#FEMSmicroBlog: About how pesticides affect the microbes in bee guts


Social bees — such as honey bees, bumble bees and stingless bees — are important pollinators for natural and agricultural plant communities. Unfortunately, some social bee species are currently in decline and pesticides are hypothesized to be contributing factors. The review “Pesticide-Induced Disturbances of Bee Gut Microbiota” published in FEMS Microbiology Reviews outlines the effects that pesticides have on microbial communities in bee guts. Michelle Hotchkiss explains for the #FEMSmicroBlog how pesticides disturb these communities and what this may mean for bee hosts. #FascinatingMicrobes


Bees and their microbes

When bees eat pollen and nectar, they often also take up environmental contaminants like pesticide residues. These residues can have negative impacts not only on the bees themselves but also on their gut microbiotas.

In the gut of social bees live five bacterial taxa that are highly adapted to their bee hosts and provide a range of host benefits (no, not honey making!). For example, bee gut microbes can stimulate the host immune system and protect it from pathogens and parasites. Therefore, pesticide-induced disturbances of such communities may have negative impacts on bee health and their performances.

Pesticide-induced disturbances of the bee gut microbiota may have negative impacts on bee health and performance.

The review “Pesticide-Induced Disturbances of Bee Gut Microbiotas” published in FEMS Microbiology Reviews explores the effects that pesticides can have on the microbes living in bee guts. The article discusses host and pesticide choice, how and what types of data were collected, which bacterial taxa are most affected by pesticides and what a disturbed gut microbiota means for bee host performance.


What do pesticide-induced microbial disturbances look like?

Beginning in the 1970s and intensifying in the past five years, scientists have focused on how different pesticides impact the community structure of bee gut microbiotas. The studies investigated both different pesticides and various bee host species.

How pesticides affect the bee gut microbiota.
Interactions between pesticides, the bee and its gut microbiota. From Hotchkiss et al. (2022).

The review summarizes how the abundance of each core gut microbe changes after bee hosts were exposed to pesticides. The three key parameters are: 1) how many pesticides can cause a change in abundance for that microbe, 2) the average direction of the change (i.e., increase or decrease) and 3) the extent of change.

Previous articles found that several pesticides cause small decreases in the abundance of two core bacterial taxa: Bifidobacteriales species and Lactobacillus species close to L. melliventris. On the other hand, other core bacteria, like Neisseriales and Bombilactobacillus species, are more resistant to pesticide-induced change.

Importantly, these changes in abundance can also vary based on pesticide dose, exposure duration and season. Additionally, pesticides can disturb gut microbes either by directly affecting the growth of microbes or by causing a decline in host health such that the host can no longer regulate its gut microbiota properly. Each of these two methods further determines the speed and consistency of its disturbances.


What does a pesticide-disturbed gut microbiota mean to a bee?

An important question in the field of pesticide-gut microbiota-host interactions is how pesticide-disturbed gut microbiota may impact host performance. So far, many studies have shown that a pesticide-disturbed bee gut microbiota is correlated with a decline in host performance. However, only one study provides strong evidence that a pesticide-disturbed gut microbiota causes a decline in host performance.

It is still not clear how pesticide-disturbed gut microbiota may impact bee performance.

Therefore, it is clear that multiple pesticides disturb the gut microbial communities of social bees. At the same time, we are just beginning to scratch the surface of what that means for bee host health and performance.


About the author of this blog

Michelle Hotchkiss is a PhD candidate at the University of Ottawa under the supervision of Drs. Jessica Forrest and Alexandre Poulain. She is interested in the symbiotic relationships between insects and their resident microbiotas. Currently, she is researching how fungicides and herbicides disturb the gut microbiotas of bumble bees, both during the colony growth stage and directly after hibernation. Besides research, Michelle is dedicated to using scientific outreach to educate the public about insect diversity and the importance of beneficial microbes to animal health.

About this blog section

The section #FascinatingMicrobes for the #FEMSmicroBlog explains the science behind a paper and highlights the significance and broader context of a recent finding. One of the main goals is to share the fascinating spectrum of microbes across all fields of microbiology.

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