Dynamics of gut microbiome upon pollination in bumblebee (Bombus terrestris)

Bumblebees are crucial buzz pollinators of poricidal plants and commercial crops. The population of these crucial pollinators is globally declining. The need to focus on factors contributing to bee health such as gut microbiota is imperative. We evaluated the effect of source on gut microbiota composition in adult worker Bombus terrestris from two environments using multiplexed 16S rRNA amplicon sequencing on the Illumina MiSeq platform. Indoor reared adult worker bees were segregated into non-pollination (NP) and pollination (P) groups. The NP group bumblebees were raised and kept in the insectary for the entire experiment. P group bumblebees worked in a tomato-planted greenhouse for 15 days as pollinators. Our results show that members of Proteobacteria and Firmicutes were significantly different between the two groups. Bifidobacterium bombi (Actinobacteriota) and Candidatus_Schmidhempelia (Proteobacteria) were found to be important gut colonizer exclusive to NP and P group bees, respectively. DESeq2 analysis showed differentially abundant OTUs belonging to Lactobacillus spp. in each group. But for the differentially abundant detected OTUs, resolution till genus level was obtained which impairs our knowledge of the species associated with each group. Our data show that the gut microbiota between the groups differed when indoor-reared adult worker bees were exposed to different environments. The distinct gut microbiota between the two groups may also have been influenced by the different diets fed to bees upon segregation. Further studies can give important insights into the role of gut microbiota on bee health when indoor reared bees are employed for pollination.