Pathways for accelerated bacterial spore killing with ohmic heating.

The mechanism by which ohmic heating (OH) accelerates bacterial spore killing compared to conventional heating (CH) is unclear. This study used genetically modified Bacillus subtilis spores to investigate OH's impact on specific components. Flow cytometry assessed membrane integrity, and molecular dynamics (MD) simulations examined the DNA-SASP complex under an electric field. Among the inner membrane (IM) proteins (YetF, YdfS, and YkjA) tested for its resistance against OH and CH, YeTF was found to be the most significant contributor to spore resistance for both treatments. SASP, SpoVA proteins, and Ca-DPA interacted with the field, showing specific effects at certain temperature and field intensity combinations. Flow cytometry showed spore staining with propidium iodide (PI), which increased with higher field intensities, indicating significant IM damage. MD simulations showed that the electric field caused the SASP-DNA complex to dissociate, with greater separation at higher field intensities. Thus, OH accelerates spore killing by affecting key IM and core molecules.