Diesel exhaust particles alter gut microbiome and gene expression in the
bumblebee Bombus terrestris
Abstract
Insect decline is a major threat for ecosystems around the world as they
provide many important functions, such as pollination or pest control.
Pollution is one of the main reasons for the decline, besides changes in
land use, global warming, and invasive species. While negative impacts
of pesticides are well studied, there is still a lack of knowledge about
the effects of other anthropogenic pollutants, such as airborne
particulate matter, on insects. To address this, we exposed workers of
the bumblebee Bombus terrestris to sublethal doses of diesel exhaust
particles (DEPs) and brake dust, orally or via air. After seven days, we
looked at the composition of the gut microbiome and tracked changes in
gene expression. While there were no changes in the other treatments,
oral DEP exposure significantly altered the structure of the gut
microbiome. In particular, the core bacterium Snodgrassella had a
decreased abundance in the DEP treatment. Similarly, transcriptome
analysis revealed changes in gene expression after oral DEP exposure,
but not in the other treatments. The changes are related to metabolism
and signal transduction which indicates a general stress response. Taken
together, our results suggest potential health effects of DEP exposure
on insects, here shown in bumblebees, as gut dysbiosis may increase the
susceptibility of bumblebees to pathogens, while a general stress
response may lower available energy resources. However, experiments with
multiple stressors and on colony level are needed to provide a more
comprehensive understanding of the impact of DEPs on insects.