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| Deinococcus radiodurans |
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Show notes:
Microbe of the episode: Paramecium bursaria Chlorella virus CA4A
News item
Journal Paper:
Shuryak I, Matrosova VY, Gaidamakova EK, Tkavc R, Grichenko O, Klimenkova P, Volpe RP, Daly MJ. 2017. Microbial cells can cooperate to resist high-level chronic ionizing radiation. PLOS ONE 12:e0189261.
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Episode outline:
- Background: Radiation, in form of X-rays, can be dangerous
- Acute harm from large dose in short term, overcoming repair abilities
- But also chronic harm when exposed less over longer term
- Lower, extended doses relevant to certain things
- medicine, nuclear power, Space travel
- Harder to study effects cos dangerous, expensive
- So try looking at bacteria living around radioactive waste sites
- Some very resistant species, like Deinococcus radiodurans
- But also some less resistant, like Pseudomonas
- How do they survive?
- Deal with radiation by direct repair and also preventing damage
- Often caused by reactive oxygen species, prevented with antioxidants
- What’s new: Now, scientists publishing in PLOS One have discovered that sometimes more radiation-resistant microbes can protect other species from radiation damage!
- Methods: Exposed some bacteria and fungi to high or low radiation
- Escherichia coli, Deinococcus radiodurans
- Candida, Saccharomyces, Pichia etc yeasts
- Measured growth rates
- Most resistant to chronic were Deinococcus, then strain of E. coli, then yeast Trichosporon
- E. coli strain was selected by exposing to radiation and propagating cells that survived
- ~3x more resistant than parent strain
- Most resistant could grow under 126 Gy/h
- Almost half of dose next to Chernobyl reactor after meltdown
- Oxygen affected resistance a lot
- Prob more ROS
- ROS control important in general; enzymes that detoxify, cell numbers to handle it
- Measured ROS absorbance abilities; Deinococcus was best at that too
- Could help other cells in coculture?
- Deinococcus grown together with susceptible E. coli under 36 Gy/h
- E. coli couldn’t grow on its own, but together it grew slowly
- Summary: Under chronic low-level radiation, super-resistant bacterial species can protect less resistant cells from some of the harmful effects
- Applications and implications: Important to understand effects of chronic radiation exposure
- Good system for studying
- Also potential for cleaning up radioactive pollution sites with microbial bioremediation
- Before, reliance mostly on Deinococcus and other resistant organisms
- But now may be possible to use other, better organisms and have Deinococcus protect
- Also found other resistant organisms in this study that could be useful themselves
- Maybe apply antioxidant effects or bacteria themselves to others undergoing radiation
- Medical, astronauts, nuclear, etc
- What do I think: Evidence of difference between resistance to acute vs. chronic
- Deal with acute: amount of damage capacity is important, happens all at once
- With chronic: rate of repair instead, deal with it as it comes
- For acute, could shut down growth to fix things, but would be fatal under chronic
- So, worth it to make effort to study effects and tolerances of chronic radiation
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