Bacteria associated with the mountain pine beetle degrade components of tree defensive chemistry

When mountain pine beetles (Coleoptera: Curculionidae) attempt to colonize healthy hosts, trees respond by accumulating high concentrations of defensive chemicals at the point of attack. These compounds consist largely of monoterpenes and diterpene resin acids that inhibit both beetles and their symbiotic fungi. We evaluated whether bacteria associated with the mountain pine beetle degrade these terpenoids, thus potentially assisting in host colonization. We found that some bacteria grew in terpene-amended media and, with some bacteria, terpenes were degraded. Additionally, we detected genes involved in degradation of both mono- and diterpenes from bacteria associated with beetles and their galleries. These results suggest that beetle-associated bacteria may be important contributors to the ability of bark beetles to survive in, and kill trees.