Location: Bee Research Laboratory
Project Number: 8042-21000-291-041-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Jun 1, 2021
End Date: Sep 30, 2023
This project will focus on controlling parasite infections by regulating temperature and gut symbionts in ways that inhibit an emerging parasite. Objective 1 will use metabolic theory equations to compare temperature dependence of growth in parasite and symbiont cell cultures. Objective 2 will test whether parasite growth is inhibited by symbionts, and how this inhibitory activity is related to pH and affected by temperature. Using the same cell cultures as in Obj. 1, pH-mediated, temperature-dependent interactions between symbionts and parasites will be explored. Objective 3 will 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.
To carry out Objective 1 (Use metabolic theory equations to compare temperature dependence of growth in parasite and symbiont cell cultures), ARS will grow cell cultures of the parasite L. passim and core gut symbionts S. alvi, G. apicola, and Lactobacillus Firm-5 across a range of temperatures that span the values recorded in A. mellifera workers (20-40 °C). Three strains of each species will be used to capture potential intraspecific differences in thermal performance curves. Cells will be seeded at an initial optical density (OD) of 0.05 and measured by OD every 12 h (L. passim) or 3 h (bacteria). Temperature treatments will be administered in parallel using six microbiological incubators. Experiments will be repeated three times, with temperatures of incubators reassigned between each repetition to avoid confounding the effects of incubator and temperature. For each strain, species, and temperature, growth rate will be estimated as the maximum slope of the curve of ln (OD) vs. time. To test whether parasite growth is inhibited by symbionts, and how this inhibition is related to pH and affected by temperature (Objective 2), experiments will test for parasite-inhibitory effects of spent medium and acidity (pH), temperature dependence of acid production by symbionts, and temperature dependence of symbionts’ effects on parasite cell cultures. Obj. 3: Determine effects of temperature, microbiota, and their interaction on infection and gut chemistry of live bees will require two sets of experiments. The first will test the effects of temperature, gut microbiota, and their interaction on infection intensity and gut microbial community structure. The second will test the effects of temperature on gut chemistry, with specific attention to gut pH and concentrations of acids hypothesized to inhibit parasite growth.