Scientists in Colorado have discovered a new approach to prevent bacterial infections from taking hold. Writing in the Journal of Medical Microbiology, Dr Quinn Parks and colleagues describe how they used enzymes against produc ...

Bacteria 'launch a shield' to resist attack

Nov 02, 2009

Bacteria that cause chronic lung infections can communicate with each other to form a deadly shield against the body's natural defenses. Studying these interactions could lead to new ways of treating bacteria that are resistant ...

Disinfectants may promote growth of superbugs

Dec 27, 2009

Using disinfectants could cause bacteria to become resistant to antibiotics as well as the disinfectant itself, according to research published in the January issue of Microbiology. The findings could have important implic ...

Bacteria toxic to wound-treating maggots

Feb 04, 2010

Bacteria that infect chronic wounds can be deadly to maggot 'biosurgeons' used to treat the lesions, show researchers writing in the journal Microbiology. The findings could lead to more effective treatment of wounds and th ...

Viruses can turn harmless E. coli dangerous

Apr 16, 2009

For her doctorate, Camilla Sekse studied how viral DNA can be transmitted from pathogenic to non-pathogenic E. coli. Viruses that infect bacteria in this way are called bacteriophages. Her findings reveal ...

Recommended for you

How a white rot tackles freshly-cut food

Dec 23, 2014

Researchers sequenced and analyzed the white rot fungus Phlebiopsis gigantea, which can break down fresh-cut conifer sapwood. They also sequenced and analyzed the set of P. gigantea's secreted proteins (secretome) ...

Bacteria could be rich source for making terpenes

Dec 23, 2014

If you've ever enjoyed the scent of a pine forest or sniffed a freshly cut basil leaf, then you're familiar with terpenes. The compounds are responsible for the essential oils of plants and the resins of ...

The origin of the language of life

Dec 19, 2014

The genetic code is the universal language of life. It describes how information is encoded in the genetic material and is the same for all organisms from simple bacteria to animals to humans. However, the ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

Voleure
4 / 5 (1) Aug 17, 2011
and what happens when stuff like this gets out in the wild...
Scottingham
not rated yet Aug 17, 2011
Voleure, it most likely dies a quick death due to being so incapable of handling the intense environments. Also, it likely has kill genes out the wazoo to ensure a quick death in the event of environmental exposure.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.