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. Inner membrane (IM) proteins (YetF, YdfS, and YkjA) were crucial for resistance to both OH and CH, with YetF being the most significant. 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 proteins and core molecules like DPA and the DNA-SASP complex.