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The Effects of Freeze-Thaw and UVC Radiation on Microbial Survivability in a Selected Mars-like Environment

Daniel Keaney1, Brigid Lucey1, Noreen Quinn2

  • 1Department of Biological Sciences, Munster Technological University, Bishopstown, T12 P928 Cork, Ireland.

Microorganisms
|March 26, 2022
PubMed

Insights

Certain microbes like Deinococcus radiodurans and Paraburkholderia fungorum show high survival rates under Mars-simulated freeze-thaw and UV conditions. Escherichia coli survival varies by strain, with some showing increased UV resistance after freezing.

Area of Science:

  • Astrobiology
  • Microbial Ecology
  • Planetary Science

Background:

  • Understanding microbial survival is crucial for assessing the potential for life on Mars and for planetary protection protocols.
  • Mars experiences extreme temperature fluctuations and significant UV radiation, posing challenges for extant or introduced life.

Purpose of the Study:

  • To evaluate the survivability of key bacterial species (Escherichia coli, Deinococcus radiodurans, Paraburkholderia fungorum) under simulated Martian environmental conditions.
  • To investigate the combined effects of freeze-thawing cycles and UV exposure on microbial viability.

Main Methods:

  • Microbial strains were subjected to repeated freeze-thaw cycles (-80 °C to +30 °C) and UV irradiation (254 nm) independently and in combination.
  • Viability assessments were performed after 20 freeze-thaw cycles and at various UV doses.
  • Comparative analysis of survival rates across different strains and conditions was conducted.

Main Results:

  • Deinococcus radiodurans (96% viability) and Paraburkholderia fungorum (72.6% viability) showed high survival after 20 freeze-thaw cycles.
  • Escherichia coli ATCC 25922 withstood high UV doses (870 J/m²), while Paraburkholderia fungorum and Deinococcus radiodurans exhibited remarkable UV resistance.
  • Freezing enhanced UV resistance in E. coli strains and D. radiodurans but increased UV susceptibility in P. fungorum.

Conclusions:

  • Deinococcus radiodurans and Paraburkholderia fungorum demonstrate significant resilience to Martian freeze-thaw and UV conditions.
  • Escherichia coli ATCC 25922 also shows potential for survival, with freezing paradoxically increasing its UV resistance.
  • These findings have implications for the search for life on Mars and the design of future astrobiological missions.
Keywords:
Deinococcus radioduransParaburkholderia fungorumUV resistanceastrobiologybacterial resistancetemperature cycling

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