Dietary modulation of gut microbiota and functional enzymes in savannah honey bees (Apis mellifera scutellata Lepeletier)

Honey bees gather pollen from flowering plants, using it as a vital protein source and, in turn, acquire pollen-associated microbes that interact with their existing gut microbiota. Despite their ecological importance, limited information exists regarding the gut microbiota of African savannah honey bees (Apis mellifera scutellata Lepeletier) and how diet and its associated microbial community influence this crucial internal ecosystem. This study aimed to investigate the differences in gut microbiota between wild honey bees collected during the flowering season and microbially depleted honey bees reared under semi-sterile conditions and fed various protein diets. To achieve this, freshly hatched worker bees were maintained in hoarding cages and assigned one of four protein diets: fresh sunflower pollen, casein, sterilised casein, or sterilised pollen. High-throughput DNA metabarcoding was then employed to compare the microbial composition of the honey bee gut across these groups. Our findings revealed that the gut of microbially depleted honey bees exhibited higher species diversity and richness. Conversely, the non-core gut microbial community predominated in wild bees and those fed the different protein diets. Specifically, Commensalibacter, Bartonella, and Bifidobacterium were the most dominant bacterial genera across all treatments. Interestingly, Gilliamella, a common core gut bacterium, was undetected, while Apibacter was exclusively found in wild honey bees. Furthermore, pollen-associated microbes such as Devosia and Pedobacter were identified solely in the gut of honey bees fed a pollen diet. Functional predictions of the gut microbial community also indicated the presence of key enzymes such as β-glucosidase, β-galactosidase, pyruvate dehydrogenase and phosphoglycerate mutase, which are crucial for enhancing nutrient absorption, digestion, and carbohydrate metabolism. These results underscore the intricate relationship between honey bees, microbes, and plants, offering valuable insights into how diet and its associated microbial communities could shape the gut microbiota of African honey bees. KEY POINTS: • The non-core gut microbiota dominates the African savannah honey bee • The type of diet influenced the microbial diversity and community abundance in the honey bee gut • Key enzymes involved in digestion, nutrition absorption, and carbohydrate metabolism were enhanced in the gut • Pollen-associated microbes found in the diet present potential avenues for probiotic development to improve honey bee health.