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Paul Schmidhempel - One of the best experts on this subject based on the ideXlab platform.
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protein poor diet reduces host specific immune gene expression in bombus terrestris
Proceedings of The Royal Society B: Biological Sciences, 2014Co-Authors: Paul Schmidhempel, Franziska S. Brunner, Seth M. BarribeauAbstract:Parasites infect hosts non-randomly as genotypes of hosts vary in susceptibility to the same genotypes of parasites, but this specificity may be modulated by environmental factors such as nutrition. Nutrition plays an important role for any physiological investment. As immune responses are costly, resource limitation should negatively affect immunity through trade-offs with other physiological requirements. Consequently, nutritional limitation should diminish immune capacity in general, but does it also dampen differences among hosts? We investigated the effect of short-term pollen deprivation on the immune responses of our model host Bombus terrestris when infected with the highly prevalent natural parasite Crithidia bombi . Bumblebees deprived of pollen, their protein source, show reduced immune responses to infection. They failed to upregulate a number of genes, including antimicrobial peptides, in response to infection. In particular, they also showed less specific immune expression patterns across individuals and colonies. These findings provide evidence for how immune responses on the individual-level vary with important elements of the environment and illustrate how nutrition can functionally alter not only general resistance, but also alter the pattern of specific host–parasite interactions.
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qualitatively different immune response of the bumblebee host bombus terrestris to infection by different genotypes of the trypanosome gut parasite Crithidia bombi
Infection Genetics and Evolution, 2013Co-Authors: Seth M. Barribeau, Paul SchmidhempelAbstract:Abstract Insects have a complex and highly successful immune system that responds specifically to different types of parasites. Different genotypes of a parasite species can differ in infectivity and virulence; which is important for host-parasite co-evolutionary processes, such as antagonistic, fluctuating selection. Such coevolution obviously requires a genetic basis, but little is known about how hosts immunologically respond to different genotypes. The common European bumblebee Bombus terrestris is infected by the highly prevalent trypanosome gut parasite, Crithidia bombi. Here we examined expression of 26 immunological and metabolic genes in response to infection by two clones of C . bombi and compared that with exposure to injection with a bacterial challenge. Exposure to the two clones of C . bombi elicits qualitatively different immune expression responses. Interestingly, infection with one clone results in up regulation of AMP’s similar to bees given the bacterial challenge, while genes related to metabolism, signalling, and other effectors were similar between the two Crithidia exposures. Bees given different challenges were distinct enough to discern using linear discriminant analyses. We also found strong correlations, both positive and negative, among genes, which may shed light on how suites of genes are regulated and trade-offs in expression within this gene set.
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immune gene expression in bombus terrestris signatures of infection despite strong variation among populations colonies and sister workers
PLOS ONE, 2013Co-Authors: Franziska S. Brunner, Paul Schmidhempel, Seth M. BarribeauAbstract:Ecological immunology relies on variation in resistance to parasites. Colonies of the bumblebee Bombus terrestris vary in their susceptibility to the trypanosome gut parasite Crithidia bombi, which reduces colony fitness. To understand the possible origin of this variation in resistance we assayed the expression of 28 immunologically important genes in foraging workers. We deliberately included natural variation of the host “environment” by using bees from colonies collected in two locations and sampling active foraging workers that were not age controlled. Immune gene expression patterns in response to C. bombi showed remarkable variability even among genetically similar sisters. Nevertheless, expression varied with parasite exposure, among colonies and, perhaps surprisingly, strongly among populations (collection sites). While only the antimicrobial peptide abaecin is universally up regulated upon exposure, linear discriminant analysis suggests that the overall exposure effect is driven by a combination of several immune pathways and further immune functions such as ROS regulation. Also, the differences among colonies in their immune gene expression profiles provide clues to the mechanistic basis of well-known inter-colony variation in susceptibility to this parasite. Our results show that transcriptional responses to parasite exposure can be detected in ecologically heterogeneous groups despite strong background noise.
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probing mixed genotype infections i extraction and cloning of infections from hosts of the trypanosomatid Crithidia bombi
PLOS ONE, 2012Co-Authors: Rahel Salathe, Martina Tognazzo, Regula Schmidhempel, Paul SchmidhempelAbstract:We here present an efficient, precise and reliable method to isolate and cultivate healthy and viable single Crithidia bombi cells from bumblebee faeces using flow cytometry. We report a precision of >99% in obtaining single trypanosomatid cells for further culture and analysis (“cloning”). In the study, we have investigated the use of different liquid media to cultivate C. bombi and present an optimal medium for obtaining viable clones from all tested, infected host donors. We show that this method can be applied to genotype a collection of clones from natural infections. Furthermore, we show how to cryo-preserve C. bombi cells to be revived to become infective clones after at least 4 years of storage. Considering the high prevalence of infections in natural populations, our method provides a powerful tool in studying the level and diversity of these infections, and thus enriches the current methodology for the studies of complex host-parasite interactions.
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probing mixed genotype infections ii high multiplicity in natural infections of the trypanosomatid Crithidia bombi in its host bombus spp
PLOS ONE, 2012Co-Authors: Martina Tognazzo, Regula Schmidhempel, Paul SchmidhempelAbstract:Mixed-genotype infections have major consequences for many essential elements of host-parasite interactions. With genetic exchange between co-infecting parasite genotypes increased diversity among parasite offspring and the emergence of novel genotypes from infected hosts is possible. We here investigated mixed- genotype infections using the host, Bombus spp. and its trypanosome parasite Crithidia bombi as our study case. The natural infections of C. bombi were genotyped with a novel method for a representative sample of workers and spring queens in Switzerland. We found that around 60% of all infected hosts showed mixed-genotype infections with an average of 2.47±0.22 (S.E.) and 3.65±1.02 genotypes per worker or queen, respectively. Queens, however, harboured up to 29 different genotypes. Based on the genotypes of co-infecting strains, these could be putatively assigned to either ‘primary’ and ‘derived’ genotypes - the latter resulting from genetic exchange among the primary genotypes. High genetic relatedness among co-infecting derived but not primary genotypes supported this scenario. Co-infection in queens seems to be a major driver for the diversity of genotypes circulating in host populations.
Paul Schmid-hempel - One of the best experts on this subject based on the ideXlab platform.
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Genomic Variation among Strains of Crithidia bombi and C. expoeki
mSphere, 2019Co-Authors: Evgeny S. Gerasimov, Paul Schmid-hempel, Niklaus Zemp, Regula Schmid-hempel, Vyacheslav YurchenkoAbstract:In this study, we sequenced and analyzed the genomes of 40 strains, in addition to the already-reported two type strains, of two Crithidia species infecting bumblebees in Alaska and Central Europe and demonstrated that different strains of Crithidia bombi and C. expoeki vary considerably in terms of single nucleotide polymorphisms and gene copy number. Based on the genomic structure, phylogenetic analyses, and the pattern of copy number variation, we confirmed the status of C. expoeki as a separate species. The Alaskan populations appear to be clearly separated from those of Central Europe. This pattern fits a scenario of rapid host-parasite coevolution, where the selective advantage of a given parasite strain is only temporary. This study provides helpful insights into possible scenarios of selection and diversification of trypanosomatid parasites.IMPORTANCE A group of trypanosomatid flagellates includes several well-studied medically and economically important parasites of vertebrates and plants. Nevertheless, the vast majority of trypanosomatids infect only insects (mostly flies and true bugs) and, because of that, has attracted little research attention in the past. Of several hundred trypanosomatid species, only four can infect bees (honeybees and bumblebees). Because of such scarcity, these parasites are severely understudied. We analyzed whole-genome information for a total of 42 representatives of bee-infecting trypanosomatids collected in Central Europe and Alaska from a population genetics point of view. Our data shed light on the evolution, selection, and diversification in this important group of trypanosomatid parasites.
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The genomes of Crithidia bombi and C. expoeki, common parasites of bumblebees
2018Co-Authors: Paul Schmid-hempel, Seth M. Barribeau, Regula Schmid-hempel, Markus Aebi, Toshihiko Kitajima, Louis Du Plessis, Stefan ZollerAbstract:Trypanosomatids (Trypanosomatidae, Kinetoplastida) are flagellated protozoa containing many parasites of medical or agricultural importance. Among those, Crithidia bombi and C. expoeki, are common parasites in bumble bees around the world, and phylogenetically close to Leishmania and Leptomonas. They have a simple and direct life cycle with one host, and partially castrate the founding queens greatly reducing their fitness. Here, we report the nuclear genome sequences of one clone of each species, extracted from a field-collected infection. Using a combination of Roche 454 FLX Titanium, Pacific Biosciences PacBio RS, and Illumina GA2 instruments for C. bombi, and PacBio for C. expoeki, we could produce high-quality and well resolved sequences. We find that these genomes are around 32 and 34 MB, with 7,808 and 7,851 annotated genes for C. bombi and C. expoeki, respectively—which is somewhat less than reported from other trypanosomatids, with few introns, and organized in polycistronic units. A large fraction of genes received plausible functional support in comparison primarily with Leishmania and Trypanosoma. Comparing the annotated genes of the two species with those of six other trypanosomatids (C. fasciculata, L. pyrrhocoris, L. seymouri, B. ayalai, L. major, and T. brucei) shows similar gene repertoires and many orthologs. Similar to other trypanosomatids, we also find signs of concerted evolution in genes putatively involved in the interaction with the host, a high degree of synteny between C. bombi and C. expoeki, and considerable overlap with several other species in the set. A total of 86 orthologous gene groups show signatures of positive selection in the branch leading to the two Crithidia under study, mostly of unknown function. As an example, we examined the initiating glycosylation pathway of surface components in C. bombi, finding it deviates from most other eukaryotes and also from other kinetoplastids, which may indicate rapid evolution in the extracellular matrix that is involved in interactions with the host. Bumble bees are important pollinators and Crithidia-infections are suspected to cause substantial selection pressure on their host populations. These newly sequenced genomes provide tools that should help better understand host-parasite interactions in these pollinator pathogens.
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Experimental Evolution of a Trypanosome Parasite of Bumblebees and its Implications for Infection Success and Host Immune Response
Evolutionary Biology, 2016Co-Authors: Monika Marxer, Seth M. Barribeau, Paul Schmid-hempelAbstract:Selection on basic growth properties of parasites may have many consequences for parasite traits, infection outcome, or host responses to infection. It is known that genotypes (strains) of the trypanosome parasite of bumblebees Crithidia bombi vary widely in their growth rates in their natural host, Bombus terrestris , as well as when cultured in medium. To test for changes in growth rates and their consequences, we here experimentally evolved six strains of C. bombi for fast and slow growth under controlled conditions in culture medium. Subsequently, we infected the evolved lines in live host and found that lines selected for slow growth attained higher infection intensity in the live bumblebee than those evolved for fast growth, whilst the immune response of the host was the same to both kinds of lines. These results fit the expectation that attenuation through rapid adaptation to a different environment, the culture medium, makes the parasite less successful in its next host. Selection for fast growth therefore does not necessarily lead to higher parasite success or more transmission. Hence, insect trypanosome pathogens can be attenuated by experimental evolution in the culture; this could inform important aspects of host-parasite evolution and perhaps vaccine development.
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Insect antimicrobial peptides act synergistically to inhibit a trypanosome parasite.
Philosophical transactions of the Royal Society of London. Series B Biological sciences, 2016Co-Authors: Monika Marxer, Vera Vollenweider, Paul Schmid-hempelAbstract:The innate immune system provides protection from infection by producing essential effector molecules, such as antimicrobial peptides (AMPs) that possess broad-spectrum activity. This is also the case for bumblebees, Bombus terrestris, when infected by the trypanosome, Crithidia bombi Furthermore, the expressed mixture of AMPs varies with host genetic background and infecting parasite strain (genotype). Here, we used the fact that clones of C. bombi can be cultivated and kept as strains in medium to test the effect of various combinations of AMPs on the growth rate of the parasite. In particular, we used pairwise combinations and a range of physiological concentrations of three AMPs, namely Abaecin, Defensin and Hymenoptaecin, synthetized from the respective genomic sequences. We found that these AMPs indeed suppress the growth of eight different strains of C. bombi, and that combinations of AMPs were typically more effective than the use of a single AMP alone. Furthermore, the most effective combinations were rarely those consisting of maximum concentrations. In addition, the AMP combination treatments revealed parasite strain specificity, such that strains varied in their sensitivity towards the same mixtures. Hence, variable expression of AMPs could be an alternative strategy to combat highly variable infections.This article is part of the themed issue 'Evolutionary ecology of arthropod antimicrobial peptides'.
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Combining laboratory and field approaches to investigate the importance of flower nectar in the horizontal transmission of a bumblebee parasite
Entomologia Experimentalis et Applicata, 2014Co-Authors: Gabriel Cisarovsky, Paul Schmid-hempelAbstract:Knowledge of the complete life cycle of a parasite is crucial to understand the epidemiology and population dynamics of a disease. The populations of several social insect pollinators are decreasing, and parasites are often cited as a contributing factor. The exact transmission pathway of the bumblebee parasite Crithidia bombi (Lipa & Triggiani) (Kinetoplastea: Trypanosomatidae) between two hosts is still unknown, although a previous laboratory experiment suggests transmission via the nectar of flowers. Plant species may differentially protect or negatively affect the parasite while it resides in the flower, for instance if plants vary in their floral shape or the compounds present in their nectar. This will lead to differential transmission success and potentially influence disease epidemiology. In the present study we aimed at determining whether the parasite may indeed be transmitted in the nectar by the bumblebee Bombus terrestris (L.) (Hymenoptera: Apidae). We found that parasite survival was significantly decreased in water with higher sugar concentrations. However, none of the field-collected nectar samples contained parasite cells, and no parasite cells were transmitted between two artificial flowers by a foraging worker under laboratory conditions. Our results suggest instead that parasite cells may be deposited on flower surfaces and transported on worker surfaces.
Lynn S. Adler - One of the best experts on this subject based on the ideXlab platform.
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Effect of timing and exposure of sunflower pollen on a common gut pathogen of bumble bees
Ecological Entomology, 2019Co-Authors: George M. Locascio, Rebecca E. Irwin, River Pasquale, Eugene Amponsah, Lynn S. AdlerAbstract:1. Several bee species are declining due to multiple factors, including pathogens. Ingestion of sunflower (Helianthus annuus) pollen can dramatically reduce the bumble bee gut pathogen Crithidia bombi, but little is known about how timing and exposure to sunflower pollen consumption affects pathogen load. 2. Two experiments were carried out to investigate how exposure to sunflower pollen relative to pathogen exposure affects Crithidia bombi in Bombus impatiens. Foraging trials with pollen‐producing and male‐sterile (pollen absent) sunflower lines were performed to investigate whether sunflower pollen affected pathogen transmission in a single foraging bout, and 7‐day laboratory trials were done to investigate whether timing and duration of exposure to sunflower pollen after infection affected C. bombi. 3. In foraging trials, pollen presence on inflorescences inoculated with C. bombi did not affect transmission (pathogen cell counts of foraging workers) 1 week later, suggesting that a brief experience with sunflower pollen concurrent with pathogen exposure is insufficient to reduce infection. In laboratory trials, consuming sunflower pollen for the first 3.5 days or all 7 days after infection reduced cell counts compared with a negative control pollen, but consuming sunflower pollen starting 3.5 days after infection did not. Consuming sunflower pollen for 7 days was significantly and substantially more effective than any other treatment. Thus, both duration and timing of exposure to sunflower pollen may affect pathogen load. 4. These results are important for understanding ecological disease dynamics in natural settings with free‐flying bumble bees, and may inform decisions about using medicinal diets to manage bumble bee health commercially.
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README.R_Scripts from Pollen from multiple sunflower cultivars and species reduces a common bumblebee gut pathogen
2019Co-Authors: George M. Locascio, Luis Aguirre, Rebecca Irwin, Lynn S. AdlerAbstract:Pathogens are one of the factors driving pollinator declines. Diet can play an important role in mediating pollinator health and resistance to pathogens. Sunflower pollen (Helianthus annuus) dramatically reduced a gut pathogen (Crithidia bombi) of Bombus impatiens previously, but the breadth of this effect was unknown. We tested whether pollen from nine H. annuus cultivars, four wild H. annuus populations, H. petiolarus, H. argophyllus and two Solidago spp., reduced Crithidia in B. impatiens compared to mixed wildflower pollen and buckwheat pollen (Fagopyrum esculentum) as controls. We also compared hand- and honeybee-collected pollen (which contains nectar) to assess whether diet effects on pathogens were due to pollen or nectar. All Helianthus and Solidago pollen reduced Crithidia by 20–40-fold compared to buckwheat pollen, and all but three taxa reduced Crithidia compared to wildflower pollen. We found no consistent differences between hand- and bee-collected pollen, suggesting that pollen alone can reduce Crithidia infection. Our results indicate an important role of pollen diet for bee health and potentially broad options within the Asteraceae for pollinator plantings to manage bee disease
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README_CSV from Pollen from multiple sunflower cultivars and species reduces a common bumblebee gut pathogen
2019Co-Authors: George M. Locascio, Luis Aguirre, Rebecca Irwin, Lynn S. AdlerAbstract:Pathogens are one of the factors driving pollinator declines. Diet can play an important role in mediating pollinator health and resistance to pathogens. Sunflower pollen (Helianthus annuus) dramatically reduced a gut pathogen (Crithidia bombi) of Bombus impatiens previously, but the breadth of this effect was unknown. We tested whether pollen from nine H. annuus cultivars, four wild H. annuus populations, H. petiolarus, H. argophyllus and two Solidago spp., reduced Crithidia in B. impatiens compared to mixed wildflower pollen and buckwheat pollen (Fagopyrum esculentum) as controls. We also compared hand- and honeybee-collected pollen (which contains nectar) to assess whether diet effects on pathogens were due to pollen or nectar. All Helianthus and Solidago pollen reduced Crithidia by 20–40-fold compared to buckwheat pollen, and all but three taxa reduced Crithidia compared to wildflower pollen. We found no consistent differences between hand- and bee-collected pollen, suggesting that pollen alone can reduce Crithidia infection. Our results indicate an important role of pollen diet for bee health and potentially broad options within the Asteraceae for pollinator plantings to manage bee disease
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Death_by_Sflower from Pollen from multiple sunflower cultivars and species reduces a common bumblebee gut pathogen
2019Co-Authors: George M. Locascio, Luis Aguirre, Rebecca Irwin, Lynn S. AdlerAbstract:Pathogens are one of the factors driving pollinator declines. Diet can play an important role in mediating pollinator health and resistance to pathogens. Sunflower pollen (Helianthus annuus) dramatically reduced a gut pathogen (Crithidia bombi) of Bombus impatiens previously, but the breadth of this effect was unknown. We tested whether pollen from nine H. annuus cultivars, four wild H. annuus populations, H. petiolarus, H. argophyllus and two Solidago spp., reduced Crithidia in B. impatiens compared to mixed wildflower pollen and buckwheat pollen (Fagopyrum esculentum) as controls. We also compared hand- and honeybee-collected pollen (which contains nectar) to assess whether diet effects on pathogens were due to pollen or nectar. All Helianthus and Solidago pollen reduced Crithidia by 20–40-fold compared to buckwheat pollen, and all but three taxa reduced Crithidia compared to wildflower pollen. We found no consistent differences between hand- and bee-collected pollen, suggesting that pollen alone can reduce Crithidia infection. Our results indicate an important role of pollen diet for bee health and potentially broad options within the Asteraceae for pollinator plantings to manage bee disease
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Sflower1 from Pollen from multiple sunflower cultivars and species reduces a common bumblebee gut pathogen
2019Co-Authors: George M. Locascio, Luis Aguirre, Rebecca Irwin, Lynn S. AdlerAbstract:Pathogens are one of the factors driving pollinator declines. Diet can play an important role in mediating pollinator health and resistance to pathogens. Sunflower pollen (Helianthus annuus) dramatically reduced a gut pathogen (Crithidia bombi) of Bombus impatiens previously, but the breadth of this effect was unknown. We tested whether pollen from nine H. annuus cultivars, four wild H. annuus populations, H. petiolarus, H. argophyllus and two Solidago spp., reduced Crithidia in B. impatiens compared to mixed wildflower pollen and buckwheat pollen (Fagopyrum esculentum) as controls. We also compared hand- and honeybee-collected pollen (which contains nectar) to assess whether diet effects on pathogens were due to pollen or nectar. All Helianthus and Solidago pollen reduced Crithidia by 20–40-fold compared to buckwheat pollen, and all but three taxa reduced Crithidia compared to wildflower pollen. We found no consistent differences between hand- and bee-collected pollen, suggesting that pollen alone can reduce Crithidia infection. Our results indicate an important role of pollen diet for bee health and potentially broad options within the Asteraceae for pollinator plantings to manage bee disease
Evan C. Palmer-young - One of the best experts on this subject based on the ideXlab platform.
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Cross-infectivity of honey and bumble bee-associated parasites across three bee families.
Parasitology, 2020Co-Authors: Lyna Ngor, Evan C. Palmer-young, Rebecca E. Irwin, Rodrigo Burciaga Nevarez, Kaleigh A. Russell, Laura Leger, Sara June Giacomini, Mario S. Pinilla-gallego, Quinn S McfrederickAbstract:Recent declines of wild pollinators and infections in honey, bumble and other bee species have raised concerns about pathogen spillover from managed honey and bumble bees to other pollinators. Parasites of honey and bumble bees include trypanosomatids and microsporidia that often exhibit low host specificity, suggesting potential for spillover to co-occurring bees via shared floral resources. However, experimental tests of trypanosomatid and microsporidial cross-infectivity outside of managed honey and bumble bees are scarce. To characterize potential cross-infectivity of honey and bumble bee-associated parasites, we inoculated three trypanosomatids and one microsporidian into five potential hosts – including four managed species – from the apid, halictid and megachilid bee families. We found evidence of cross-infection by the trypanosomatids Crithidia bombi and C. mellificae, with evidence for replication in 3/5 and 3/4 host species, respectively. These include the first reports of experimental C. bombi infection in Megachile rotundata and Osmia lignaria, and C. mellificae infection in O. lignaria and Halictus ligatus. Although inability to control amounts inoculated in O. lignaria and H. ligatus hindered estimates of parasite replication, our findings suggest a broad host range in these trypanosomatids, and underscore the need to quantify disease-mediated threats of managed social bees to sympatric pollinators.
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Temperature dependence of parasitic infection and gut bacterial communities in bumble bees
Environmental microbiology, 2019Co-Authors: Evan C. Palmer-young, Thomas R Raffel, Lyna Ngor, Rodrigo Burciaga Nevarez, Jason A. Rothman, Quinn S McfrederickAbstract:High temperatures (e.g., fever) and gut microbiota can both influence host resistance to infection. However, effects of temperature-driven changes in gut microbiota on resistance to parasites remain unexplored. We examined the temperature dependence of infection and gut bacterial communities in bumble bees infected with the trypanosomatid parasite Crithidia bombi. Infection intensity decreased by over 80% between 21 and 37°C. Temperatures of peak infection were lower than predicted based on parasite growth in vitro, consistent with mismatches in thermal performance curves of hosts, parasites and gut symbionts. Gut bacterial community size and composition exhibited slight but significant, non-linear, and taxon-specific responses to temperature. Abundance of total gut bacteria and of Orbaceae, both negatively correlated with infection in previous studies, were positively correlated with infection here. Prevalence of the bee pathogen-containing family Enterobacteriaceae declined with temperature, suggesting that high temperature may confer protection against diverse gut pathogens. Our results indicate that resistance to infection reflects not only the temperature dependence of host and parasite performance, but also temperature-dependent activity of gut bacteria. The thermal ecology of gut parasite-symbiont interactions may be broadly relevant to infectious disease, both in ectothermic organisms that inhabit changing climates, and in endotherms that exhibit fever-based immunity.
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Medicinal value of sunflower pollen against bee pathogens
Scientific reports, 2018Co-Authors: Jonathan J Giacomini, Evan C. Palmer-young, Rebecca E. Irwin, Jessica M Leslie, David R. Tarpy, Lynn S. AdlerAbstract:Global declines in pollinators, including bees, can have major consequences for ecosystem services. Bees are dominant pollinators, making it imperative to mitigate declines. Pathogens are strongly implicated in the decline of native and honey bees. Diet affects bee immune responses, suggesting the potential for floral resources to provide natural resistance to pathogens. We discovered that sunflower (Helianthus annuus) pollen dramatically and consistently reduced a protozoan pathogen (Crithidia bombi) infection in bumble bees (Bombus impatiens) and also reduced a microsporidian pathogen (Nosema ceranae) of the European honey bee (Apis mellifera), indicating the potential for broad anti-parasitic effects. In a field survey, bumble bees from farms with more sunflower area had lower Crithidia infection rates. Given consistent effects of sunflower in reducing pathogens, planting sunflower in agroecosystems and native habitat may provide a simple solution to reduce disease and improve the health of economically and ecologically important pollinators.
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Pollen extracts and constituent sugars increase growth of a trypanosomatid parasite of bumble bees.
PeerJ, 2017Co-Authors: Evan C. Palmer-young, Lucy ThursfieldAbstract:: Phytochemicals produced by plants, including at flowers, function in protection against plant diseases, and have a long history of use against trypanosomatid infection. Floral nectar and pollen, the sole food sources for many species of insect pollinators, contain phytochemicals that have been shown to reduce trypanosomatid infection in bumble and honey bees when fed as isolated compounds. Nectar and pollen, however, consist of phytochemical mixtures, which can have greater antimicrobial activity than do single compounds. This study tested the hypothesis that pollen extracts would inhibit parasite growth. Extracts of six different pollens were tested for direct inhibitory activity against cell cultures of the bumble bee trypanosomatid gut parasite Crithidia bombi. Surprisingly, pollen extracts increased parasite growth rather than inhibiting it. Pollen extracts contained high concentrations of sugars, mainly the monosaccharides glucose and fructose. Experimental manipulations of growth media showed that supplemental monosaccharides (glucose and fructose) increased maximum cell density, while a common floral phytochemical (caffeic acid) with inhibitory activity against other trypanosomatids had only weak inhibitory effects on Crithidia bombi. These results indicate that, although pollen is essential for bees and other pollinators, pollen may promote growth of intestinal parasites that are uninhibited by pollen phytochemicals and, as a result, can benefit from the nutrients that pollen provides.
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Synergistic effects of floral phytochemicals against a bumble bee parasite.
Ecology and evolution, 2017Co-Authors: Evan C. Palmer-young, Ben M Sadd, Rebecca E. Irwin, Lynn S. AdlerAbstract:Floral landscapes comprise diverse phytochemical combinations. Individual phytochemicals in floral nectar and pollen can reduce infection in bees and directly inhibit trypanosome parasites. However, gut parasites of generalist pollinators, which consume nectar and pollen from many plant species, are exposed to phytochemical combinations. Interactions between phytochemicals could augment or decrease effects of single compounds on parasites. Using a matrix of 36 phytochemical treatment combinations, we assessed the combined effects of two floral phytochemicals, eugenol and thymol, against four strains of the bumblebee gut trypanosome Crithidia bombi. Eugenol and thymol had synergistic effects against C. bombi growth across seven independent experiments, showing that the phytochemical combination can disproportionately inhibit parasites. The strength of synergistic effects varied across strains and experiments. Thus, the antiparasitic effects of individual compounds will depend on both the presence of other phytochemicals and parasite strain identity. The presence of synergistic phytochemical combinations could augment the antiparasitic activity of individual compounds for pollinators in diverse floral landscapes.
Rebecca E. Irwin - One of the best experts on this subject based on the ideXlab platform.
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Cross-infectivity of honey and bumble bee-associated parasites across three bee families.
Parasitology, 2020Co-Authors: Lyna Ngor, Evan C. Palmer-young, Rebecca E. Irwin, Rodrigo Burciaga Nevarez, Kaleigh A. Russell, Laura Leger, Sara June Giacomini, Mario S. Pinilla-gallego, Quinn S McfrederickAbstract:Recent declines of wild pollinators and infections in honey, bumble and other bee species have raised concerns about pathogen spillover from managed honey and bumble bees to other pollinators. Parasites of honey and bumble bees include trypanosomatids and microsporidia that often exhibit low host specificity, suggesting potential for spillover to co-occurring bees via shared floral resources. However, experimental tests of trypanosomatid and microsporidial cross-infectivity outside of managed honey and bumble bees are scarce. To characterize potential cross-infectivity of honey and bumble bee-associated parasites, we inoculated three trypanosomatids and one microsporidian into five potential hosts – including four managed species – from the apid, halictid and megachilid bee families. We found evidence of cross-infection by the trypanosomatids Crithidia bombi and C. mellificae, with evidence for replication in 3/5 and 3/4 host species, respectively. These include the first reports of experimental C. bombi infection in Megachile rotundata and Osmia lignaria, and C. mellificae infection in O. lignaria and Halictus ligatus. Although inability to control amounts inoculated in O. lignaria and H. ligatus hindered estimates of parasite replication, our findings suggest a broad host range in these trypanosomatids, and underscore the need to quantify disease-mediated threats of managed social bees to sympatric pollinators.
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Effect of timing and exposure of sunflower pollen on a common gut pathogen of bumble bees
Ecological Entomology, 2019Co-Authors: George M. Locascio, Rebecca E. Irwin, River Pasquale, Eugene Amponsah, Lynn S. AdlerAbstract:1. Several bee species are declining due to multiple factors, including pathogens. Ingestion of sunflower (Helianthus annuus) pollen can dramatically reduce the bumble bee gut pathogen Crithidia bombi, but little is known about how timing and exposure to sunflower pollen consumption affects pathogen load. 2. Two experiments were carried out to investigate how exposure to sunflower pollen relative to pathogen exposure affects Crithidia bombi in Bombus impatiens. Foraging trials with pollen‐producing and male‐sterile (pollen absent) sunflower lines were performed to investigate whether sunflower pollen affected pathogen transmission in a single foraging bout, and 7‐day laboratory trials were done to investigate whether timing and duration of exposure to sunflower pollen after infection affected C. bombi. 3. In foraging trials, pollen presence on inflorescences inoculated with C. bombi did not affect transmission (pathogen cell counts of foraging workers) 1 week later, suggesting that a brief experience with sunflower pollen concurrent with pathogen exposure is insufficient to reduce infection. In laboratory trials, consuming sunflower pollen for the first 3.5 days or all 7 days after infection reduced cell counts compared with a negative control pollen, but consuming sunflower pollen starting 3.5 days after infection did not. Consuming sunflower pollen for 7 days was significantly and substantially more effective than any other treatment. Thus, both duration and timing of exposure to sunflower pollen may affect pathogen load. 4. These results are important for understanding ecological disease dynamics in natural settings with free‐flying bumble bees, and may inform decisions about using medicinal diets to manage bumble bee health commercially.
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Bee pathogen transmission dynamics: deposition, persistence and acquisition on flowers.
Proceedings. Biological sciences, 2019Co-Authors: Laura L. Figueroa, Cali Grincavitch, Rebecca E. Irwin, Malcolm Blinder, Angus Jelinek, Emilia K Mann, Liam A Merva, Lucy E Metz, Amy Y Zhao, Scott H. McartAbstract:Infectious diseases are a primary driver of bee decline worldwide, but limited understanding of how pathogens are transmitted hampers effective management. Flowers have been implicated as hubs of bee disease transmission, but we know little about how interspecific floral variation affects transmission dynamics. Using bumblebees ( Bombus impatiens), a trypanosomatid pathogen ( Crithidia bombi) and three plant species varying in floral morphology, we assessed how host infection and plant species affect pathogen deposition on flowers, and plant species and flower parts impact pathogen survival and acquisition at flowers. We found that host infection with Crithidia increased defaecation rates on flowers, and that bees deposited faeces onto bracts of Lobelia siphilitica and Lythrum salicaria more frequently than onto Monarda didyma bracts . Among flower parts, bracts were associated with the lowest pathogen survival but highest resulting infection intensity in bee hosts. Additionally, we found that Crithidia survival across flower parts was reduced with sun exposure. These results suggest that efficiency of pathogen transmission depends on where deposition occurs and the timing and place of acquisition, which varies among plant species and environmental conditions. This information could be used for development of wildflower mixes that maximize forage while minimizing disease spread.
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Medicinal value of sunflower pollen against bee pathogens
Scientific reports, 2018Co-Authors: Jonathan J Giacomini, Evan C. Palmer-young, Rebecca E. Irwin, Jessica M Leslie, David R. Tarpy, Lynn S. AdlerAbstract:Global declines in pollinators, including bees, can have major consequences for ecosystem services. Bees are dominant pollinators, making it imperative to mitigate declines. Pathogens are strongly implicated in the decline of native and honey bees. Diet affects bee immune responses, suggesting the potential for floral resources to provide natural resistance to pathogens. We discovered that sunflower (Helianthus annuus) pollen dramatically and consistently reduced a protozoan pathogen (Crithidia bombi) infection in bumble bees (Bombus impatiens) and also reduced a microsporidian pathogen (Nosema ceranae) of the European honey bee (Apis mellifera), indicating the potential for broad anti-parasitic effects. In a field survey, bumble bees from farms with more sunflower area had lower Crithidia infection rates. Given consistent effects of sunflower in reducing pathogens, planting sunflower in agroecosystems and native habitat may provide a simple solution to reduce disease and improve the health of economically and ecologically important pollinators.
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Synergistic effects of floral phytochemicals against a bumble bee parasite.
Ecology and evolution, 2017Co-Authors: Evan C. Palmer-young, Ben M Sadd, Rebecca E. Irwin, Lynn S. AdlerAbstract:Floral landscapes comprise diverse phytochemical combinations. Individual phytochemicals in floral nectar and pollen can reduce infection in bees and directly inhibit trypanosome parasites. However, gut parasites of generalist pollinators, which consume nectar and pollen from many plant species, are exposed to phytochemical combinations. Interactions between phytochemicals could augment or decrease effects of single compounds on parasites. Using a matrix of 36 phytochemical treatment combinations, we assessed the combined effects of two floral phytochemicals, eugenol and thymol, against four strains of the bumblebee gut trypanosome Crithidia bombi. Eugenol and thymol had synergistic effects against C. bombi growth across seven independent experiments, showing that the phytochemical combination can disproportionately inhibit parasites. The strength of synergistic effects varied across strains and experiments. Thus, the antiparasitic effects of individual compounds will depend on both the presence of other phytochemicals and parasite strain identity. The presence of synergistic phytochemical combinations could augment the antiparasitic activity of individual compounds for pollinators in diverse floral landscapes.