The Plight of the Bumble Bee: The Impact of the Bumble Bee Gut Microbiome on Pathogen Infection Rates

Bumble bees are one of the most common and important non-managed pollinators of agricultural crops and are therefore vital to society’s ecological and agricultural health. Recent declines in bumble bee populations, likely due to pathogens and land-use change, are concerning and have led to subsequent research on pathogen vulnerability and resistance in bumble bees. Social bumble bees have a specific and relatively consistent gut microbiome. The bumble bee microbiome is typically dominated by only a few bacterial species, and is important for both general and specific resistance against pathogen infections. This gut microbial community has been specifically associated with increased pathogen resistance against the trypanosomatid pathogen Crithidia bombi, which is known to increase bumble bee mortality under harsh conditions. Currently little is know about how differences within the microbial community impact rates of infection by Crithidia. We examined how differences in the microbiomes of wild and commercial bumble bees may impact Crithidia infection rates. Wild and commercial bumble bees were inoculated with microbiomes from both wild and commercial bees, and then infected with Crithidia. We found that high OTU diversity, evenness of gut population, and presence of Apibacter and Saccharibacter in the gut community were all correlated with lower Crithidia infection rates. These results indicate that even relatively minor differences between microbial communities can have a significant impact on the microbiome’s ability to help protect against pathogen infections.