Inactivation and morphological damage of Vibrio parahaemolyticus treated with high hydrostatic pressure

The effects of high hydrostatic pressure (HHP) treatments on Vibrio parahaemolyticus cells were investigated using viability counting, scanning and transmission electron microscopy, and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) in order to determine optimal inactivation conditions and further understand the mechanisms of microorganism inactivation under HHP. The results showed that 300-MPa treatment for 10 min could extensively inactivate V. parahaemolyticus, with the number of viable bacteria decreasing from 109 CFU/mL to no viable bacteria. Damage to the cell wall, cell membrane, and cytoplasmic components by HHP treatments can be observed on scanning as well as transmission electron microscopy images. SDS-PAGE results showed that the protein bands differed between HHP untreated and treated V. parahaemolyticus, whereas HHP decreased protein content and caused partial protein degradation. Therefore, our results indicate that HHP can be applied to inactivate V. parahaemolyticus by inducing morphological changes in internal and external structures in the cell, as well as by causing cell membrane damage, cell wall rupture, and membrane protein degradation.