Microbiome transplant and host genetic background shape Daphnia tolerance: Implications for ecological and ecotoxicological effect assessment

Abstract

Abstract Background Daphnia magna is a classic model in ecological, evolutionary, and ecotoxicological research. Despite global efforts to standardize cultures and experimental procedures, interclonal variability remains a limitation in interpreting and understanding responses to field and experimental conditions. Different microbiomes can lead to varying baseline responses of test organisms to stressors, making it challenging to distinguish between stressor-induced effects and inherent microbiome-driven variability. Here, we demonstrate that clone-specific microbiome composition is a significant part of the host tolerance to xenobiotics. Results To address the role of the gut microbiome in toxicity assessment, we developed a microbiota transplant approach and applied it to investigate how three D. magna clones respond to toxicity of hexavalent chromium. We found that interclonal variability in the lethality decreased in concert with the homogenization of taxonomic composition and metabolic capacity of the microbiome in the daphnid lines subjected to the microbiome transplant. Conclusion The microbiome was a primary driver of the host response to the toxicant; moreover, the direction of the response to the microbiome transplant was clone-dependent. In ecology and ecotoxicology, the microbiome transplantation approach can enhance the reproducibility of effect studies and robustness of ecological thresholds by limiting the confounding effect of microbiota composition. It also offers opportunities for research focused on how the microbiota shapes host physiology in health and disease.