Identification of Structural and Immunity Genes of a Class IIb Bacteriocin Encoded in the Enterocin A Operon of Enterococcus faecium Strain MXVK29

Abstract

The Enterococcus faecium strain MXVK29, isolated from fermented sausages, produces a bacteriocin with a molecular mass of 3.5 kDa that belongs to the class of enterocins II.1, according to the terminal amino acid sequence, and has been identified as enterocin A. This bacteriocin is active against selected strains of Listeria, Staphylococcus, Pediococcus, and Enterococcus. In this study, we identified the genes adjacent to the structural gene for this bacteriocin, such as the immunity gene (entI) and the inducer gene (entF). Accessory genes for this bacteriocin, such as entK, entR, and entT, were identified as well, in addition to the orf2 and orf3, showing a high identity with class IIb peptides bacteriocins. The orf2 shows the consensus motif GxxxG, similar to those shown by bacteriocins such as PlnNC8α, EntCα, and Ent1071A, whereas orf3 shows a consensus motif SxxxS similar to that present in PlnNC8β (AxxxA). PlnNC8 is expressed only in bacterial cocultures, so there is the possibility that the expression of this two-peptide bacteriocin can be induced by a similar mechanism. So far, only the expression of enterocin A has been found in this strain; however, the presence of the genes ent29α and ent29β opens the possibility for further research on its induction, functionality, and origin. Although there are reports on this type of bacteriocin (EntX, EntC, and Ent1071) in other strains of E. faecium, no report exists yet on an Enterococcus strain producing two different classes of bacteriocin.

Classification of the Gut Microbiota of Patients in Intensive Care Units During Development of Sepsis and Septic Shock

“…Additionally, Enterococcus , which can cause urinary tract infections, abdominal-pelvic infections, and endocarditis [21] , [22] , [23] , was dominant in ICU E2. Enterococcus has also been reported to enhance immunity and inhibit overgrowth of opportunistic pathogens by producing short-chain fatty acids [24] , [25] and bacteriocins [26] , [27] , [28] . Therefore, the enterococcal overgrowth in ICU E2 might be associated with a lower occurrence of septic shock in patients with ICU E2.…”

Heterologous Biosynthesis of Five New Class II Bacteriocins From Lactobacillus paracasei CNCM I-5369 With Antagonistic Activity Against Pathogenic Escherichia coli Strains

“…Bacteriocins translated from ORF010 and ORF023 were less than 10 kDa and exhibited similarity with the β-chain of enterocin X, a class IIb bacteriocin (Hu et al, 2010). Interestingly, the GxxxG motif present in the amino acid sequence of bacteriocins encoded by ORF010 and ORF023 have been shown to play a role in the sec-independent export machinery of enterocin X (Nissen-Meyer et al, 2010;Escamilla-Martínez et al, 2017). Of note, ORF010 and ORF012 were separated only by 28 nucleotides, suggesting that their bacteriocins can be affiliated to class IIb.…”

“…Of note, these new bacteriocins have only 24 common amino acids with the β-chain of Enterocin-X (Figure 3). The ORF012 may be translated into a bacteriocin similar to the ComC/BlpC leadercontaining pheromone/bacteriocin family (Wang et al, 2018), while ORF023 matches with bacteriocins of the lactobin A/cerein 7B family (Escamilla-Martínez et al, 2017). The bacteriocin predicted from the ORF030 is 33% similar with carnobacteriocin B2 and a class IIa immunity protein (Quadri et al, 1995).…”

Genome sequencing of Enterococcus faecium NT04, an oral microbiota revealed the production of enterocin A/B active against oral pathogens

“…Furthermore, our strain NT04 was able to produce both enterocin A and enterocin B. Enterocin A ( EntA ) is grouped as a class II bacteriocin [ 22 ]. It is synthesized by many strains of E. faecium [ 23 ].…”