A MiSeq multiplexed 16S rRNA amplicon sequencing of the gut microbiota of wild and indoor-reared Bombus terrestris (bumblebees) confirmed the presence of a core set of bacteria, which consisted of Neisseriaceae (Snodgrassella), Orbaceae (Gilliamella), Lactobacillaceae (Lactobacillus), and Bifidobacteriaceae (Bifidobacterium). In wild B. terrestris we detected several non-core bacteria having a more variable prevalence. Although Enterobacteriaceae are unreported by non next-generation sequencing studies, it can become a dominant gut resident. Furthermore the presence of some non-core lactobacilli were associated with the relative abundance of bifidobacteria. This association was not observed in indoor-reared bumblebees lacking the non-core bacteria, but having a more standardized microbiota compared to their wild counterparts. The impact of the bottleneck microbiota of indoor-reared bumblebees when they are used in the field for pollination purpose is discussed.

Social bees, like honeybees and bumblebees, have a close contact with nest mates of different developmental stages and generations. This could enhance bacterial transfer between nest mates and offers opportunities for direct transfer of symbionts from one generation to the next, resulting in a stable host specific gut microbiota. Gut symbionts of honeybees and bumblebees have been suggested to contribute in digestion and protection against parasites and pathogens. Here we studied the impact of contact with the bumblebee colony on the colonization potential of the bacterial families (i.e., Neisseriaceae, Orbaceae, Lactobacillaceae and Bifidobacteriaceae) occurring in the gut of adult bumblebees (Bombus terrestris). Bacterial profiles of the gut microbiota of B. terrestris were determined based on the hypervariable V4 region of the 16S rRNA using paired-end Illumina sequencing. In our experiments, we created different groups in which we gradually reduced the contact with nest mates and hive material. We made 3 observations: (i) reducing the contact between the colony and the bumblebee during adult life resulted in a significant drop in the relative abundance of Lactobacillus bombicola and Lactobacillus bombi; (ii) Bifidobacteriaceae required contact with nest mates to colonize the gut of B. terrestris and a significant lower bacterial diversity was observed in bumblebees that were completely excluded from colony contact during the adult life; (iii) Snodgrassella and Gilliamella were able to colonize the gut of the adult bumblebee without any direct contact with nest mates in the adult life stage. These results indicate the impact of the colony life on the diversity of the characteristic bumblebee gut bacteria.

International audienceSocial pollinators, like honeybees and bumblebees, have specific microbiota. The specific association between the insect and its gut microbiota could lead to a functional dependence. In this project, we investigated whether an alteration in microbiota could influence the fitness of the generalist pollinator Bombus terrestris. We used bumblebee workers in microcolonies to assess effects on colony development and reproduction. Treatment with 200 ppm streptomycin and tetracycline resulted in a disruption of gut microbiota, and typically there was 100 % worker mortality. In contrast, treatment with streptomycin alone showed an improved reproduction and this concurred with a different gut microbiota pattern. The results are discussed in relation to effects of the gut microbiota on bumblebee fitness and potential beneficial effects by Lactobacillus sp. These data may open new avenues in the mass-rearing of bumblebees used for the biological pollination in agriculture

In this project, we showed the influence of diet on the microbial composition in the gut of indoor-reared bumblebees (Bombus terrestris), using Illumina MiSeq 16S ribosomal RNA (rRNA) sequencing. Three sugar syrups and sterilized pollen from three suppliers were tested. Different effects were observed depending on the developmental stage of the gut microbiota at the start of the dietary treatment. Fructose-rich sugar syrup prevented the colonization of Bifidobacteriaceae in the microbiota of newly emerged bumblebees. This effect was correlated with a lower bacterial community richness and diversity. The pollen diet with the best parameters, regarding the protein content and bumblebee offspring, showed the lowest bacterial richness and diversity. The interaction between diet and the microbiota of bumblebees provides new insights for bumblebee breeders. Diet could be used to modulate the bacterial composition in the gut to improve the health of mass-produced bumblebees used for biological pollination. Bombus terrestris / gut microbiota / pollen / carbohydrate / rearing facilities Electronic supplementary material The online version of this article (

-In this study, we investigated if oral administration of lactic acid bacteria could increase the colony performance of reared bumblebees. We found that a continuous administration of Lactobacillus kunkeei LMG 18925 and Lactobacillus crispatus LMG 9479 could partly compensate the effects of low nutritional pollen, but a permanent colonization in the gut was not detected with Illumina MiSeq 16S rRNA sequencing. Contrary to expectations, a single administration of L. kunkeei LMG 18925 to a high nutritional pollen led to a lower total drone mass. A Bombus -specific strain, Bifidobacterium actinocoloniiforme R-53049, showed potential to colonize the gut permanently after three administrations. Our study represents a first screening for the potential use of probiotic strains in bumblebees. We conclude that both diet and host specificity of bacteria might have an effect on colony performance of indoor-reared bumblebees and play a role in the gut colonization success.Bifidobacterium / Lactobacillus / probiotics / Bombus terrestris / colony development / gut microbiota

The results suggest that the microbiota can modify the susceptibility of E. mundus to pesticides, which in turn supports the importance of the microbial community in natural enemies that it should be considered as a factor in risk assessment tests of pesticides. © 2018 Society of Chemical Industry.

17The cholecystokinin receptor-type 1 (CCK1R) is a G-protein coupled receptor localized in the 18 animal gastrointestinal tract. Receptor activation by the natural peptide ligand CCK leads to a 19 feeling of satiety. In this study, hydrolysates from soy and milk proteins were evaluated for 20 their potential to activate CCK1R, assuming that bioactive peptides with a satiogenic effect 21 can be used as an effective therapeutic strategy for obesity. Different protein hydrolysates 22were screened with a cell-based bioassay, which relies on the generation of a fluorescent 23 signal upon receptor activation. Fluorescence was monitored using a fluorescence plate reader 24 and confocal microscopy. Results from the fluorescence plate reader were biased by 25 background autofluorescence of the protein hydrolysate matrices, which makes the 26 fluorescence plate reader inappropriate for the evaluation of complex formulations. 27Measurements with the confocal microscope resulted in reliable and specific results. The 28 latter approach showed that the gastrointestinal digested 7S fraction of soy protein 29 demonstrates CCK1R activity. 30 31

The interaction between the insect host and its microbiota plays a central role in insect health and is mostly studied in relation to the digestive system. Nonetheless, there are numerous microorganisms occupying multiple habitats in and on insects. We studied microbial communities in the gut and fat body of bumblebees (Bombus terrestris) using the V4 region of the 16S rRNA gene on the Illumina MiSeq platform. In one of the two study locations, the fat body microbial composition was marked by the dominant presence of Arsenophonus sp. and Phyllobacterium sp. Bumblebees infected with Apicystis bombi, a eukaryotic parasite multiplying in the fat body, had a significant higher relative abundance of Arsenophonus sp. compared with the non-infected individuals. In general, the infection of A. bombi correlated with a more interlinked microbial association network, as we observed an increase of significant associations between the relative abundance of bacteria present in the gut and fat body of infected bumblebees. The causality within this potential prokaryotic-eukaryotic relation is important when assessing the health impact on bees.