Pesticide degradation by Caballeronia symbionts in the gut of Leptoglossus zonatus

In recent years, a phenomenon known as symbiont-mediated detoxification has led to insights on how host-microbe interactions can provide avenues for insecticide resistance. One of the best-documented examples of this phenomenon occurs in the bug-Caballeronia symbiosis. Many species of true bugs are dependent upon environmentally acquired bacterial symbionts in the genus Caballeronia for normal development and many vital host biological processes. In addition, in one host species (Riptortus pedestris, Alydidae) it has been shown in one species that Caballeronia that can degrade the pesticide fenitrothion can confer pesticide resistance to the host insect.

We set out to determine whether symbiont-mediated pesticide resistance is conferred to other true bugs, specifically the western leaf footed bug (Leptoglossus zonatus, Coreidae). As a generalist pest and vector for Nematospora coryli, a crop rotting yeast, L. zonatus poses a threat to a variety of crops. Given that Caballeronia symbionts are free-living before acquisition by the host and >5% of their genome is dedicated to secondary metabolism, exposure to insecticides in agricultural soils could provide the right conditions for the evolution of pesticide degradation. We surveyed a Caballeronia isolate library spanning across four states for degradation of four representatives of commonly used pesticide families: neonicotinoids, organophosphates, and synthetic pyrethroids. We then selected five geographically districted isolates and attempted to artificially select for insecticide degradation in vitro. Partial degradation of imidacloprid and fenitrothion was documented within two different strains of Caballeronia. However, a month of exposure to both insecticides in vitro did not induce higher degradative abilities.