Microbiome mediated tolerance to biotic stressors: a case study of the interaction between a toxic cyanobacterium and an oomycete-like infection in Daphnia magna

Abstract

Studies on stressor responses are often performed in controlled laboratory settings. The microbial communities in laboratory settings often differ from the natural environment, which could ultimately be reflected in different stress responses. In this study, we investigated the impact of single versus simultaneous multiple stressor exposure on Daphnia magna life history traits and whether this tolerance was microbiome-mediated. Daphnia individuals were exposed to the toxic cyanobacterium Microcystis aeruginosa and a fungal infection, Aspergillus aculeatus like type. Three genotypes were included to investigate genotype-specific responses. Survival, reproduction and body size were monitored for three weeks and gut microbial communities were sampled and characterized at the end of the experiment. Our study shows survival in Daphnia was microbiome-mediated as survival was only negatively impacted when Daphnia received a lab microbial community. Daphnia which received a natural microbial community have a broader environmental pool of microbiota to randomnly and selectively take up and showed no negative impact on survival. Simultaneous exposure to both stressors also revealed an antagonistic interaction for survival. Fecundity and body size were negatively impacted by exposure to stress, however, responses were here not microbiome-mediated. In addition, genotype specific responses were detected for survival and fecundity, which could be linked with the selective capabilities of the Daphnia genotypes to select beneficial or neutral microbial stains from the environment.