Kamikaze bacteria to fight lethal infections

Researchers have designed bacteria to kill other bacteria… by exploding themselves.

These suicide bacteria are actually engineered E. coli with a mission: find and kill the infection-causing Pseudomonas aeruginosa – one of the leading causes of hospital-acquired infections.

Resistant to common antibiotics, the human pathogen P. aeruginosa causes lethal infections in the lungs and guts of critically-ill patients or those with otherwise weakened immune systems.

A little fact: when P. aeruginosa sense others impeding in their space and nutrients, they start releasing toxic compounds called pyocins to kill off the competition.

So a team led by Chueh Loo Poh and Matthew Wook Chang from Nanyang Technological University in Singapore exploited that natural system, using the pathogen’s own weapons against itself.

1. They gave the genes for pyocin to a strain of E. coli.
2. These E. coli were also engineered with the ability to detect the presence of P. aeruginosa – by intercepting chemical signals that these pathogens naturally use communicate with each other.
3. When the engineered E. coli sense nearby P. aeruginosa, they produce toxic pyocins, and then they burst open – BURST! – killing themselves and flooding the local environment with toxins.

In a dish with suicide bacteria, 99% of the pathogens were killed. And the P. aeruginosa biofilms – virulent colonies super resistant to antibiotics – were also much thinner and sparser when the engineered E. coli were around.

And! This pyocin treatment wouldn’t affect any of the body’s good bacteria. "Pyocins are the Pseudomonas bacterium's own species-specific antibiotics, so using pyocins instead of broad-spectrum synthetic antibiotics might help slow the spread of antibiotic resistance," Chang says.

The team plans to test this treatment in mice with P. aeruginosa infections. If successful, they envision a probiotic drink that immunocompromised patients could take to prevent infection.

Maybe later, according to Chang, “we can easily develop another type of engineered bacteria to target other infectious pathogens.”

One important caution: "be very wary of putting live E. coli onto a burn or into the respiratory tract, which is where we often see Pseudomonas infections, but where you don't want to add bacteria," says a microbiologist at the Health Protection Agency Centre for Infections in London. The engineered bacteria might be more useful in treating infections in the gut, where bacteria are already abundant.

The bacteria were constructed using tools from the newish field of synthetic biology, which builds complex living devices that aren’t found in nature. In this case, the researchers connected the genetic components for recognizing P. aeruginosa, creating pyocin, and committing explosive suicide, so that the first event would trigger the latter two.

The study was published in Molecular Systems Biology earlier today.

Image: E. coli colonies / CDC Public Health Image Library

This post was originally published on Smartplanet.com