Pathways for accelerated bacterial spore killing with ohmic heating.

Area of Science:

• Food science and technology
• Microbiology
• Biophysics

Background:

• Conventional heating (CH) is standard for bacterial spore inactivation.
• The mechanism of accelerated spore killing by ohmic heating (OH) remains unclear.
• Understanding OH's effects on bacterial spores is crucial for food safety.

Purpose of the Study:

• To elucidate the mechanism by which ohmic heating (OH) enhances bacterial spore killing.
• To investigate the impact of OH on specific components within Bacillus subtilis spores.
• To identify key molecular targets responsible for OH-induced spore inactivation.

Main Methods:

• Utilized genetically modified Bacillus subtilis spores.
• Employed flow cytometry to assess membrane integrity.
• Conducted molecular dynamics (MD) simulations to examine DNA-SASP complex behavior under electric fields.

Main Results:

• YetF protein demonstrated the highest resistance to both OH and CH, contributing significantly to spore resistance.
• SASP, SpoVA proteins, and Ca-DPA showed interactions with the electric field.
• Increased propidium iodide staining indicated significant inner membrane damage with higher field intensities.
• MD simulations revealed electric field-induced dissociation of the SASP-DNA complex, increasing with field intensity.

Conclusions:

• Ohmic heating accelerates bacterial spore killing by impacting key inner membrane proteins and core molecules.
• The electric field in OH disrupts the SASP-DNA complex, contributing to spore inactivation.
• YetF protein plays a critical role in spore resistance to both OH and CH.