Sunday, June 17, 2018

BacterioFiles 343 - Super Cells Save Susceptible Species

Deinococcus radiodurans
This episode: Very radiation-resistant bacteria can protect other, less-resistant microbes from some of the effects of chronic radiation!

Download Episode (9.7 MB, 10.6 minutes)

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.

Other interesting stories:
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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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