In 2007, Valerie McKenzie volunteered for a large study of human body bacteria. It was the dawn of the golden age of the microbe. Researchers were just beginning to understand how bacteria and other microbes in human intestines influence everything from obesity to allergies and infections. McKenzie, a University of Colorado-Boulder biologist, was mildly curious about her "microbiome." But she was more interested in the bacteria living on the skin of frogs and toads.
Amphibian populations worldwide are plummeting, and entire species are going extinct. The West's struggling species include boreal toads and mountain yellow-legged frogs. Invasive species and habitat degradation play a major role, but amphibians are dying even in places with good habitat. Batrachochytrium dendrobatidis, an aggressive fungus commonly known as chytrid, is often to blame.
McKenzie, who was studying the role of farmland conversion and suburbanization in the decline of leopard frogs in Colorado, suspected chytrid was also a factor. When she read a paper about a strain of bacteria found on red-backed salamanders that inhibited chytrid's growth, she began to wonder: What microbes lived on the skin of her frogs and toads? And could any of them fight chytrid?
She captured boreal toads and leopard frogs and swabbed their legs, feet and bellies at research sites near Boulder and Meeker, Colo. She took the samples to Rob Knight, a fellow CU-Boulder biologist who studies the human microbiome. In exchange for DNA analyses of the bacteria on her amphibians, McKenzie volunteered for Knight's study, handing over fecal samples and forehead, armpit and hand swabs. "I was like, 'Whatever you want, can you just run some of my frog samples?' " she laughs. "That's how I got my first data set."
McKenzie and others now hope to harness the breakthroughs of the human-microbe revolution to slow two of wildlife's most prolific – and seemingly unstoppable – modern killers: chytrid, "the worst infectious disease ever recorded among vertebrates," according to the International Union for Conservation of Nature, and white-nose syndrome, a fungal disease that has killed more than 5.7 million bats in North America since 2006.