Assessment of mutualism between Bombus terrestris and its microbiota by use of microcolonies

Social 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.