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Date of Award

Spring 2021

Rights

Access restricted for 2 years to EWU users with an active EWU NetID

Date Available to Non-EWU Users

2023-06-11

Document Type

Thesis: EWU Only

Degree Name

Master of Science (MS) in Biology

Department

Biology

Abstract

Honey bees (Apis mellifera) are major pollinators of many food crops, but unfortunately, population declines are threatening global food security and ecosystem health. Honey bees are under multiple stressors, such as poor nutrition, parasitic mites, and pathogens. Similar to human health, the gut microbiome of the honey bee is hypothesized to affect bee’s overall health by supporting host metabolism and immune system. However, it’s not clear how stressors impact gut microbiome, and thus health, of bees. Nutritional supplementation could mitigate negative effects of stressors, particularly for bees that don’t have access to diverse floral resources. In this study, I conducted a one-year field experiment on 16 honey bee hives at two locations in eastern Washington to evaluate how nutritional supplementation impacts gut bacterial community structure and function, disease occurrence, and overall colony health. The supplementation was mixed in 1:1 sugar-water and mimicked nectar and pollen, consisting of protein, vitamins, and minerals. Control hives were fed 1:1 sugar-water only. To assess gut bacterial community structure before, during, and after feeding treatments, I used 16S rRNA gene amplicon sequencing on the Illumina MiSeq using primers 515F+barcode and 926R. The bioinformatic programs Quantitative Insights into Microbial Ecology (QIIME) and Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) were used to analyze how nutritional supplementation affected gut microbiome community structure and predicted function, respectively. Additionally, hives were weighed routinely to determine colony growth/productivity. For a subset of timepoints, I screened for Varroa mites and microsporidian pathogen Nosema. While supplemental nutrition did not have an overall impact on hive health or gut microbiome, the gut microbiome present at the beginning of experiment correlated with hive survival, suggesting presence/abundance of bacteria present before hives established may have a long-term impact on surviving stressors (i.e. overwintering). Additionally, the gut microbiome was significantly different between hives that survived and those that died at the timepoint before death, further suggesting the microbiome may play a role in hive survival. With further exploration of bacteria associated with survival (i.e. knockout or inoculation study), a probiotic mixture could be developed and examined for positive influence over hive survival.

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