The bee bread of honey bees is characterized by a core microbiota despite the application of miticide treatments and variation across space and time.

Background: Bee bread is composed of a mixture of pollen and nectar used as the main source of proteins and lipids for the development of bee larvae. Despite its important role in honey bee food preservation, relatively little is known about the composition of bee bread microbiota and the potential impact of beekeeping management of hives on these microbial systems. Methods: Here, we evaluated whether (1) the bee bread of honey bees is characterized by a core microbiota and (2) miticide applications (formic acid and amitraz) affect the diversity and composition of the bee bread microbiota. We collected a total of 36 samples from six sites across two distinct geographic locations and sequenced the bee bread bacterial communities before and after miticide applications. Results: Our results revealed a conserved bee bread core microbiota comprised of 15 taxa belonging to the phyla Proteobacteria (11 taxa), Firmicutes (two taxa), Actinobacteriota (one taxon), and Bacteroidota (one taxon). In addition, we found weak evidence of miticide treatments impacting the diversity of the bee bread microbiota, with a general trend of a decrease in the diversity of non-core taxa following the application of organic miticides. Conclusion: Taken together, our results demonstrate that the bee bread of honey bees is characterized by a core microbiota despite variations associated with geographic location, sampling period, and miticide applications.