There has been a growing concern about the worldwide decline in certain insects. The declining honey bee population is of particular concern due to their global role as pollinators of flowering plants, including many crops. Their increased mortality is thought to be due to several factors including habitat loss through deforestation, agricultural expansion and industrialization, but the overall drastic decline in bee numbers is not fully understood (see previous PLoSibilities posts, “To Bee or not to Bee” and “The plight of the honey bee” ). A new study posits an interesting new theory that could explain more about the collapse of the honey bees.
Herbicides are a type of pesticide used to control unwanted vegetation. Glyphosate is a commonly used herbicide. Glyphosate specifically targets the enzyme, enolpyruvylshikimate-3-phosphate synthase (EPSPS), which is only found in plants and microorganisms; therefore, most animals and insects should not be affected by glyphosate. But just like humans, honey bees rely on microorganisms in their guts to keep them healthy. For this reason, glyphosate may indirectly harm honey bees by targeting their gut bacteria.
In this study, researchers investigated the bacteria that live in honey bee guts to determine whether they are sensitive to glyphosate. They began by examining the eight main types of bacteria found in the honey bee gut. They found that all of these bacteria had the EPSPS gene, meaning that they could be killed by glyphosate. Importantly, they observed that doses of glyphosate at levels equivalent to environmental levels reduced the amount of healthy gut bacteria in honey bees and left them susceptible to the opportunistic pathogen Serratia marcescens.
This research highlights a potential role of glyphosate in colony decline and illustrates the importance of microorganisms in the overall health of our ecosystem. This research also highlights a potential solution to improve the health of honey bees. Farmers heavily depend on healthy bees to pollinate their flowering crops, so reduced use of glyphosate could improve the health of their bee colonies and crops alike. Future studies will investigate correlations between honey bee decline with the levels of glyphosate found in that particular area.
Summary written by: Emma Price
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Glyphosate perturbs the gut microbiota of honey bees