Abstract
The role of a balanced gut microbiota to maintain health and prevent diseases is largely established in humans and livestock. Conversely, in honeybees, studies on gut microbiota perturbations by external factors have started only recently. Natural methods alternative to chemical products to preserve honeybee health have been proposed, but their effect on the gut microbiota has not been examined in detail. This study aims to investigate the effect of the administration of a bacterial mixture of bifidobacteria and Lactobacillaceae and a commercial product HiveAliveTM on honeybee gut microbiota. The study was developed in 18 hives of about 2500 bees, with six replicates for each experimental condition for a total of three experimental groups. The absolute abundance of main microbial taxa was studied using qPCR and NGS. The results showed that the majority of the administered strains were detected in the gut. On the whole, great perturbations upon the administration of the bacterial mixture and the plant-based commercial product were not observed in the gut microbiota. Significant variations with respect to the untreated control were only observed for Snodgrassella sp. for the bacterial mixture, Bartonella sp. in HiveAliveTM and Bombilactobacillus sp. for both. Therefore, the studied approaches are respectful of the honeybee microbiota composition, conceivably without compromising the bee nutritional, social and ecological functions.
Highlights
We investigated the effect on the honeybee gut microbial community of two feed additives: a bacterial mixture (BM) of Lactobacillaceae and bifidobacteria already designed and preliminary tested in field as stimulant to increase productivity of honeybees [23], and a commercial product based on thymol and seaweeds extracts (HiveAliveTM )
A total of 4 feedings were applied to compensate the lack of natural nectar. 18 honey bee colonies were divided into three experimental groups: (1) [HA], in which HiveAliveTM, a commercial product containing thymol, lemongrass and seaweeds, was administered mixed with sugar syrup (1:1 w/v); (2) [BM], in which a bacterial mixture was provided resuspended with sugar syrup (1:1 w/v), and (3) [CTR], the control, with no active ingredient or bacteria applied but with sugar syrup (1:1 w/v)
The health status of the treated honeybee nucs was generally good over the whole trial and no visible sign of disease was recorded in all experimental replicates
Summary
Honeybees (Apis mellifera), in particular, are known to provide valuable ecosystem services, fruit and crop pollination and are reared for honey and other hive products. Colony decline is accelerated by several abiotic stressors, such as atmospheric or soil pollutants, plant protection products (e.g., pesticides) and climate change altering nectar availability or bee biological life-cycle [12,13]. For these reasons, in the last century, many beekeepers have started to rely on antibiotics against some pathogens. Honeybee diseases have not ceased their virulence and the observed high colony mortality rate has not been reduced in some regions, like Europe
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