Dominance of Fructose-Associated Fructobacillus in the Gut Microbiome of Bumblebees (Bombus terrestris) Inhabiting Natural Forest Meadows

Bumblebees are key pollinators in agricultural landscapes. However, little is known about how gut microbial communities respond to anthropogenic changes. We used commercially produced colonies of buff-tailed bumblebees (<i>Bombus terrestris</i>) placed in three habitats. Whole guts (midgut, hindgut, and rectum) of <i>B. terrestris</i> specimens were dissected from the body and analyzed using 16S phylogenetic community analysis. We observed significantly different bacterial community composition between the agricultural landscapes (apple orchards and oilseed rape (<i>Brassica napus</i>) fields) and forest meadows, whereas differences in gut communities between the orchards and oilseed rape fields were nonsignificant. Bee-specific bacterial genera such as <i>Lactobacillus</i>, <i>Snodgrassella</i>, and <i>Gilliamella</i> dominated gut communities of <i>B. terrestris</i> specimens. In contrast, the guts of <i>B. terrestris</i> from forest meadows were dominated by fructose-associated <i>Fructobacillus</i> spp. Bacterial communities of workers were the most diverse. At the same time, those of males and young queens were less diverse, possibly reflecting greater exposure to the colony's inner environment compared to the environment outside the colony, as well as bumblebee age. Our results suggest that habitat quality, exposure to environmental microbes, nectar quality and accessibility, and land use significantly affect gut bacterial composition in <i>B. terrestris</i>.