The skin microbiome facilitates adaptive tetrodotoxin production in poisonous newts
| Autor: | Lauren A. O’Connell, James A. Foster, Janet E Williams, Heather L. Eisthen, Patric M Vaelli, Kevin R. Theis |
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| Rok vydání: | 2020 |
| Předmět: |
Male
0301 basic medicine chemistry.chemical_compound Biology (General) Animals Poisonous Skin education.field_of_study biology Microbiota musculoskeletal neural and ocular physiology General Neuroscience General Medicine Adaptation Physiological Sphingopyxis embryonic structures Tetrodotoxin Medicine Chemical defense Research Article Symbiotic bacteria Amphibian animal structures QH301-705.5 Science Population Zoology Context (language use) TTX autoresistance General Biochemistry Genetics and Molecular Biology 03 medical and health sciences biology.animal Animals Symbiosis education Evolutionary Biology Bacteria 030102 biochemistry & molecular biology General Immunology and Microbiology urogenital system neurotoxin Salamandridae biology.organism_classification Culture Media body regions 030104 developmental biology chemistry Predatory Behavior ion channel Taricha taricha granulosa amphibian Other |
| Zdroj: | eLife eLife, Vol 9 (2020) |
| ISSN: | 2050-084X |
| DOI: | 10.7554/elife.53898 |
| Popis: | Rough-skinned newts (Taricha granulosa) use tetrodotoxin (TTX) to block voltage-gated sodium (Nav) channels as a chemical defense against predation. Interestingly, newts exhibit extreme population-level variation in toxicity attributed to a coevolutionary arms race with TTX-resistant predatory snakes, but the source of TTX in newts is unknown. Here, we investigated whether symbiotic bacteria isolated from toxic newts could produce TTX. We characterized the skin-associated microbiota from a toxic and non-toxic population of newts and established pure cultures of isolated bacterial symbionts from toxic newts. We then screened bacterial culture media for TTX using LC-MS/MS and identified TTX-producing bacterial strains from four genera, including Aeromonas, Pseudomonas, Shewanella, and Sphingopyxis. Additionally, we sequenced the Nav channel gene family in toxic newts and found that newts expressed Nav channels with modified TTX binding sites, conferring extreme physiological resistance to TTX. This study highlights the complex interactions among adaptive physiology, animal-bacterial symbiosis, and ecological context. eLife digest Rough-skinned newts produce tetrodotoxin or TTX, a deadly neurotoxin that is also present in some pufferfish, octopuses, crabs, starfish, flatworms, frogs, and toads. It remains a mystery why so many different creatures produce this toxin. One possibility is that TTX did not evolve in animals at all, but rather it is made by bacteria living on or in these creatures. In fact, scientists have already shown that TTX-producing bacteria supply pufferfish, octopus, and other animals with the toxin. However, it was not known where TTX in newts and other amphibians comes from. TTX kills animals by blocking specialized ion channels and shutting down the signaling between neurons, but rough-skinned newts appear insensitive to this blockage, making it likely that they have evolved defenses against the toxin. Some garter snakes that feed on these newts have also evolved to become immune to the effects of TTX. If bacteria are the source of TTX in the newts, the emergence of newt-eating snakes resistant to TTX must be putting evolutionary pressure on both the newts and the bacteria to boost their anti-snake defenses. Learning more about these complex relationships will help scientists better understand both evolution and the role of beneficial bacteria. Vaelli et al. have now shown that bacteria living on rough-skinned newts produce TTX. In the experiments, bacteria samples were collected from the skin of the newts and grown in the laboratory. Four different types of bacteria from the samples collected produced TTX. Next, Vaelli et al. looked at five genes that encode the channels normally affected by TTX in newts and found that all them have mutations that prevent them from being blocked by this deadly neurotoxin. This suggests that bacteria living on newts shape the evolution of genes critical to the animals’ own survival. Helpful bacteria living on and in animals have important effects on animals’ physiology, health, and disease. But understanding these complex interactions is challenging. Rough-skinned newts provide an excellent model system for studying the effects of helpful bacteria living on animals. Vaelli et al. show that a single chemical produced by bacteria can impact diverse aspects of animal biology including physiology, the evolution of their genes, and their interactions with other creatures in their environment. |
| Databáze: | OpenAIRE |
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