[BIOLOGICAL ACTIVITY OF ANTIMICROBIAL PEPTIDES OF ENTEROCOCCUS FAECIUM]

Isolate bacteriocins from Enterococcus faecium metabolites and characterize their effect on cells of Gram positive (Listeria monocytogenes) and Gram negative (Escherichia coli) bacteria.

Methods of solid-phase extraction, ion-exchange and reversed phase chromatography were applied for isolation of bacteriocins from cultural medium of bacteria MALDI time-of-flight mass-spectrometry was used for characterization of the obtained preparations. The mechanism of biological effect of peptides was evaluated using DNA-tropic dyes (SYTO 9 and PI) with subsequent registration of fluorescence spectra: Atomic-force microscopy (AFM) was used for characterization of morpho-functional reaction of target cells.

Peptide fractions with mass of 1.0 - 3.0 kDa were isolated from enterococci metabolites, that inhibit the growth of indicator microorganisms. E. faecium strain exoproducts were shown to increase membrane permeability during interaction with L. monocytogenes, that results in subsequent detectable disturbance of normal cell morphology of listeria. Alterations of E. coli surface during the effect of purified peptide fraction was detected using AFM.

The studies carried out have revealed the effect of bacteriocins of enterococci on microorganisms with various types of cell wall composition and have confirmed the importance of bacterial barrier structure permeability disturbance in the mechanism of antimicrobial effect of enterocins.