Purification of a Novel Bacteriocin-Like Inhibitory Substance Produced by Enterococcus faecium ICIS 8 and Characterization of Its Mode of Action

Objective: The aim of this work was to purify and characterize a bacteriocin-like antimicrobial substance produced by an antagonistic active strain of Enterococcus faecium . Methods and Results: A novel bacteriocin-like inhibitory substance (BLIS) produced by the E. faecium ICIS 8 strain was purified and characterized using sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE), and N-terminal amino acid sequencing revealed the following partial sequence: NH 2 -APKEKCFPKYCV. The proteinaceous nature of purified BLIS was assessed by treatment with proteolytic enzyme. Studies of the action of BLIS using bacteriological and bioluminescence assays revealed a dose-dependent inhibition of Listeria monocytogenes 88BK and Escherichia coli K12 TG1 lac::lux viability. The interaction of the BLIS with the bacterial surface led to the compensation of a negative charge value, as shown by zeta-potential measurements. Assessments of membrane integrity using fluorescent probes and atomic force microscopy revealed the permeabilization of the cellular barrier structures in both L . monocytogenes and E. coli . Conclusion: The novel BLIS from E. faecium ICIS 8 was characterized by a unique primary peptide sequence and exerted bactericidal activity against L . monocytogenes and E. coli by disrupting membrane integrity.