Diversity of enterococcal bacteriocins and their grouping in a new classification scheme

Abstract

Enterococci are lactic acid bacteria of importance in food, public health and medical microbiology. Many strains produce bacteriocins, some of which have been well characterized. This review describes the structural and genetic characteristics of enterocins, the bacteriocins produced by enterococci. Some of these can be grouped with typical bacteriocins produced by lactic acid bacteria according to traditional classification, whereas others are atypical and structurally distinct from the general classes of bacteriocins. These atypical enterocins recently played an important role in and prompted reclassification of the class II bacteriocins into a new scheme. In this review, a more simplified classification scheme for enterocins based on amino acid sequence homologies is proposed. Enterocins are of interest for their diversity and potential for use as food biopreservatives. The emergence of multiple antibiotic-resistant enterococci among agents of nosocomial disease and the presence of virulence factors among food isolates requires a careful safety evaluation of isolates intended for potential biotechnical use. Nevertheless, enterococcal bacteriocins produced by heterologous hosts or added as cell-free preparations may still be attractive for application in food preservation.

Cloning and Genetic Analyses of the Bacteriocin 41 Determinant Encoded on the Enterococcus faecalis Pheromone-Responsive Conjugative Plasmid pYI14: a Novel Bacteriocin Complemented by Two Extracellular Components (Lysin and Activator)

“…The mature EnlA protein consists of 316 amino acids and is homologous to the catalytic domains of a variety of cell walldegrading proteins. It might be that bacteriocin 41 belongs to the same group of enterococcal cell wall-degrading bacteriocins as EnlA, although the details of the mechanism of expression of EnlA, including the immunity factor, have not been clearly elucidated (15). However, our results imply that the mechanism of bacteriocin 41 expression is more complex than the EnlA expression system and that they are divergent systems.…”

“…E. faecalis FA-2-2 and OG1-10 and E. hirae have been chosen as representative enterococcal strains for the examination and classification of the bacteriocins produced by the clinical isolates in this study. Class 1 types produce the ␤-hemolysin/ bacteriocin (cytolysin) and are active against a wide variety of gram-positive bacteria, including S. aureus (2,15,17,24,46). The ␤-hemolysin/bacteriocin (cytolysin) of pAD1 belongs to class 1.…”

“…Several E. faecalis bacteriocins have been genetically and biochemically characterized (15,35), including the ␤-hemolysin/bacteriocin (cytolysin) (6,7,18,20,22) and the peptide antibiotics AS-48 (33), bacteriocin 21 (47), and bacteriocin 31 (46), which are encoded by the E. faecalis conjugative plasmids pAD1 (58 kbp), pMB2 (58 kbp), pPD1 (59 kbp), and pYI17 (57.5 kbp), respectively. A significant number of E. faecalis clinical isolates produce hemolysin/bacteriocin (10,26), and more than 50% of the hemolytic clinical isolates carry transferable hemolysin/bacteriocin determinants (21,26).…”

Phenotypic and Genotypic Characterization of Bacteriocins in Enterococcal Isolates of Different Sources

“…The similar results were reported in previous studies that most enterocin producing enterococci displayed antilisterial activity, while a fewer portion of them also showed antibacterial spectrum activity against Staphylococcus spp., Bacillus spp. and Clostridium spp [3,10,[16][17][18]. No correlation was found between the origin of the strains and the inhibitory spectrum.…”

“…It is assumed that bacteriocin production is a bacterial defense mechanism, which gives the producer strain a competitive advantage towards non-producer and bacteriocin sensitive strains in the same niche. In recent years, Franz et al, proposed simplified classification scheme for enterocins; Class I enterocins (lantibiotic enterocins), Class II enterocins (small, non-lantibiotic peptides); Class III enterocins (cyclic enterocins); and Class IV enterocins (large proteins) [3]. Cytolysin belongs to Class I enterocins, it is a two-peptide bacteriocin and both structural subunits contain lanthionie residues [4].…”