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Summary High temperatures (e.g., fever) and gut microbiota can both influence host resistance to infection. However, effects of temperature‐driven changes in gut microbiota on resistance to parasites remain unexplored. We examined the temperature dependence of infection and gut bacterial communities in bumble bees infected with the trypanosomatid parasiteCrithidia bombi. Infection intensity decreased by over 80% between 21 and 37°C. Temperatures of peak infection were lower than predicted based on parasite growthin vitro, consistent with mismatches in thermal performance curves of hosts, parasites and gut symbionts. Gut bacterial community size and composition exhibited slight but significant, non‐linear, and taxon‐specific responses to temperature. Abundance of total gut bacteria and of Orbaceae, both negatively correlated with infection in previous studies, were positively correlated with infection here. Prevalence of the bee pathogen‐containing family Enterobacteriaceae declined with temperature, suggesting that high temperature may confer protection against diverse gut pathogens. Our results indicate that resistance to infection reflects not only the temperature dependence of host and parasite performance, but also temperature‐dependent activity of gut bacteria. The thermal ecology of gut parasite‐symbiont interactions may be broadly relevant to infectious disease, both in ectothermic organisms that inhabit changing climates, and in endotherms that exhibit fever‐based immunity.
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This content will become publicly available on December 1, 2026
Gut bacteria induce heterologous immune priming in Rhodnius prolixus encompassing both humoral and cellular immune responses
Insects lack the adaptive, antibody mediated responses of vertebrates, yet they possess a robust innate immune system capable of defending themselves against pathogens. Immune priming has been observed in multiple insect species, wherein exposure to a pathogen provides protection against subsequent infections by the pathogen. Heterologous immune priming has also been described, where presence of one bacterial species provides protection against another. We determined thatRhodococcus rhodnii, a gut symbiont of the kissing bugRhodnius prolixus,induces strong heterologous immune priming, while axenic bugs lacking gut bacteria are highly susceptible to pathogens. CommensalEscherichia coliprovides less robust protection.R. rhodniimust be alive within the insect as dead bacteria do not stimulate immune priming and pathogen resistance. Removal ofR. rhodniifrom the gut reduces resistance to pathogens while restoring it to axenic bugs improves pathogen resistance, though not completely. Unlike most other examples of symbiont-mediated immune priming, we find no evidence thatR. rhodniiever leaves the gut, despite activating a potent immune response in the hemocoel and fat body.R. rhodniiandE. coliactivate both the IMD and Toll pathways indicating cross-activation of the pathways, while silencing of either pathway leads to a loss of the protective effect. Several antimicrobial peptides are induced in the fat body by presence of gut bacteria. WhenE. coliis in the gut, expression of antimicrobial peptides is often higher than whenR. rhodniiis present, whileR. rhodniiinduces proliferation of hemocytes and induces a stronger melanization response thanE. coli. Hemolymph fromR. rhodniibugs has a greater ability to convert the melanin precursor DOPA to melanization products than axenic orE. coli-harboring bugs. These results demonstrate thatR. rhodnii’sbenefits to its host extend beyond nutritional provisioning, playing an important role in the host immune system.
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- Award ID(s):
- 2239595
- PAR ID:
- 10660069
- Editor(s):
- Vale, Pedro F
- Publisher / Repository:
- Public Library of Science
- Date Published:
- Journal Name:
- PLOS Pathogens
- Volume:
- 21
- Issue:
- 12
- ISSN:
- 1553-7374
- Page Range / eLocation ID:
- e1012947
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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