Caffeine typically repels insects, and being exposed to a lot of it can be harmful for insects and humans alike. But for the coffee berry borer? No problem. The beetles love coffee, more than even you do. They expose themselves to so much coffee, in fact, that it's the equivalent of a 150-pound person drinking 500 shots of espresso.
Scientists have finally figured out how the coffee berry borer can thrive off what's toxic to most other living things. The key is gut bacteria, according to research published this week in the journal Nature Communications by Berkeley Lab and U.S. Department of Agriculture scientists.
The coffee berry borers in this study came from Guatemala, Puerto Rico, Hawaii, India, Indonesia and Kenya. Researchers removed the digestive tracts of dead beetles and submerged them in a caffeine solution. They found that 14 species of bacteria -- shared by most of the beetles they studied -- not only survive all that caffeine, but seem to use it as their only source of carbon and nitrogen.
A bacterial strand called Pseudomonas fulva, which has a caffeine-converting gene, was the most prevalent in the beetles' guts. To test its importance, researchers fed a group of living insects a minimal diet along with antibiotics that depleted their gut bacteria. Compared with normally fed insects, the beetles on the antibiotics lost the ability to break down the caffeine, as evidenced by poop full of the stuff.
But when researchers added some Pseudomonas fulva back to their guts, the beetle poop had no caffeine.
Knowing how these beetles can withstand the potency of caffeine could lead to new ways to protect our precious, precious coffee crops.
“Instead of using pesticides, perhaps we could target the coffee berry borer's gut microbiota," the study's lead author and Berkeley Lab scientist Javier Ceja-Navarro said in a statement. "We could develop a way to disrupt the bacteria and make caffeine as toxic to this pest as it is to other insects."