Studies on antibacterial activity and mechanism of Enterococcus faecium ID4 bacteriocin
Enterococcus faecium ID4(CGMCC28567)is a novel bacteriocin-producing strain isolated from the oral cavity of a healthy volunteer.The bacteriocin produced by E.faecium ID4 was partially purified by ammonium sulfate precipitation and subsequently by Seph-adex G-25 column chromatography.The molecular mass of ID4 bacteriocin was determined by Tricine-SDS-PAGE electrophoresis and bio-autography.Results showed that the molecular mass of ID4 bacteriocin was about 6.5 kDa.The ID4 bacteriocin possessed high thermal sta-bility and the antibacterial activity remained unchanged at 121℃ for 15 min.The antibacterial activity remained stable at pH 2～6,while decreased significantly after treatment with various proteases.The bacteriocin was shown a narrow antibacterial spectrum and a significant bactericidal effect on Nocardia coeliaca BD 7184 and streptococci such as Streptococcus mitis.The bactericidal effect of ID4 bacteriocin was via perforation on the indicator cell membrane,resulting in the leakage of the intracellular matrix.ID4 bacteriocin showed no hemolytic ac-tivity and no cytotoxicity to Caco-2 cells.Consequently,bacteriocins produced by E.faecium ID4 have the potential to treat oral bacterial infections.
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