The coffee berry borer beetle destroys coffee crops — it lays its eggs inside the berries, and the larvae can eat through entire fields. But to digest the carbohydrate compounds that make up 60 percent of the berries, the beetles' ancestors stole a gene from the bacteria living in their guts, says Not Exactly Rocket Science's Ed Yong. In a new study published in PNAS, a team of researchers catalogued the genes in the beetle's gut and found that one of them, HhMAN1, creates a protein called mannanase that breaks down the galactomannan carbohydrate in coffee beans. The problem with that, Yong says, is that insects aren't supposed to have mannanases. "[Lead author Ricardo] Acuña found that the borer's gene was more closely related to similar genes in bacteria than to counterparts in plants, fungi, or animals," Yong adds.
Bacterial gene swapping isn't a new thing, he says, but it's much less common to see an exchange of genes among more complex organisms. And even then, it's rare for the swapped genes to have a specific purpose. This study, Yong says, "adds to this exclusive list" of genes that jumped from bacteria to a complex organism with "a clear purpose in its new body."