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Heat Resistance Correlated with DNA Content in Bacillus megaterium Spores

B H Belliveau1, T C Beaman, P Gerhardt

  • 1Department of Microbiology and Public Health, Michigan State University, East Lansing, Michigan 48824-1101.

Applied and Environmental Microbiology
|September 1, 1990
PubMed

Insights

Heavier Bacillus megaterium spores exhibit greater heat resistance and DNA content, suggesting a link between spore genome copy number and thermotolerance. Mineral and dipicolinic acid levels did not differ between subpopulations.

Area of Science:

  • Microbiology
  • Bacterial Spore Research
  • Molecular Biology

Background:

  • Bacillus megaterium spores are known for their remarkable resistance.
  • Spore properties can vary, impacting their survival mechanisms.
  • Understanding factors influencing spore resistance is crucial for various applications.

Purpose of the Study:

  • To investigate the relationship between Bacillus megaterium spore density and thermoresistance.
  • To determine if DNA content correlates with heat resistance in Bacillus megaterium subpopulations.
  • To explore the underlying mechanisms of spore inactivation and heat resistance.

Main Methods:

  • Density gradient centrifugation to isolate Bacillus megaterium spore subpopulations.
  • Thermotolerance assays (e.g., D-value determination at 80°C).
  • Quantification of spore DNA content and analysis of mineral and dipicolinic acid composition.

Main Results:

  • Two distinct spore subpopulations with different densities (1.360 g/ml and 1.355 g/ml) were isolated.
  • The heavier spore subpopulation demonstrated significantly higher thermoresistance (D(80) = 186 min vs. 81 min).
  • Heavier spores contained higher DNA content (digenomic vs. monogenomic), while mineral and dipicolinic acid levels were comparable.

Conclusions:

  • Spore density is a reliable indicator of thermoresistance in Bacillus megaterium.
  • Higher DNA content, potentially indicating a digenomic state, is associated with increased heat resistance.
  • Mechanisms of heat resistance in Bacillus megaterium spores may be influenced by genome copy number, independent of mineral or dipicolinic acid content.

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