Insight into the antibacterial activity and membrane-damage mechanism of pyrrole-2-carboxylic acid against Listeria monocytogenes

Natural antimicrobials have potential to suppress the growth of foodborne pathogens. In this work, the antibacterial property and membrane-disruptive mechanism of pyrrole-2-carboxylic acid (PCA), against Listeria monocytogenes were elucidated. Leakage of cell constituents (K+ and nucleotide) and flow cytometric analysis indicated that PCA caused a significant change in the permeability and integrity of cell membrane of L. monocytogenes. Meanwhile, remarkable morphological alterations and membrane hyperpolarization of L. monocytogenes validated the disruptive ability of PCA on cell membrane. Additionally, PCA could interact with membrane protein, and cause changes in the conformation of protein. Untargeted lipidomics revealed that PCA triggered alternations in the composition and architecture of the membrane lipids mainly involved in glycerophospholipid and glycerolipid metabolism, thus leading to cell membrane dysfunction. Furthermore, PCA at concentration of 0.75 mg/mL could inhibit the contamination of L. monocytogenes in lettuce stem and beef, with a decrease of 2.4 log CFU/cm2 (P ＜ 0.05) for lettuce stem and 1.8 log CFU/cm2 (P ＜ 0.05) for beef after 10 days of storage. This work illuminates the key targets of PCA against the cell membrane of L. monocytogenes, facilitating the application of natural organic acids as candidate food preservatives in the food industry.