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| Caenorhabditis elegans By Bob Goldstein, UNC Chapel Hill Own work, CC BY-SA 3.0 |
Download Episode (7.5 MB, 8.1 minutes)
Show notes:
Microbe of the episode: Siegesbeckia yellow vein betasatellite
News item
Journal Paper:
Rafaluk‐Mohr C, Ashby B, Dahan DA, King KC. 2018. Mutual fitness benefits arise during coevolution in a nematode-defensive microbe model. Evol Lett 2:246–256.
Other interesting stories:
- Phages can hide in bacterial spores and attack when the bacteria revive (paper)
- Probiotics seemed to increase risk in mice from gut parasite
- Studying the value of using probiotics before or after antibiotics
- More microbes than realized, even in gut, may be able to generate electricity
- Magnetotactic bacteria are really cool
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Episode outline:
- Background: Microbes everywhere in and around bodies
- Despite tiny size, lots of them
- Can have major effects on hosts, good or bad
- Many beneficial microbes form long-term relationships with hosts
- Evolve together, dependent on each other
- But how do these relationships start?
- What’s new: Now, scientists publishing in Evolution Letters have discovered that a bacterium in roundworms is mildly harmful by itself but helpful in protecting the worms from worse pathogens!
- Worms are Caenorhabditis elegans, common model lab organism
- Every cell in body is well understood
- Enterococcus faecalis prevents worms from thriving as much when alone
- But not as virulent/harmful as bacterium Staphylococcus aureus
- Methods: Let worms and bacteria evolve together over generations
- Either alone or under threat from Staphylococcus
- Relationship of protection developed strongly under threat, 5% more host survival
- Took 14 generations for relationship to develop
- Worms evolved along with Enterococcus bacteria did better than ancestral worm strain
- Similar with worms evolved with bacteria in absence of Staphylococcus threat
- Made mathematical model of system to make predictions
- Prediction: mutualism most likely to evolve when helpful bacteria are moderately helpful
- If not very helpful, only costly, host shuts them out
- If too helpful, pathogen is not a threat and goes away, so then helpful are only harmful
- But if helpful is just helpful enough, host keeps them around for continuing protection
- Summary: Worms and microbes that evolved together benefit each other more than worms not evolved to work with the microbes or microbes not evolved to work with the worms
- Applications and implications: Relevant to health – our microbe relationships
- Also microbes + parasites, fungal pathogens, etc
- Agriculture and such – plant microbes, animal microbes
- And herbivore pests/animal pests and their microbes
- What do I think: Mutual relationships with microbes not new concept
- But not often caught in the moment of happening
- Only 14 generations to evolve relationship
- Not that long, considering evolutionary time scales
- Short enough to document in research paper
- Interesting to study what specifically changed in each
- Probably in worm, less defenses against microbe
- What about microbe?
- Changing environment can cause relationships to develop in new ways
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