Abstract
Adult honeybees harbor a specialized gut microbiota of relatively low complexity. While seasonal differences in community composition have been reported, previous studies have focused on compositional changes rather than differences in absolute bacterial loads. Moreover, little is known about the gut microbiota of winter bees, which live much longer than bees during the foraging season, and which are critical for colony survival. We quantified seven core members of the bee gut microbiota in a single colony over 2 years and characterized the community composition in 14 colonies during summer and winter. Our data show that total bacterial loads substantially differ between foragers, nurses, and winter bees. Long-lived winter bees had the highest bacterial loads and the lowest community α-diversity, with a characteristic shift toward high levels of Bartonella and Commensalibacter, and a reduction of opportunistic colonizers. Using gnotobiotic bee experiments, we show that diet is a major contributor to the observed differences in bacterial loads. Overall, our study reveals that the gut microbiota of winter bees is remarkably different from foragers and nurses. Considering the importance of winter bees for colony survival, future work should focus on the role of the gut microbiota in winter bee health and disease.
Highlights
The European honeybee, Apis mellifera, is an important pollinator species for natural ecosystems and agricultural production [1]
This became evident from the abundance of individual phylotypes and from the total bacterial load inferred from the summed abundances of all seven phylotypes (Supplementary Fig. S3, Fig. 1a)
The overall bacterial load was about 10× larger in winter bees than in foragers based on both the summed abundances of all seven phylotypes (Fig. 1c, Permutation T-Test P = 1e–4) as well as the number of total 16S rRNA gene copies, which was determined with universal 16S rRNA gene quantitative PCR (qPCR) primers for a subset of the samples (Fig. 1d, Permutation T-Test, P = 1e–4)
Summary
The European honeybee, Apis mellifera, is an important pollinator species for natural ecosystems and agricultural production [1]. Its health status is threatened by numerous factors including habitat loss, pesticide exposure, and high parasite and pathogen loads [2,3,4]. Accumulating evidence suggests that the gut microbiota of adult honeybees plays a critical role for bee health [5]. The bee microbiota converts dietary compounds [6, 7] and produces short-chain fatty acids [8] in the gut, enhances sucrose responsiveness of the. Joint first authors: Lucie Kešnerová, Olivier Emery. Joint last authors: Berra Erkosar, Philipp Engel
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