The high-resolution architecture and structural dynamics of Bacillus spores

Area of Science:

• Microbiology
• Biophysics
• Materials Science

Background:

• Imaging microbial cell surfaces at the nanoscale under native conditions is crucial for understanding pathogenesis, immunobiology, environmental resistance, and biotransformation.
• Previous studies lacked high-resolution native structural data of bacterial endospores.

Purpose of the Study:

• To visualize the high-resolution native structures of bacterial endospores using in vitro atomic force microscopy.
• To investigate the self-assembly mechanisms of spore coats and the dynamic physical nature of dormant spores.
• To determine the interspecies distributions of spore dimensions in different environmental conditions.

Main Methods:

• In vitro atomic force microscopy (AFM) was employed to image bacterial endospores.
• Four species of Bacillus endospores were analyzed in both air and water environments.
• Measurements of spore dimensions (length and width) were taken under varying hydration states.

Main Results:

• High-resolution native structures of bacterial endospores, including the exosporium and spore coats, were visualized for four Bacillus species.
• Spore coat self-assembly mechanisms were found to be similar to inorganic and macromolecular crystallization.
• Bacillus atrophaeus spores showed a reversible 12% decrease in dimensions when transitioning from hydrated to air-dried states, indicating dynamic behavior.
• Significant differences in spore dimensions were observed across species, growth conditions, and environments.

Conclusions:

• Bacterial endospores are dynamic structures that change dimensions with environmental conditions.
• The self-assembly of spore coats follows principles similar to crystallization processes.
• Understanding spore structural variability is important for reconstructing spore formation conditions and modeling spore dispersal.