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Scientists Have Made a Big Step in Figuring Out the Evolution of Superbugs

Antibiotic Resistance

A new study by researchers from Oxford University shows that genetic responses to the stress caused by antibiotics do not help them evolve resistance to medications.

It has long been believed that when bacteria are exposed to antibiotics they modify the definition of a larger group of genes within their genome. One of these responses is known as the SOS response, which produces an increase in the rate of the DNA mutations that occur, and because DNA mutation is an elementary attribute of evolution, it was thought that over time the incentive of this SOS response helps with an increased resistance to antibiotics.

The researchers tested this hypothesis using two strains of the bacterium Pseudomonas aeruginosa where one strain was normal and the other was changed so that the SOS response never activated. The next step was to expose both of these strains to non-lethal doses of an antibiotic called ciprofloxacin.

Scientists observed that bacteria that could activate the SOS response had a short-term advantage because this made reproducing more effective and also repaired some of the damaged DNA. They repeated this process over and over again over 200 generations of bacteria to see how they would evolve. Surprisingly, they found no evidence that the bacteria with the activated SOS evolved into being more resistant to ciprofloxacin. The results didn’t just show that both strains performed equally, they showed too that the strain with the activated SOS response saw a decrease in the SOS response.

Antibiotic resistance, which can create superbugs, is one of the biggest health problems, so one of the most important things would be to find out how antibiotic resistance evolves. Some scientists have suggested that it would be good to develop drugs that block the SOS response, but this study concludes that this could be the wrong path to follow to tackle antibiotic resistance.

This study has been published in the journal Proceedings of the Royal Society B in a research paper called: “The SOS response increases bacterial fitness, but not evolvability, under a sublethal dose of antibiotic”.

About the author

Dean Smith