Insights into the microbial strain mediated impact on pest insect development

Molecular analyses of host-associated microorganisms have demonstrated the essential role that the microbiome plays in host development. Approaches targeting the sequencing of ribosomal genes have successfully identified key species of the host-associated microbiome. However, it remains unclear to what extent the strain-specific characteristics influence the outcome of the host-microbiome interactions. This is particularly important for insect pests, where microbial species might be used as targets for biocontrol purposes. Understanding strain-level variation represents thus a crucial step in determining the microbial impact on hosts. To investigate the microbial strain-level effects on an invasive insect pest, Drosophila suzukii, we compared the impact of monocultures and cocultures of different bacterial and yeast strains. We investigated whether different strains of Gluconobacter and Pichia differentially influenced the larval development of the pest. Fly trait measurements demonstrated beneficial, although variable, impact of these microbial strains on the fitness of suzukii. Using cocultures of microbial strains, we found that in some combinations, the beneficial effects were intermediate between those of the respective monocultures. In contrast, in other cases, strong inhibitory effects were observed. Hence, our study reports that strain-level effects within species are present in D. suzukii, reinforcing the importance of assessing the impact of associated microbiota on pest insects at the strain level. HighlightsO_LIMicrobial strains make up an essential part of the diversity of an insect hosts C_LIO_LICharacterizing and accounting for strain-specific impact on a pests life-history traits and different combinations of strains constitute an important step in our understanding of the pest management strategies. C_LIO_LIWe investigated whether there was any strain-specific impact of bacteria and yeasts on the larval development of a frugivorous pest. C_LIO_LIWe observed that strains varied in their impact, both as monocultures and cocultures, indicating their importance in modifying the host ecology. C_LIO_LIOur study adds to the growing literature on the importance of strains in pest insects. C_LI