The coffee berry borer, Hypothenemus hampei, is a pesky beetle. It is thought to destroy $500M of coffee crop annually, affecting some 20M small farms worldwide. The borer spends most of its life cycle buried inside of the coffee berry, feeding on the sacred bean held within. How it is able to do this has been a mystery because caffeine, a bitter tasting alkaloid, is a naturally produced pesticide that is toxic to insects.
A team of researchers found that the beetle is actually unable to tolerate caffeine on its own. Instead, it houses a community of symbiotic gut bacteria that metabolize the toxic molecule on the insect’s behalf, providing a source of carbon and energy for the microbes and detoxified food for the beetle. When given a cocktail of antibiotics, the beetle’s friendly bacteria died and, along with them, the ability to detoxify caffeine. As a result, the caffeine laid waste to the insects, cutting eggs and larvae by 95 percent and preventing the survivors from emerging into pupae or adults. When Pseudomonas fulva, the predominant caffeine-eating microbe found in the borer’s gut, was reintroduced to the insects treated with antibiotics, caffeine was once again metabolized, but the beetle’s reproductive abilities were not restored.
The authors suggest that targeting the coffee berry borer’s microbiome may be a productive method of pest control.