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Bacteria thrive by freeloading

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11:50am, October 15, 2007

They say that cheaters never win, but some bacteria appear to do quite well by adopting this strategy.

The guilty party is a mutant form of the bacterium Pseudomonas aeruginosa, which can infect people with weakened immune systems and is often the cause of death among people with cystic fibrosis. Because this species is effective only in large numbers, the bacteria wait until they sense chemical messages from many nearby individuals before they begin producing the toxins that cause their virulence—a process called quorum sensing.

Scientists had been puzzled that some bacteria in samples taken from infected people had mutations that caused them to ignore quorum sensing. Losing the ability to detect when the bacterial population reaches critical mass seemed to be a detrimental trait that natural selection would weed out.

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