Abstract: Bifidocin A, a novel bacteriocin with antimicrobial activity against a wide range of foodborne bacteria produced by Bifidobacterium animalis BB04, has a potential application as biopreservative in the food industry. The objective of this study was to investigate the antibacterial mechanism of action of bifidocin A against Gram-negative strain based on the level of protein expression. The difference in the expression level of total cell proteins in Escherichia coli CGMCC1.90 before and after treatment with bifidocin A was analyzed by using two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Functional classification and enrichment analysis of differentially expressed proteins were carried out based on gene ontology annotation analysis. Results showed that a total of 12 differentially expressed protein spots were found after treatment with bifidocin A, two of which were upregulated and ten of which were downregulated. Ten differentially expressed proteins were identified by MALDI-TOF, which were mainly involved in cell membrane composition, energy metabolism and stress response. These results suggested that bifidocin A might inhibit the growth of E. coli by altering the cell membrane structure, blocking the tricarboxylic acid cycle, reducing the availability of energy and adenosine triphosphate (ATP) and decreasing the resistance of the cells to external stress conditions.

Key words: bacteriocin, Bifidobacterium spp., Escherichia coli, whole cell protein, expression