Resistance and Vulnerability of Honeybee (Apis mellifera) Gut Bacteria to Commonly Used Pesticides

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Agricultural and apicultural practices expose honeybees to a range of pesticides that have the potential to negatively affect their physiology, neurobiology, and behavior. Accumulating evidence suggests that these effects extend to the honeybee gut microbiome, which serves important functions for honeybee health. Here we test the potential effects of the pesticides thiacloprid, acetamiprid, and oxalic acid on the gut microbiota of honeybees, first in direct in vitro inhibition assays and secondly in an in vivo caged bee experiment to test if exposure leads to gut microbiota community changes. We found that thiacloprid did not inhibit the honeybee core gut bacteria in vitro, nor did it affect overall community composition or richness in vivo. Acetamiprid did also not inhibit bacterial growth in vitro, but it did affect community structure within bees. The eight bacterial genera tested showed variable levels of susceptibility to oxalic acid in vitro. In vivo, treatment with this pesticide reduced amplicon sequence variant (ASV) richness and affected gut microbiome composition, with most marked impact on the common crop bacteria Lactobacillus kunkeei and the genus Bombella. We conducted network analyses which captured known associations between bacterial members and illustrated the sensitivity of the microbiome to environmental stressors. Our findings point to risks of honeybee exposure to oxalic acid, which has been deemed safe for use in treatment against Varroa mites in honeybee colonies, and we advocate for more extensive assessment of the long-term effects that it may have on honeybee health.

Original languageEnglish
Article number717990
JournalFrontiers in Microbiology
Number of pages16
Publication statusPublished - 2021

Bibliographical note

Funding Information:
We thank Philipp Engel for providing bacterial strains, Kasun H. Bodawatta for assistance in preparing samples for sequencing, and Suzanne Schmidt for ChemDraw structures included in Figure 1. Further, we thank the Social and Symbiotic Evolution Group for discussion of the project and for comments on the manuscript. Funding. This research was supported by a Ph.D. fellowship and research stipend from the Department of Biology, University of Copenhagen to VS and a European Research Council Consolidator Grant (771349) to MP.

Publisher Copyright:
© Copyright © 2021 Cuesta-Maté, Renelies-Hamilton, Kryger, Jensen, Sinotte and Poulsen.

    Research areas

  • acaricide, anthropogenic stressor, microbiome, neonicotinoid, social insect, symbiosis

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