Meeting Abstract
Eugregarines are protozoan members of the microbiome present in a wide variety of insect hosts. Emerging evidence suggests that their presence can modulate the outcome of subsequent infection with other parasites, but it is still an open question as to whether gregarines interact with other microbes through competition for resources or through stimulating cross-reactive immune responses. In this study, we used qPCR to quantify variation in the immunological dynamics of lab and wild populations of flour beetles (Tribolium castaneum and T. confusum) after infection with the bacterium Bacillus thuringiensis (Bt), identifying a role for the Toll pathway in generating heterogeneity in antibacterial resistance among species and populations. We then investigated the impact of eugregarine co-infection on these dynamics. Our results suggest that gregarines alter the local immunological landscape within the gut, but that the reduction in bacterial growth rates in gregarine co-infected individuals is driven primarily by competition for energetic resources among parasites. This study reveals a role for eukaryotic members of the microbiome in modulating disease susceptibility phenotypes in natural populations, and gives new insight into patterns of natural variation in immunological dynamics among host life stages, populations, and species.
