AP Photo

In 2008, nearly 300,000 infants in China got sick from milk formula tainted with melamine, a plastics additive that was used illegally to bulk up the formula's apparent protein content. Now, a study in rats implicates bacteria living in the gut as unwitting accomplices in this mass poisoning. The work helps clarify how melamine toxicity arises and also drives home the key role that gut bacteria play in human health.