1st Place: The mechanism behind beneficial effects of bee-associated fungi on bumble bee health

Social bee colonies often contain food stores with associated microbial communities, including filamentous fungi and yeasts. These fungi are common inhabitants of stored pollen and nectar within bumble bee colonies, and we have previously found that inoculating food sources with these bee associates can improve bumble bee survival and increase reproductive output. It is possible that these positive effects are due to use of fungal cells as a food source by bumble bees, modification of provisions by fungi in a way that makes them more nutritionally valuable, or a combination of these two. This research aims to determine the mechanisms underlying positive impacts of fungal supplementation in the agriculturally important bumble bee, Bombus impatiens. To test this, we created microcolonies (queenless colonies) of this species, and exposed each microcolony to one of four treatment groups. These four treatments were created based on the presence of fungal cells, the presence of fungus-modified media, a combination of these two factors, or sterile provisions as a control. Survival and offspring production of each microcolony was measured, and pollen and nectar of each treatment were used for metabolomics analysis to identify compounds that differed between treatments. Results are in progress, but display a trend of higher bumble bee survival in microcolonies given access to living fungal cells.