Characterization and Application of Enterocin RM6, a Bacteriocin fromEnterococcus faecalis

Abstract

Use of bacteriocins in food preservation has received great attention in recent years. The goal of this study is to characterize enterocin RM6 from Enterococcus faecalis OSY-RM6 and investigate its efficacy against Listeria monocytogenes in cottage cheese. Enterocin RM6 was purified from E. faecalis culture supernatant using ion exchange column, multiple C18-silica cartridges, followed by reverse-phase high-performance liquid chromatography. The molecular weight of enterocin RM6 is 7145.0823 as determined by mass spectrometry (MS). Tandem mass spectrometry (MS/MS) analysis revealed that enterocin RM6 is a 70-residue cyclic peptide with a head-to-tail linkage between methionine and tryptophan residues. The peptide sequence of enterocin RM6 was further confirmed by sequencing the structural gene of the peptide. Enterocin RM6 is active against Gram-positive bacteria, including L. monocytogenes, Bacillus cereus, and methicillin-resistant Staphylococcus aureus (MRSA). Enterocin RM6 (final concentration in cottage cheese, 80 AU/mL) caused a 4-log reduction in population of L. monocytogenes inoculated in cottage cheese within 30 min of treatment. Therefore, enterocin RM6 has potential applications as a potent antimicrobial peptide against foodborne pathogens in food.

Circular Bacteriocins: Biosynthesis and Mode of Action

“…Subgroup i includes the most highly characterized circular bacteriocin, enterocin AS-48, as well as carnocyclin A (9), circularin A (10), uberolysin (11), lactocyclicin Q (12), leucocyclicin (13), garvicin ML (14), and amylocyclin (15) (Table 1). A circular bacteriocin recently identified from Enterococcus faecalis, named enterocin RM6, was shown to be identical to enterocin AS-48 (16). The subgroup i peptides are characterized by having several positively charged amino acid residues (overall cationic charge) and high isoelectric points (pIs of ϳ10) ( Table 1).…”

Inhibition of Bacillus cereus Strains by Antimicrobial Metabolites from Lactobacillus johnsonii CRL1647 and Enterococcus faecium SM21

“…These features are identical to other Enterococcus spp. strains, which have been studied mainly due to their bacteriocin synthesis [16,21,44,45]. In this case, the CFS from E. faecium SM21 showed an important inhibition against B. cereus vegetative cells tested both at pH 5.0 (final fermentation pH) and at pH 6.5, which confirms that inhibition of B. cereus is due not only to organic acids but to also enterocins.…”

“…On the other hand, bacteriocins are ribosomally synthesized peptides or proteins that have a bactericidal or bacteriostatic effect on other bacteria [13]. Many bacteriocins have shown antimicrobial activity against endosporeforming bacterial cells and in vitro spore germination [14][15][16][17][18]. However, in the particular case of B. cereus inhibition by bacteriocins or bacteriocin-like compounds in food systems, the scientific references are scarce [19][20][21][22].…”

Modified microassay for the isolation of antimicrobial-producing, spore-forming and nonspore-forming bacteria

“…; Huang et al . ) as follows. Isolates were grown in MRS broth at 30°C for ~24 h. Five hundred microlitres of culture were centrifuged at 16 000 g for 1 min.…”

“…; Huang et al . ) and the Taq DNA polymerase kit (Qiagen). Thermocycling conditions were as follows: (i) 94°C for 3 min, (ii) 35 cycles of 94°C for 1 min, 52°C for 1 min and 72°C for 2 min, and (iii) 72°C for 10 min.…”