The team analyzed 10,000 individual strains of the bacteria and tested whether they could kill other microbes by pitting them against one another in petri dishes. One species, which the scientists dubbed Eleftheria terrae (“free from the earth”), was an especially successful gladiator. The researchers pinpointed E. terrae’s primary weapon, a molecule they named teixobactin, and discovered that it could wipe out the microbes responsible for anthrax and tuberculosis. Teixobactin also saved mice from infections of MRSA (methicillin-resistant Staphylococcus aureus), one of the most infamous superbugs—bacteria that are immune to several different drugs. What’s more, when the researchers coaxed the microbes to evolve resistance to teixobactin, it didn’t work.

In that bag of dirt, Lewis’s team had found an entirely new kind of antibiotic, one of only a few to emerge in the past 50 years—and a potent one at that. The findings, published this January, garnered widespread enthusiasm: “New Antibiotic May Conquer Superbugs,” declared NBCNews.com. “A New Antibiotic That Resists Resistance,” a blog post on National Geographic’s website proclaimed.

Even more exciting is the innovation used to discover teixobactin: the unassuming plastic blocks. Each one is called an iChip, short for isolation chip, so-named because of how it captures microbes from soil. Until now, scientists hunting for antibiotics haven’t been able to study 99 percent of the world’s microbial species because, when ripped from the outdoors and encouraged to grow under desolate laboratory conditions, the vast majority of bacteria die. The iChip overcomes this problem by keeping things dirty: Burying soil microbes in their natural habitat during the culturing process preserves the organic compounds they need to thrive, enticing previously stubborn microorganisms to multiply under human supervision.