在线英语听力室_免费在线英语听力学习网站

There’s been an unexpected development in our understanding of drug resistance in bacteria. The accepted scenario¹ was a simple case of evolutionary² selection. In a bacterial³ population exposed to a killer⁴ drug, a few lucky individuals might have a genetic⁵ mutation⁶ that kept them alive. They survived to reproduce, while the rest of the population perished. In short order, the entire colony consisted only of the offspring of the drug-resistant⁷ founders⁸.

But a new study finds that just a few resistant mutants can protect large numbers of normal bacteria that would have been thought to be susceptible⁹ to the drug therapy. The research appears in the journal Nature.

The key seems to be that the drug-resistant mutants produce large amounts of compounds called indoles, which help bacteria tough out tough times. And the indoles from the mutants buck¹⁰ up the regular, nonresistant bacteria. The mutants themselves seem to be acting¹¹ altruistically—their own growth is slowed by their indole production.

The finding should lead to new strategies to fight drug resistance. And it could also improve our take on evolutionary dynamics¹², in systems that apparently¹³ experience selection pressure at both the individual and group levels.

Thanks for the minute. For Scientific American's 60-Second Science, I'm Steve Mirsky.