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Viruses turbo-charge bacterial evolution in cystic fibrosis infections

Posted on 5 July 2016

Scientists at the University of York have found new evidence that tiny viruses called bacteriophages turbo-charge the evolution of bacteria that cause lung infections in Cystic Fibrosis patients.

Scanning electron microscope images of phages

The research team warn that antibiotics can activate bacteriophages, meaning certain medical therapies might make the infections even more difficult to treat.

Cystic Fibrosis (CF) patients suffer from life-long lung infections caused by the environmental bacterium Pseudomonas aeruginosa.

These infections worsen patient health and limit life-expectancy. Over the years of the infection, the bacteria evolve to become better adapted to the lung environment, becoming very difficult to treat.

The scientists found new evidence that viruses infecting the bacteria, called bacteriophages, can speed-up this bacterial evolution.

A team of scientists from the Universities of York, Liverpool and Salford evolved populations of the bacterium P. aeruginosa with or without bacteriophages in a growth medium designed to replicate the sputum in CF lungs. They then tracked evolutionary change in the bacterium using genome sequencing.

The study, published in the Proceedings of the National Academy of Sciences, reports that bacteria with bacteriophages evolved faster to adapt to life in sputum. This happened because the bacteriophage jumped into the bacterium’s DNA, increasing the number of useful mutations that natural selection could use.

Many of the mutations seen in the lab-evolved bacteria, including those caused by the bacteriophage, are also commonly seen in bacteria isolated from CF infections. Because bacteriophages live wherever you find bacteria, including in the lungs of CF patients, this could mean that they play an important role in bacterial evolution in the clinic.

Professor Michael Brockhurst, from the University of York’s Department of Biology, said: “To design better treatments and preserve our antibiotics we urgently need to better understand how bacteria evolve in infections.

“These new results suggest that bacteriophages may play a much bigger role than previously thought, by turbo-charging evolutionary adaptation.”

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