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Novel strains of Moorella thermoacetica form unusually heat-resistant spores

D E Byrer1, F A Rainey, J Wiegel

  • 1Department of Microbiology and Center for Biological Resource Recovery, University of Georgia, USA.

Archives of Microbiology
|January 11, 2000
PubMed

Insights

Two Moorella thermoacetica strains form exceptionally heat-resistant spores, requiring extensive heat activation for germination. These spores exhibit remarkable thermal resistance, with decimal reduction times at 121°C indicating significant survival capabilities.

Area of Science:

  • Microbiology
  • Bacterial spore resistance
  • Extremophile research

Background:

  • Moorella thermoacetica is an anaerobic bacterium.
  • Bacterial spores are known for their resistance to harsh environmental conditions, including heat.
  • Understanding spore resistance mechanisms is crucial for sterilization processes and microbial ecology.

Purpose of the Study:

  • To investigate the unusually heat-resistant spores formed by two strains of Moorella thermoacetica (JW/B-2 and JW/DB-4).
  • To characterize the heat activation requirements and thermal resistance of these spores.
  • To correlate spore structure with observed heat resistance.

Main Methods:

  • Isolation and cultivation of Moorella thermoacetica strains under different growth conditions (chemolithoautotrophic and chemoorganoheterotrophic).
  • Determination of heat activation requirements for spore germination.
  • Kinetic analysis of spore germination and determination of decimal reduction times (D10-times) at 121°C.
  • Electron microscopy to analyze spore structure, including cortex thickness and exosporia.

Main Results:

  • Spores required prolonged heat activation (>2 min at 100°C, up to 90 min for maximal germination).
  • Kinetic analysis revealed two distinct subpopulations of heat-resistant spores.
  • Decimal reduction times (D10) at 121°C varied significantly based on growth and spore maturation conditions, with some exceeding 100 minutes.
  • Electron microscopy showed variations in cortex thickness and revealed structures in the exosporia.

Conclusions:

  • The studied Moorella thermoacetica strains produce some of the most heat-resistant bacterial spores documented.
  • Spore resistance is influenced by growth conditions and maturation temperature.
  • Structural components, particularly within the exosporia, may contribute to the extreme heat resistance observed.

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