Browsing by Subject "Honey bee"
Now showing 1 - 4 of 4
- Results Per Page
- Sort Options
Item Behavioral and molecular mechanisms of pheromone transmission in the honey bee (Apis mellifera)(2017-08) Ma, Rong, Ph. D.; Mueller, Ulrich G.; Hofmann, Johann; Gilbert, Lawrence E; Jha, Shalene; Grozinger, Christina MThe European honey bee (Apis mellifera) has a sophisticated system of pheromonal signals that mediate a wide range of behaviors important for their fitness, including reproductive dominance, nest defense, and cooperative brood care. In honey bees, there are two distinct pheromones emitted by larvae, brood pheromone and (E)-beta-ocimene. By integrating behavior, chemical ecology, and transcriptomics, this dissertation analyzes several key stages in signal transmission in a systematic effort to understand how these two pheromones affect behavior, and in the process, generates a synthetic understanding of a highly complex system of communication. Previous studies have explored behavioral and gene expression patterns related to honey bee pheromones; however, none have compared the roles that two divergent pheromones from a common source play in rapid regulation of foraging behavior. Furthermore, while previous studies have investigated the mechanisms of pheromone detection and the factors involved in regulation of foraging behavior, it remains unclear how individual responses to pheromone exposure scales to colony-level changes in behavior. By investigating the behavioral, physiological, and genomic influences of honey bee chemical communication, this dissertation links phenotypic plasticity in behavior to gene expression profiles in the brain and provides insights into the evolution of a sophisticated chemical language.Item Morphometrics of the dwarf honey bee Apis florea show biogeographic differentiation across India(2017-12-08) Herman, Jacob John; Mueller, Ulrich G.; Linder, Craig RThe Asian dwarf honey bee (Apis florea) is a relatively small honey bee, nests in the open with single combs attached to tree branches, and inhabits areas uninhabitable to other Apis species. A. florea is one of few honey bees in the genus to have remained unmanaged by beekeepers across Asia. Because A. florea has not been bred for specific traits or transported intentionally across continents like managed Apis species, populations of A. florea should offer insight into natural adaptations of honey bee populations to diverse climates. We use morphometrics to examine which environmental factors correlate with morphological differences between populations of A. florea surveyed across India. The surveyed populations show a trend of increased wing size going from the equator to the north. The populations also vary in Cubital Index, a wing venation measurement often associated with subspecies differentiation, and this variation is correlated with minimum temperature of the coldest month. Taken together, these findings show that A. florea differs morphologically across a temperature gradient in India and support future work towards understanding biogeographic patterns in this understudied species of honey bee.Item The effects of agrochemicals on the gut microbiota of honey bees(2019-09-17) da Silva Motta, Erick Vicente; Moran, Nancy A., Ph. D.; Mehdy, Mona; Barrick, Jeffrey; Havird, Justin; Jha, ShaleneHoney 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).Item Type VI secretion system-mediated antagonism in the honey bee gut microbiota(2020-04-14) Steele, Margaret Irene; Moran, Nancy A., Ph. D.; Whiteley, Marvin; Davies, Bryan; Barrick, Jeffrey E.; Cenik, CanGram-negative bacteria, including animal symbionts, often use type VI secretion systems (T6SSs) to inject toxins into nearby competitors. The honey bee gut microbiota consists of a small number of highly coevolved species, which may use T6SSs to interact competitively with one another and with pathogens. This dissertation explores the diversity, evolution, and function of T6SSs and associated toxins in the bee gut. Chapter 1 identifies genes encoding two T6SSs in bee symbiont Snodgrassella alvi, which are more highly expressed in the bee gut. S. alvi strains encoding Sa-T6SS-1 also encode many Rhs toxin genes, which have been horizontally transferred between S. alvi and co-occurring symbiont Gilliamella apicola. These toxins diversify through recombination, or “C-terminal displacement,” resulting in long arrays of orphaned 3 ends, which lack secretion domains, but are expressed and encode functional proteins. Chapter 2 provides a broader perspective on the diversity and evolution of T6SSs within bee gut symbionts, which have co-diversified with each other and their hosts for more than 80 million years. A survey of 198 isolate genomes identified 5 unique T6SS loci, which are likely to have been present within the microbiota of the common ancestor of social bees, and revealed that co-occurring species have adopted different strategies for toxin diversification. Furthermore, S. alvi uses a T6SS to antagonize a wide range of bee gut symbionts. Chapter 3 shows that opportunistic pathogen Serratia marcescens is rapidly eliminated from the guts of bees with a conventional gut microbiota, an effect which is not fully attributable to any single gut symbiont. From microscopy images, S. alvi may also serve as a physical barrier against invasion. S. marcescens encodes a T6SS used to antagonize E. coli and other S. marcescens strains, but not bee gut isolates, and T6SSs appear not to benefit S. marcescens in the bee gut. Together, these findings indicate that multiple bee gut symbionts engage in T6SS-mediated antagonism using conserved T6SSs and diverse toxins. An opportunistic pathogen is excluded, regardless of whether or not it has a T6SS, suggesting that coevolution may be important for effective antagonism.