Escamilla-Martínez E E, Cisneros Y M Álvarez, Fernández F J, Quirasco-Baruch M, Ponce-Alquicira E
Division de Ciencias Biológicas y de la Salud, UAM Iztapalapa, Avenida San Rafael Atlixco No. 186, Col. Vicentina, Iztapalapa, 09340, Mexico City (ORCID: http://orcid.org/0000-0003-4676-1828 [F.J.F.]).
Facultad de Química UNAM, Avenida Universidad No. 3000, Universidad Nacional Autónoma de México, C. U. Coyoacán, 04510, Mexico City, Mexico.
J Food Prot. 2017 Nov 1;80(11):1851-1856. doi: 10.4315/0362-028X.JFP-17-039.
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.
从发酵香肠中分离出的屎肠球菌菌株MXVK29产生一种分子量为3.5 kDa的细菌素，根据其末端氨基酸序列，该细菌素属于肠球菌素II.1类，并已被鉴定为肠球菌素A。这种细菌素对李斯特菌、葡萄球菌、片球菌和肠球菌的选定菌株具有活性。在本研究中，我们鉴定了与该细菌素结构基因相邻的基因，如免疫基因（entI）和诱导基因（entF）。此外，还鉴定了该细菌素的辅助基因，如entK、entR和entT，以及orf2和orf3，它们与IIb类肽细菌素具有高度同源性。orf2显示出与PlnNC8α、EntCα和Ent1071A等细菌素相似的共有基序GxxxG，而orf3显示出与PlnNC8β（AxxxA）中存在的共有基序SxxxS相似。PlnNC8仅在细菌共培养物中表达，因此这种双肽细菌素的表达有可能通过类似机制诱导。到目前为止，在该菌株中仅发现了肠球菌素A的表达；然而，ent29α和ent29β基因的存在为进一步研究其诱导、功能和起源提供了可能性。尽管在其他屎肠球菌菌株中有关于这种类型细菌素（EntX、EntC和Ent1071）的报道，但尚未有关于产生两种不同类型细菌素的肠球菌菌株的报道。
