Like nicotine and other compounds produced by plants, caffeine can be lethal to insects. However, the coffee berry borer (Hypothenemus hampei) is able to feed on coffee beans and survive.
Now researchers have discovered how. The bacteria in the borer’s gut allows it to break down the caffeine, according to a study published in Nature Communications.
“This opens a door to potentially new pest management strategies, and it adds to a growing body of research showing how a wide range of organisms, from insects to humans, use their internal microbial profiles to adapt and survive,” said Fernando Vega, a USDA-ARS entomologist and one of the authors.
He and his colleagues analyzed coffee berry borers from seven coffee-producing regions: Guatemala, Hawaii, India, Indonesia, Kenya, Mexico, and Puerto Rico, as well as from Vega’s laboratory-reared colony in Beltsville. They removed the digestive tracts from the tiny beetles — a painstaking process — and then placed the mashed-up digestive tracts in a caffeine-rich medium to see which bacteria would grow in it. That way, only the bacteria that degraded caffeine would survive. They found 14 bacterial species that degraded and detoxified caffeine. Most of those bacteria were in borers from all seven coffee-producing regions, and one bacterial species, Pseudomonas fulva, was the most prevalent.
To confirm that the bacteria degrade caffeine, they gave the beetles an antibiotic to wipe out the bacteria and fed those beetles a standardized diet of coffee beans. They found that the caffeine passed through the beetles’ digestive tracts intact, without degrading. Though the beetles survived, their capability to produce eggs and larvae declined by 95 percent. The scientists next added the caffeine-digesting Pseudomonas fulva bacteria back into the beetles’ diet and found that their feces were devoid of caffeine, which showed that the bacteria are key to the detoxification process.
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