High temperatures augment inhibition of parasites by a honey bee gut symbiont

Authors: PALMER-YOUNG, EVAN - Department Of Agriculture Government Of Sri Lanka; MARKOWITZ, LINDSEY - University Of Maryland; HUANG, W.F. - US Department Of Agriculture (USDA); Evans, Jay

Submitted to: Proceedings of the Royal Society of London B
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2023
Publication Date: 10/4/2023
Citation: Palmer-Young, E.C., Markowitz, L.M., Huang, W., Evans, J.D. 2023. High temperatures augment inhibition of parasites by a honey bee gut symbiont. Proceedings of the Royal Society of London B. 89(10). Article e01023-23. https://doi.org/10.1128/aem.01023-23.
DOI: https://doi.org/10.1128/aem.01023-23

Interpretive Summary: Honey bees carry both beneficial and harmful microbes. The gut parasite Lotmaria passim reduces honey bee survivorship and has been linked with colony losses. Lactic-acid bacteria in the guts of honey bees ca change the gut environment in ways that reduce disease. Here we show that simple changes in acidity can explain the effects of gut symbionts on this parasite, leading the way to probiotic or management schemes to reduce honey bee parasites.

Technical Abstract: Temperature affects growth, metabolism, and interspecific interactions in microbial communities. Within animal hosts, gut bacterial symbionts can provide resistance to parasitic infections. Infection can also be shaped by host body temperature. However, the effects of temperature on the antiparasitic activities of gut symbionts have seldom been explored. The Lactobacillus-rich gut microbiota of facultatively endothermic honey bees is subject to seasonal and ontogenetic changes in host temperature that could alter the effects of symbionts against parasites. We used cell cultures of a Lactobacillus symbiont and an important trypanosomatid gut parasite of honey bees to test the potential for temperature to shape parasite-symbiont interactions. We found that symbionts showed greater heat tolerance than parasites and chemically inhibited parasite growth via production of acids. Acceleration of symbiont growth and acid production at high temperatures resulted in progressively stronger antiparasitic effects across a temperature range typical of bee colonies. Consequently, the presence of symbionts reduced both peak growth rate and heat tolerance of parasites. Results suggest that the endothermic behavior of honey bees could potentiate the effectiveness of gut symbionts that limit parasites’ ability to withstand high temperature, implicating thermoregulation as a reinforcer of core symbioses and possibly microbiome-mediated antiparasitic defense.