The Effects Of Agrochemicals On The Gut Microbiota Of Honey Bees

Download or read book The Effects of Agrochemicals on the Gut Microbiota of Honey Bees written by Erick Vicente da Silva Motta and published by . This book was released on 2019 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: Honey bees are important environmental and agricultural pollinators whose populations have declined over the past decade. The reasons for this decline are not fully understood, but have been linked to environmental stressors, including poor nutrition, spread of pathogens and agrochemical exposure. Honey bees rely on a specialized gut microbiota for normal development, nutrition, and defense against pathogens. I hypothesized that environmental stressors could indirectly compromise bee health by affecting the gut microbiota. One environmental stressor that bees may often encounter is glyphosate, the primary herbicide used globally for weed control. Glyphosate inhibits an enzyme in the shikimate pathway found in all plants and most bacteria, but not in animals. Little is known about the effects of glyphosate on the gut microbiota of honey bees. In this dissertation, I discuss the effects of glyphosate on the gut microbiota and health of honey bees (Chapters 1, 2 and 3), and also talk about the effects of two other agrochemicals on the honey bee microbiota, the antibiotic tylosin (Chapter 2) and the insecticide imidacloprid (Appendix A). Chapter 1 focuses on understanding the acute effects of glyphosate on honey bee gut symbionts in vitro and in vivo. I demonstrate that most bee gut bacteria contain the enzyme targeted by glyphosate and vary in susceptibility depending on whether they possess a sensitive or insensitive version of the enzyme. I also show that glyphosate affects the gut microbiota of worker bees under laboratory conditions, by reducing the abundance of beneficial bacteria, such as Snodgrassella alvi. Chapter 2 compares the effects of chronic exposure of different concentrations of glyphosate or the antibiotic tylosin on honey bee workers before and after acquisition of the microbiota. I demonstrate that glyphosate affects the gut microbiota in a dose-dependent way, regardless of age or period of exposure, unlike tylosin whose effects are more prominent on bees treated with the antibiotic right after emergence. Chapter 3 investigates the effects of a commercial glyphosate-based herbicide formulation on the honey bee microbiome under field conditions. I show that a single treatment can affect the gut microbiota of bees randomly sampled from a hive and that perturbation is proportional to the level of exposure and persists at least one month after finishing treatment. These findings together suggest that honey bees treated with pure glyphosate or formulations containing glyphosate have their microbiota perturbed, under both laboratory and field conditions, with potential negative consequences for the host. Finally, I discuss the effects of the insecticide imidacloprid on the health and gut microbiota of honey bees (Appendix A) and describe the isolation and genome characterization of some bee gut-restricted Lactobacillus Firm-4 and Firm-5 (Appendix B)