But Sebastian Winter, from the University of Texas Southwestern Medical Center, has an alternative. His team showed that the blooming enteros rely on enzymes that, in turn, depend on the metal molybdenum. A related metal—tungsten—can take the place of molybdenum, and stop those enzymes from working properly.

By feeding mice small amounts of tungsten salts, Winter’s team managed to specifically prevent the growth of enteros, while leaving other microbes unaffected. Best of all, the tungsten treatment spared the enteros under normal conditions, suppressing them only in the context of an inflamed gut. It’s a far more precise and subtle way of changing the microbiome than, say, blasting it with antibiotics. It involves gentle nudges rather than killing blows.

To be clear, no one knows if this would work in people. “We can cure inflammatory bowel disease in mice, and that’s the best we can say at this point,” Winter says. “We’re far away from having a treatment. And of course, tungsten is toxic, so this is not an endorsement that people with IBD should drink tungsten-contaminated water. But we can now screen for molecules that have the same activity without the toxicity.”

“It shows that the microbiome can indeed be edited if we understand how certain organisms thrive in a given environment,” says Manuela Raffatellu, from the University of California at San Diego. And that understanding, she adds, takes years of work.

Many teams, for example, have shown how enteros both bloom in inflamed guts, and trigger inflammation themselves. And Winter’s team has uncovered several of the tricks behind their ascension. These microbes are typically found in low numbers because they need oxygen to grow, and the gut is an oxygen-free world. But during inflammation, oxygen leaks through, and its presence allows enteros to devour a chemical called formate, produced by other gut microbes. “They can eat the scraps off the table,” Winter says. Inflammation also causes host cells to release nitrates, and the enteros can “breathe” using these instead of oxygen.

These discoveries all pointed to a single Achilles’ heel. It turned out that the enzymes that allow enteros to process both formate and nitrates—that allow them to eat and breathe—use a single atom of molybdenum. Tungsten is similar to molybdenum, sitting right beneath it in the periodic table. It’s chemically similar enough that it can substitute for the other metal in the bacterial enzymes, but different enough that once this happens, those enzymes are dead. They don’t work, and the enteros can’t grow.

That’s what Winter and his colleagues found. Team members Wenhan Zhu and Maria Winter fed tungsten salts to mice that had been previously dosed with DSS—a chemical that inflames the gut. Enteros would normally bloom vigorously in such conditions, but the tungsten reduced the numbers by almost a million times. It didn’t, however, affect the rest of the microbiome.