Honey bees change the microbiota of pollen

Abstract

Background: Pollen, as all other plant tissues, harbors different microorganisms. As honey bees (Apis mellifera) collect and pack pollen they add regurgitated nectar to moisten and glue the pollen grains, possibly changing the microbial composition. Hypothesis: We hypothesize that while packing pollen into their corbiculae, honey bees change the pollen microbiota. Studied species: Brassica napus L., Apis mellifera L. Study site and dates: Avignon, France, 2018. Methods: In this study, we compared the microbiota of clean Brassica napus (Brassicaceae) pollen with that of bee-worked corbicular pollen by 16S rRNA gene targeted amplicon sequencing. We also compared these bacterial communities with those present in nectar, the bee gut and the bee surface as potential inoculum sources. Results: We found that by working pollen, bees increase the bacterial diversity of pollen, by adding honey bee symbionts such as Bombella, Frischella, Gilliamella and Snodgrassella, bee pathogens as Spiroplasma and nectar dwelling Lactobacillus to the new pollen microbiota. Conclusions: The bee gut is an important source of inoculum of the corbicular pollen microbiota. We discuss the implications of these findings and propose future research avenues.