Purification, characterization and mechanism of action of enterocin HDX-2, a novel class IIa bacteriocin produced by Enterococcus faecium HDX-2

A novel bacteriocin was isolated and purified by salt precipitation, C8 cartridge extraction, cation exchange and RP-HPLC. SDS-PAGE and MALDI-TOF-MS analysis showed that the Ms of enterocin HDX-2 5482 Da. The enterocin HDX-2 was sensitive to protease degradation; was stable in large pH range (pH 2-10); was heat stable (121 degrees C, 20 min); was stable in organic solvents, surfactants, and detergents; metal ion balance and bactericidal activity toward foodborne spoilage-associated and pathogenic bacteria. This novel enterocin HDX-2 was clas-sified as a class IIa bacteriocin. FT-IR and CD spectroscopy indicated an excessive proportion of alpha-helix structures. The MIC of enterocin HDX-2 against Listeria monocytogenes CMCC 1959 was 5.07 +/- 0.14 mu g/mL, and the MBC was 16.58 +/- 1.23 mu g/mL. Growth curves and time-kill kinetics showed that enterocin HDX-2 possessed a bactericidal action mode with concomitant cell lysis against pathogens. SEM and TEM analyses showed that enterocin HDX-2 prompted modifications in the morphology and, to a larger extent, in the intracellular activities of L. monocytogenes CMCC 1959 cells. Treatment of L. monocytogenes CMCC 1959 cells with enterocin HDX-2 resulted in the leakage of K+ and inorganic phosphate, the generation of ATP and UV-absorbing materials, and decreases in Delta psi and Delta pH.

Automated summary

The novel bacteriocin enterocin HDX-2 exhibited high stability and strong bactericidal activity against a variety of bacteria, with mechanisms such as cell lysis, alterations in cell morphology and intracellular activities, and induction of K+ and inorganic phosphate leakage in bacteria.