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Open Access Publications from the University of California

Scholarly Works (27 results)

  • Article
  • Peer Reviewed
Mester, Volume 33 (2004)
[No abstract]
    Cover page: Second Language Acquisition, Bilingualism and Identity: An Interview with Merrill Swain.
    • Thesis
    • Peer Reviewed
    UC Riverside Electronic Theses and Dissertations (2019)

    Bees are important insect pollinators in both agricultural and natural settings who may encounter toxicants while foraging on plants growing in contaminated soils. How these chemicals affect the bee microbiome, which confers many health benefits to the host, is an important but understudied aspect of pollinator health. Through a combination of 16S rRNA gene sequencing, LC-MS metabolomics, ICP-OES spectroscopy, quantitative PCR, culturing, microbiome manipulation, and whole organism exposure studies, I attempt to establish the effects that toxicants have on social bees and their associated microbes.

    The microbiome of animals has been shown to reduce metalloid toxicity, so I exposed microbiome-inoculated or uninoculated bumble bees to 0.75 mg/L selenate and found that inoculated bees survive longer when compared to uninoculated bees. I also showed that selenate exposure altered the composition of the bumble bee microbiome and that the growth of two major gut symbionts – Snodgrassella alvi and Lactobacillus bombicola – was unaffected by this exposure.

    Due to the pervasiveness of environmental pollution in bee habitats, I exposed bumble bees to cadmium, copper, selenate, imidacloprid, and hydrogen peroxide and found that each of these compounds can be lethal to bees. I also showed that most of these chemicals can affect the diversity of the bee microbiome and that there is interstrain variation in toxicant tolerance genes in the major bee symbionts Snodgrassella alvi and Gilliamella apicola.

    As exposure to cadmium or selenate has been shown to affect animal-associated microbes, I assayed the effects of these chemicals on honey bees and observed shifts in the bee microbiome at multiple timepoints. I also found that exposure to selenate and cadmium changes the overall bee metabolome and may cause oxidative damage to proteins and lipids. Lastly, I found that bee-associated bacteria can bioaccumulate cadmium but generally not selenate.

    In this dissertation I demonstrated that bee-associated bacteria are generally robust to toxicant exposure, but that chemicals can alter the composition of both bumble bee and honey bee microbiomes. I also show that toxicants affect bee metabolism, and that the bee microbiome plays an important role in maintaining host health when challenged with toxicants.

      Cover page: Effects of Toxicant Exposure on Honey Bee and Bumble Bee Microbiomes and Impacts on Host Health
      • Article
      • Peer Reviewed
      UC Irvine Previously Published Works (2022)
      Tobamoviruses are agriculturally relevant viruses that cause crop losses and have infected plants in many regions of the world. These viruses are frequently found in municipal wastewater, likely coming from human diet and industrial waste across wastewater catchment areas. As part of a large wastewater-based epidemiology study across Southern California, we analyzed RNA sequence data from 275 influent wastewater samples obtained from eight wastewater treatment plants with a catchment area of approximately 16 million people from July 2020 to August 2021. We assembled 1,083 high-quality genomes, enumerated viral sequencing reads, and detected thousands of single nucleotide variants from eight common tobamoviruses: bell pepper mottle virus, cucumber green mottle mosaic virus, pepper mild mottle virus, tobacco mild green mosaic virus, tomato brown rugose fruit virus, tomato mosaic virus, tomato mottle mosaic virus, and tropical soda apple mosaic virus. We show that single nucleotide variants had amino acid-altering consequences along with synonymous mutations, which represents potential evolution with functional consequences in genomes of these viruses. Our study shows the importance of wastewater sequencing to monitor the genomic diversity of these plant-infecting viruses, and we suggest that our data could be used to continue tracking the genomic variability of such pathogens. IMPORTANCE Diseases caused by viruses in the genus Tobamovirus cause crop losses around the world. As with other viruses, mutation occurring in the virus's genomes can have functional consequences and may alter viral infectivity. Many of these plant-infecting viruses have been found in wastewater, likely coming from human consumption of infected plants and produce. By sequencing RNA extracted from influent wastewater obtained from eight wastewater treatment plants in Southern California, we assembled high-quality viral genomes and detected thousands of single nucleotide variants from eight tobamoviruses. Our study shows that Tobamovirus genomes vary at many positions, which may have important consequences when designing assays for the detection of these viruses by agricultural or environmental scientists.
        Cover page: Sequencing and Variant Detection of Eight Abundant Plant-Infecting Tobamoviruses across Southern California Wastewater
        • Article
        • Peer Reviewed
        UC Irvine Previously Published Works (2018)
          Cover page: Floral and Foliar Source Affect the Bee Nest Microbial Community
          • Article
          • Peer Reviewed
          UC Riverside Previously Published Works (2020)
          Mounting evidence suggests that microbes found in the pollen provisions of wild and solitary bees are important drivers of larval development. As these microbes are also known to be transmitted via the environment, most likely from flowers, the diet breadth of a bee may affect the diversity and identity of the microbes that occur in its pollen provisions. Here, we tested the hypothesis that, due to the importance of floral transmission of microbes, diet breadth affects pollen provision microbial community composition. We collected pollen provisions at four sites from the polylectic bee Osmia lignaria and the oligolectic bee Osmia ribifloris. We used high-throughput sequencing of the bacterial 16S rRNA gene to characterize the bacteria found in these provisions. We found minimal overlap in the specific bacterial variants in pollen provisions across the host species, even when the bees were constrained to foraging from the same flowers in cages at one site. Similarly, there was minimal overlap in the specific bacterial variants across sites, even within the same host species. Together, these findings highlight the importance of environmental transmission and host specific sorting influenced by diet breadth for microbes found in pollen provisions. Future studies addressing the functional consequences of this filtering, along with tests for differences between more species of oligoletic and polylectic bees will provide rich insights into the microbial ecology of solitary bees.
            Cover page: Diet Breadth Affects Bacterial Identity but Not Diversity in the Pollen Provisions of Closely Related Polylectic and Oligolectic Bees.
            • Article
            • Peer Reviewed
            UC Irvine Previously Published Works (2019)
              Cover page: Cadmium and Selenate Exposure Affects the Honey Bee Microbiome and Metabolome, and Bee-Associated Bacteria Show Potential for Bioaccumulation
              • Article
              • Peer Reviewed
              UC Riverside Previously Published Works (2021)
              Invasive species present a worldwide concern as competition and pathogen reservoirs for native species. Specifically, the invasive social wasp, Vespula pensylvanica, is native to western North America and has become naturalized in Hawaii, where it exerts pressures on native arthropod communities as a competitor and predator. As invasive species may alter the microbial and disease ecology of their introduced ranges, there is a need to understand the microbiomes and virology of social wasps. We used 16S rRNA gene sequencing to characterize the microbiome of V. pensylvanica samples pooled by colony across two geographically distinct ranges and found that wasps generally associate with taxa within the bacterial genera Fructobacillus, Fructilactobacillus, Lactococcus, Leuconostoc, and Zymobacter, and likely associate with environmentally-acquired bacteria. Furthermore, V. pensylvanica harbors-and in some cases were dominated by-many endosymbionts including Wolbachia, Sodalis, Arsenophonus, and Rickettsia, and were found to contain bee-associated taxa, likely due to scavenging on or predation upon honey bees. Next, we used reverse-transcriptase quantitative PCR to assay colony-level infection intensity for Moku virus (family: Iflaviridae), a recently-described disease that is known to infect multiple Hymenopteran species. While Moku virus was prevalent and in high titer, it did not associate with microbial diversity, indicating that the microbiome may not directly interact with Moku virus in V. pensylvanica in meaningful ways. Collectively, our results suggest that the invasive social wasp V. pensylvanica associates with a simple microbiome, may be infected with putative endosymbionts, likely acquires bacterial taxa from the environment and diet, and is often infected with Moku virus. Our results suggest that V. pensylvanica, like other invasive social insects, has the potential to act as a reservoir for bacteria pathogenic to other pollinators, though this requires experimental demonstration.
                Cover page: Microbiome of the wasp Vespula pensylvanica in native and invasive populations, and associations with Moku virus.
                • Article
                • Peer Reviewed
                UC Irvine Previously Published Works (2019)
                  Cover page: The bumble bee microbiome increases survival of bees exposed to selenate toxicity
                  • Article
                  • Peer Reviewed
                  UC Riverside Previously Published Works (2017)
                  Many countries are utilizing reclaimed wastewater for agriculture because drought, rising temperatures, and expanding human populations are increasing water demands. Unfortunately, wastewater often contains biologically active, pseudopersistent pharmaceuticals, even after treatment. Runoff from farms and output from wastewater treatment plants also contribute high concentrations of pharmaceuticals to the environment. This study assessed the effects of common pharmaceuticals on an agricultural pest, Trichoplusia ni (Lepidoptera: Noctuidae). Larvae were reared on artificial diets spiked with contaminants of emerging concern (CECs) at environmentally relevant concentrations. Trichoplusia ni showed increased developmental time and mortality when reared on artificial diets containing antibiotics, hormones, or a mixture of contaminants. Mortality was also increased when T. ni were reared on tomatoes grown hydroponically with the same concentrations of antibiotics. The antibiotic-treated plants translocated ciprofloxacin through their tissues to roots, shoots, and leaves. Microbial communities of T. ni changed substantially between developmental stages and when exposed to CECs in their diets. Our results suggest that use of reclaimed wastewater for irrigation of crops can affect the developmental biology and microbial communities of an insect of agricultural importance.
                    Cover page: Contaminants of emerging concern affect Trichoplusia ni growth and development on artificial diets and a key host plant.
                    • Article
                    • Peer Reviewed
                    UC Irvine Previously Published Works (2018)
                      Cover page: Longitudinal Effects of Supplemental Forage on the Honey Bee (Apis mellifera) Microbiota and Inter- and Intra-Colony Variability
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