Location: Bee Research Laboratory
Project Number: 8042-21000-291-061-I
Project Type: Interagency Reimbursable Agreement
Start Date: Aug 1, 2022
End Date: Jul 31, 2024
This project will focus on the emergent honey bee parasite Lotmaria passim and its control by honey bee gut symbionts. Objective 1 is to compare temperature dependence of growth in this parasite vs. symbiont cell cultures. increase with temperature. Objective 2 will be to test whether parasite growth is inhibited by symbionts, and how this inhibitory activity is related to pH and affected by temperature. Objective 3 will be to determine the effects of temperature, microbiota, and their interaction on infection and gut chemistry of live bees. These experiments will test predictions from cell culture experiments in infected honey bees.
Objective 1 involves establishing cell cultures of the parasite L. passim and major gut symbionts across the range of temperatures found in bee colonies. Data will be used to quantify differences in optimum and maximum temperatures between parasites and symbionts, and changes in their relative growth rates over the colony temperature range. Objective 2 will use the cell cultures of Obj. 1 to test for pH-mediated, temperature-dependent interactions between symbionts and parasites. The first approach will be to quantify the pH range necessary to inhibit parasite growth by acidifying L. passim culture medium with symbiont “spent medium” (i.e., medium in which symbionts have been grown) and constituent acidic metabolites. The pH necessary to inhibit parasite growth will be compared with that measured in bee intestines to predict whether gut acidity could substantially reduce infection in bees. Next, the temperature dependence of symbiont-mediated inhibition will be determined by growing parasites and symbionts in mixed-species ‘co-culture’. These experiments will indicate how temperature affects the antiparasitic action of symbionts, and how the presence of symbionts affects the thermal niche and heat tolerance of parasites. To accomplish objective 3, interactive effects of temperature and gut microbiota on resistance to parasites will be measured by comparing infection intensity across a range of temperatures in symbiont-colonized vs. germ-free bees. This objective will use metabolomics and RNA sequencing to identify (a) potential parasite growth-limiting metabolites, (b) temperature-mediated changes in host immune gene expression, and (c) heat shock-induced genes of parasites that are essential for successful infection at high temperature.