The coffee berry borer thrives on toxic levels of caffeine. These two-millimeter beetles consume the equivalent of a 68-kilogram (150-pound) person drinking 500 shots of espresso. But with its bitter taste and paralyzing effects, caffeine is supposed to be a natural insect repellent. As it turns out, the beetles rely on gut microbes to break down all of that caffeine, according to new work published in Nature Communications.

These borers are some of the world’s most economically devastating insect pests: Infestations can slash coffee crop yields by 80%. Their entire life cycle is completed within the coffee bean, which is their sole source of food and shelter. After drilling into the berry that houses the bean, a gravid female can lay up to 120 eggs in that one berry. The larvae feed on the bean and within a month, the daughters emerge to infest more.

To better understand their caffeine-rich diet and metabolism, a team led by Lawrence Berkeley National Laboratory and U.S. Department of Agriculture (USDA) researchers studied the gut of coffee berry borers, Hypothenemus hampei, from seven coffee-producing countries: Guatemala, Hawaii, India, Indonesia, Kenya, Mexico, and Puerto Rico. They also studied a colony raised in a USDA lab.

Using micro-tweezers, the researchers removed the digestive tracts of hundreds of dead beetles. “Before this research, I worked with atomic force microscopy, where you have to keep your hands steady, so I got good at it,” Berkeley Lab’s Javier Ceja-Navarro says in a statement. “But I had to cut down on coffee!”

They found that all of the specimens harbor a common, core population of 14 species of bacteria that subsist on caffeine for carbon and nitrogen. The most prevalent of them was Pseudomonas fulva, which has a gene called ndmA, which is known to break down caffeine.

Using antibiotics, the researchers wiped out the gut microbiota of the coffee fiends: Their feces showed that caffeine passed through their digestive system without being degraded. The insects' ability to detoxify caffeine was eliminated, resulting in substantial declines. However, when the team fed Pseudomonas to the antibiotic-treated beetles, they were all hopped up on caffeine again. 

“Instead of using pesticides, perhaps we could target the coffee berry borer’s gut microbiota,” Ceja-Navarro adds. “We could develop a way to disrupt the bacteria and make caffeine as toxic to this pest as it is to other insects.”

^{A coffee berry borer (lower left) sits atop a coffee bean, which is its sole source of food and shelter. The beetle thrives in the toxic, caffeine-rich bean thanks to the microbes in its gut, shown in the green microscopy image. A schematic of a caffeine molecule is also shown.}

Images: Shutterstock (top), Department of Agriculture (middle), Berkeley Lab (bottom).

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