Ten years ago, Gautam Dantas stumbled across a strange phenomenon in the lab: bacteria that were able to feed on antibiotics.
“The story really starts very serendipitously,” said Dantas, who is now a professor of pathology and immunology at Washington University. “Like whoa, there are bugs in the soil that are munching on antibiotics.”
After investigating these antibiotic-eating microbes for the past decade, Dantas and his colleagues have finally unlocked the mystery of how certain bacteria turn a lethal substance into food. Using a series of enzymes, the bacteria detoxify and break apart the antibiotics into edible parts.
The team started by growing four bacterial strains on different potential food sources, including sugar and penicillin.
To figure out how the bacteria were able to eat antibiotics, they had to take a close look at which genes were being expressed. They could then pinpoint specific enzymes the bacteria use to break down and consume antibiotics.
First, the bacteria use an enzyme called beta-lactamase to break a chemical bond in penicillin and detoxify it. Then, using a second set of enzymes, they chop the antibiotic in half and eat part of it.
The implications of the research go beyond simple scientific curiosity, Dantas said.
Understanding how bacteria detoxify and eat antibiotics, for instance, might help us develop ways to address antibiotic contamination in the environment.
“If you’re able to get these bugs well-harnessed and really well-controlled, maybe you could use them to clean up contamination that comes from antibiotics in the clinic or use of antibiotics in agriculture,” he said.
Although human use of penicillin has fallen out of favor, it is still widely used to treat animals in agriculture, including dairy cows. In the United States, farmers often add antibiotics to animal feed, which contaminates surrounding soil and water and can lead to an increase in drug-resistant bacteria.
The microbes from this study are not ready to be put into the environment to clean up antibiotic contamination. But the team has already begun testing whether it’s possible to engineer other types of antibiotic-eating microbes in the lab.
After identifying the genes important for eating antibiotics, researchers transferred them to a specific strain of E. coli, which was able to grow on penicillin.
The research remains ongoing, as the team works to trace the evolution of drug-resistant bacteria and understand how antibiotics affect the human microbiome.
For his part, Dantas said uncovering these microbes a decade ago changed the course of his career.
“This is the longest project I’ve ever worked on,” he said. “It’s taken 10 years to crack it open, but it’s good to be done.”
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