Pulsed Electric Field Treatments with Non-lethal Field Strength Alter the Properties of Bacterial Spores

Pulsed electric field (PEF) treatment, an alternative to thermal processing in the food industry, is difficult in inactivating bacterial spores. While spores that have been treated in this manner remain alive, specific understanding of their physiological properties is quite restricted. The purpose of this study is to describe the morphology, viability, and germination behavior of Bacillus atrophaeus ( B. atro ) spores treated with PEF. Our findings indicate that non-lethal PEF results in spore deformation, dipicolinic acid (DPA) leakage, and a shorter and more uniform germination lag time ( T lag ), but there is no change in release duration (Δ T release ), germination ratio, or viability. It implies that 1) an intact morphologic state and DPA content are not prerequisite for germination and full viability; and 2) in contrast to nutrient-induced germination where initially slowly released DPA triggers subsequent germination events, leaked DPA during PEF treatment does not. Spores that have been subjected to this procedure remain dormant and preserve their full germinablity; and 3) PEF-treated spores respond to germinants quicker and with less heterogeneity, possibly because the tiny cracks formed on the spore surface facilitate the germinants' access to the germination receptors situated on the spore's inner membrane. The consensus view that non-lethal PEF has less impact on spores which are still capable of forming CFU under proper condition is only one-sided. This research advances our understanding of how spores behave following non-lethal PEF treatment and gives information on the topics of nosocomial sterilization, food safety, and public health.