Food quality effetcs on parasite-host interactions
Final Report Abstract
The results of this project suggest that parasite-host interactions are significantly affected by the availability of essential dietary resources, i.e. polyunsaturated fatty acids (PUFAs). Besides being indispensable structural components of cell membranes, PUFAs serve as precursors for eicosanoids, signalling molecules known to act on reproduction and immunity of both vertebrates and invertebrates. To explore the potential of dietary PUFAs to affect the course of parasitic infections, life history experiments were conducted using the freshwater herbivore Daphnia magna, different pathogenic microbes, and food sources differing in their PUFA composition. Results obtained with Pasteuria ramosa, a well-studied bacterial parasite of D. magna, indicate that both host and parasite can be affected by lipid-mediated food quality. Feeding on C20 PUFA-containing food sources resulted in higher offspring production of D. magna and these effects were conveyed to a great extent to the next generation (maternal effects). While feeding on a diet containing high PUFA concentrations significantly reduced the likelihood of becoming infected, the infection success in the next generation increased whenever the maternal diet contained PUFAs. We suggest that this opposing effect was caused by a trade-off between reproduction and immunity in the second generation. Experiments with an opportunistic bacterial pathogen (Pseudomonas sp.) showed that supplementation of a C20 PUFA-deficient diet with arachidonic acid (ARA) resulted in increased survival and reproduction of pathogen-challenged D. magna. This finding suggests that the observed benefit of consuming an ARA-rich diet during pathogen challenge is conveyed at least partially via ARA-derived eicosanoids. Quantitative real-time PCR analyses revealed that the beneficial effect of C20 PUFA-rich food on growth and reproduction is accompanied by an increased vitellogenin gene expression in D. magna. Moreover, vitellogenin expression was clearly induced upon parasite exposure, suggesting a possible involvement in pathogen recognition. In addition, genes involved in eicosanoid signalling were particularly influenced by dietary C20 PUFA availability. For example, the cyclooxygenase gene (Cox), coding for a central enzyme in the eicosanoid pathway, was highly responsive to both dietary C20 PUFA availability and parasite challenge, suggesting a role for prostanoid eicosanoids in reproduction and immunity of Daphnia. This project was one of the first assessing the physiological and ecological significance of dietary PUFAs for pathogen-challenged invertebrate hosts. We concluded that the dietary PUFA supply should receive increased attention in research on host-pathogen interactions and invertebrate disease models to better understand and predict disease dynamics in natural populations.
Publications
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(2012). The potential of dietary polyunsaturated fatty acids to modulate eicosanoid synthesis and reproduction in Daphnia magna: a gene expression approach. Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology 162: 449–454
Schlotz, N., Sørensen, J. G., and Martin-Creuzburg, D.
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(2013). Dietary supply with polyunsaturated fatty acids and resulting maternal effects influence host – parasite interactions. BMC Ecology 13: 41
Schlotz, N., Ebert, D., and Martin-Creuzburg, D.
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(2014). A dietary polyunsaturated fatty acid improves consumer performance during challenge with an opportunistic bacterial pathogen. FEMS Microbiology Ecology
Schlotz, N., Pester, M., Freese, H. M., and Martin-Creuzburg, D.
