An insect pupal cell with antimicrobial properties that suppress an entomopathogenic fungus

Soil-dwelling insects have developed various mechanisms to defend against pathogen infection. The pecan weevil, Curculio caryae, spends two to three years in the soil inside an earthen cell. We hypothesized that the cell may possess antimicrobial properties. In a laboratory study, we tested the hypothesis using the fungus Beauveria bassiana as a model. B. bassiana is a common endemic pathogen of C. caryae. We compared the number of colony-forming-units on selective media when B. bassiana was exposed to autoclaved soil, non-autoclaved soil, or soil from a C. caryae pupal cell. Soil from C. caryae cells was suppressive to B. bassiana. To our knowledge this is the first report of antimicrobial properties associated with an insect soil cell. The findings expand our knowledge of host-pathogen relationships. Additional research is needed to determine the basis for the suppressive effects observed.