Electro-Mechanical Stresses on Bacillus Atrophaeus Bacterial Spore Germination Induced by Pulsed Electric Fields

In this work, the electro-mechanical stresses induced by pulsed electric fields (PEF) on bacterial spore germination was modeled and empirically tested using Bacillus atrophaeus spores. Specifically, a new model, termed as Qiu-Wu’s electro-mechanical (QW’s EM) spore model, was derived to analyze the effect of electro-mechanical stresses on spores subjected under electric fields. A non-linear inverse relationship was found between electric fields and thickness change of spore coat. SEM, pH, hydrophobicity and electrochemical measurements were implemented for verification of the model. PEF-treated spores germinated with a faster rate and a higher degree of homogeneity. The longer the treatment time, the better the homogeneity. The speed of dipicolinic acid (DPA) release was around 20% faster in PEF-treated samples, while the peak intensity of terbium-DPA from PEF-treated samples was up to 80% lower. Theoretical analysis and empirical results were consistent to show that PEF introduces electro-mechanical stresses to expedite spore germination. The significance and impact of this study is obvious: bacterial spore is implicated in food spoilage and foodborne diseases primarily via the process of germination, and PEF technology has been introduced to inactivate microorganisms in food. Understanding the mechanism of germination under PEF can provide deep understanding for inactivation of foodborne pathogens and better food preservation methods.