Lean and mean

时间:2019-03-07 05:06:02166网络整理admin

A FOOD-POISONING bacterium has a clever strategy to cope when nutrients are scarce. Ruth Massey and her colleagues at Trinity College, Dublin, found that Salmonella typhimurium can evolve into a new strain that digests lactose seventy times more efficiently. The new strain only evolves in solutions that create an osmotic pressure, such as those of salts or sugars. “Without salt, the mutants can’t form, but once they have, it’s of no more use to them,” says Massey, who is now at the University of Oxford. In osmotic solutions, the bacteria’s DNA coils up, allowing the lactose-digesting gene to be expressed to a far greater degree (Current Biology vol 9, p 1477). “What we’ve found is an environmental factor that causes an adaptive mutation,