It's one of the underwater world's classic partnerships: clownfish and [Finding Nemo clip: "Anemonenene. Anemonem. Monemone."] Nemo hides out in the anemone, which helps keep predatory fish at bay. 

"But at the same time there are other fish species that will kind of nibble on the sea anemones, and the clownfish will actually go out and scare them away." Jeff Gore, a biophysicist at MIT. "So in this case there's a cross-protection mutualism between these two species in which they help to avoid predation."

Such cross-protection is usually seen between two animals. But Gore studies the same sort of mutualism in microbes. He and his team demonstrated the first experimental example of that cross-protective relationship in drug-resistant microbes, using two strains of antibiotic-resistant E. coli bacteria: one resistant to ampicillin, the other to chloramphenicol. 

The researchers grew the bacteria together in a test tube, in the presence of both antibiotics. And rather than succumbing to the drugs, each bacterial strain deactivated one of the two antibiotics—thus protecting the other strain. That activity led to a stable coexistence over time. Which Gore says could in theory give the bugs an opportunity to swap resistance genes, through what’s called horizontal gene transfer—one bacterium donates genetic material to another. Any such transfer could make either or both strains individually resistant to both types of antibiotics. The findings are in the Proceedings of the National Academy of Sciences. [Eugene Anatoly Yurtsev, Oscillatory dynamics in a bacterial cross-protection mutualism]

The same story might play out in our guts, too—but it's too early to translate it into medical guidance. "It's always important to remember that just because we see a particular dynamic in the laboratory doesn't mean we should immediately go and change our clinical dosing practices. But then those sorts of results are then used as a guide for the kinds of phenomena that clinicians may want to watch out for in their circumstances." ‘Cause the more we know about this bacterial buddy system, the better we may be at breaking it up if they team up against us.

—Christopher Intagliata

[The above text is a transcript of this podcast.]