Nano-Mechanical Properties of Heat Inactivated Bacillus Anthracis and Bacillus Thuringiensis Spores

B. thuringiensis spores must have similar properties to B. anthracis spores to be a good simulant in counter-proliferation studies. In particular, they must behave in a similar way when exposed to high temperatures for short periods of time as would be caused by an explosion. This research project compares surface elasticities for four different spore sample types, B. anthracis spores, heat inactivated B. anthracis spores, B. thuringiensis spores, and heat inactivated B. thuringiensis spores. Heat inactivated spores were exposed to a temperature just high enough that no spores were observed to germinate. Elasticity values for the spore surfaces were determined by measuring the reflection and transmission of acoustic waves between a spore surface and an atomic force microscope (AFM) tip, assuming a Hertz contact model. B. thuringiensis spores had a higher and more variable elasticity then B. anthracis spores. Heat inactivation caused spore surface elasticity to decrease. Calculated average elasticities were 3.73 GPa for B. anthracis, 2.73 GPa for heat inactivated B. anthracis, 4.67 GPa for B. thuringiensis, and 3.57 GPa for heat inactivated B. thuringiensis