Air pollution modifies key colonization factors of the beneficial bee gut symbiont Snodgrassella alvi and disrupts the bumblebee (Bombus terrestris) gut microbiome.

Air pollution is the worlds largest environmental health risk. Particulate pollutants, a major component of air pollution, are detrimental to human health and a significant risk to wildlife and ecosystems globally. Black carbon, a by-product of fossil fuel and biomass burning, is a key constituent of air pollution with levels continuing to increase worldwide. Here we describe the effects of black carbon on the beneficial gut microbiome of an important global insect pollinator, the buff-tailed bumblebee (Bombus terrestris). Our data shows that exposure to black carbon particulates alters the biofilm structure, gene expression and initial adhesion of beneficial bee gut coloniser, Snodgrassella alvi in vitro. Additionally, our results show that black carbon disrupts adult Bombus terrestris gut microbiome composition, a vital component to bee health. Exposure to black carbon increased bees viable gut bacteria and significantly altered the abundance of beneficial core bacteria Gilliamella and Bombilactobacillus in the microbiome. These findings demonstrate that exposure to black carbon air pollution has direct, measurable effects on bees beneficial gut commensal bacteria and microbiome. Together these data highlight that particulate pollutants are an underexplored risk for the health of insect pollinators.