Your gut is a battleground where rival tribes of bacteria armed with poison darts fight for territory – and these battles are often won by armies of traitors made to switch sides by selfish DNA transferred to them by their enemies.

“Side switching may be more common than we have appreciated,” says Brian Hammer, associate professor in the School of Biological Sciences. The bacterium that causes cholera also constantly produces and fires dart guns. While it has been assumed that this behaviour is costly, last year Hammer’s team showed that strains of Vibrio cholerae that don’t produce T6SSs hardly grow any faster than those that do, suggesting that the cost of going around with guns blazing is surprisingly small.