Coffee Beetle Withstands Extremely Toxic Concentrations of Caffeine

Coffee Berry Borer

The coffee berry borer is the most destructive coffee pest in the world.  This coffee beetle, found in most regions where coffee is cultivated, can reduce a crop yield by 80 percent.

This insect is the only coffee pest that uses the coffee beans as its sole source of food.  It bores into the bean and spends most of its life tucked inside, where it’s exposed to what we might think would be an extremely toxic amount of caffeine for its mass:  the equivalent of a 150-pound person drinking 500 shots of espresso.

Caffeine evolved as an insecticide and anti-microbial to protect plants.  But the coffee berry borer relies on the bacteria in its gut to degrade and detoxify caffeine.  Researchers also found the most prevalent of these bacteria boasts a gene that helps break down caffeine.

The war against the coffee berry borer beetle continues.  “Instead of using pesticides, perhaps we could target the coffee berry borer’s gut microbiota.  We could develop a way to disrupt the bacteria and make caffeine as toxic to this pest as it is to other insects,” says Javier Ceja-Navarro, a scientist in Berkeley Lab’s Earth Sciences Division and lead author of the paper.

The scientists analyzed coffee berry borers from seven coffee-producing regions:  Mexico, Guatemala, Puerto Rico, Hawaii, India, Indonesia and Kenya.  They also studied a colony reared at the USDA’s lab in Beltsville, Maryland.

The scientists immersed the gut bacteria in a special medium containing caffeine as the main nutrient, so only the bacteria that degrade caffeine survived. Fourteen bacterial species were isolated, most of which were found in beetles from all seven coffee-producing regions and the laboratory colony.  These bacteria appear to subsist on caffeine as their sole source of carbon and nitrogen.  One of the bacteria, Pseudomonas fulva, was the most prevalent, according to their DNA-based geographic survey.

The research was funded by the U.S. Department of Agriculture, the Laboratory Directed Research and Development program at Berkeley Lab, and Mexico’s National Council for Science and Technology.

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