The bacteria coat the walls of the Lechuguilla cave system on rock faces some 1,600 feet (487 meters) below Earth’s surface. Until recently, the microscopic life-forms had encountered neither humans nor modern antibiotics.
That’s because a thick dome of rock isolated the cave between four and seven million years ago. Any water that trickles through takes roughly ten thousand years to reach the cave’s depths—which means the subterranean life has existed entirely in the absence of modern medicine.
While not infectious to humans, the cave bacteria can resist multiple classes of antibiotics, including new synthetic drugs. The discovery serves as an intriguing lead in the quest to understand how drug-resistant diseases emerge.
“Clinical microbiologists have been perplexed for the longest time. When you bring a new antibiotic into the hospital, resistance inevitably appears shortly thereafter, within months to years,” said study leader Gerry Wright, a chemical biologist at McMaster University in Ontario.
“It’s still a big question: Where is this coming from?” Wright said. “Almost no one thought to look at other bacteria, the ones that don’t necessarily cause disease.”
The U.S. National Park Service strictly limits entry to the cave, but since 2008 the agency has allowed geomicrobiologist Hazel Barton of Northern Kentucky University and her team into the cavern to sample its microbial life.
“Hazel sampled sites clearly not touched by humans before. Because it’s so pristine, you can see where people—all of the people—have walked,” Wright said. “It’s a serious stretch of the imagination to think any of the sites sampled have seen significant impact by anything from the surface.”
Barton scraped off and bagged samples of biofilms—thick mats of bacteria—growing on the cave walls and delivered them to Wright’s laboratory, where his team spent three years probing the samples for any signs of antibiotic resistance.
Disease-causing bacteria have grown increasingly resistant to many of the dozens of classes of antibiotics used to fight them. Such strains, often calledsuperbugs, can immobilize, chew up, or block natural and synthetic antibiotic compounds.
Superbugs almost always appear in hospitals and on animal farms, where antibiotic use is prevalent. In these environments, intense evolutionary pressure pushes microbes to quickly develop resistance to multiple drugs.
But how this happens is a frustrating problem, Wright said, considering that studies suggest the preponderance of antibiotic-fighting genes should have taken thousands or millions of years to emerge.
National Geographic has the full article