In the Mojave Desert of the western United States, the adorable desert woodrat fills its stomach with deadly poison. This rodent feeds on the creosote bush, a low-lying shrub whose leaves are covered in a toxic resin. The resin is a cocktail of hundred of chemicals and chief among them is nordihydroguaiaretic acid or NDGA—a chemical that wrecks the liver and kidneys of lab mice. But the woodrat doesn’t seem to mind. Every single day, it swallows resin in amounts that would kill a normal mouse.

When Kevin Kohl learned about the woodrat, he wondered if bacteria in the rodent’s gut might help it to tolerate its otherwise lethal diet. After all, bacteria are such biochemical virtuosos that they