Maldonado-Barragán Antonio, Caballero-Guerrero Belén, Martín Virginia, Ruiz-Barba José Luis, Rodríguez Juan Miguel
Department of Food Biotechnology, Instituto de la Grasa, Consejo Superior de Investigaciones Científicas (CSIC), Sevilla, Spain.
Department of Nutrition, Food Science and Food Technology, Complutense University of Madrid, Madrid, Spain.
BMC Microbiol. 2016 Mar 12;16:37. doi: 10.1186/s12866-016-0663-1.
Lactobacillus gasseri is one of the dominant Lactobacillus species in the vaginal ecosystem. Some strains of this species have a high potential for being used as probiotics in order to maintain vaginal homeostasis, since they may confer colonization resistance against pathogens in the vagina by direct inhibition through production of antimicrobial compounds, as bacteriocins. In this work we have studied bacteriocin production of gassericin E (GasE), a novel bacteriocin produced by L. gasseri EV1461, a strain isolated from the vagina of a healthy woman, and whose production was shown to be promoted by the presence of certain specific bacteria in co-culture. Biochemical and genetic characterization of this novel bacteriocin are addressed.
We found that the inhibitory spectrum of L. gasseri EV1461 was broad, being directed to species both related and non-related to the producing strain. Interestingly, L. gasseri EV1461 inhibited the grown of pathogens usually associated with bacterial vaginosis (BV). The antimicrobial activity was due to the production of a novel bacteriocin, gassericin E (GasE). Production of this bacteriocin in broth medium only was achieved at high cell densities. At low cell densities, bacteriocin production ceased and only was restored after the addition of a supernatant from a previous bacteriocin-producing EV1461 culture (autoinduction), or through co-cultivation with several other Gram-positive strains (inducing bacteria). DNA sequence of the GasE locus revealed the presence of two putative operons which could be involved in biosynthesis and immunity of this bacteriocin (gaeAXI), and in regulation, transport and processing (gaePKRTC). The gaePKR encodes a putative three-component regulatory system, involving an autoinducer peptide (GaeP), a histidine protein kinase (GaeK) and a response regulator (GaeR), while the gaeTC encodes for an ABC transporter (GaeT) and their accessory protein (GaeC), involved in transport and processing of the bacteriocin. The gaeAXI, encodes for the bacteriocin gassericin E (GasE), a putative peptide bacteriocin (GaeX), and their immunity protein (GaeI).
The origin of the strain (vagina of healthy woman) and its ability to produce bacteriocins with inhibitory activity against vaginal pathogens may be an advantage for using L. gasseri EV1461 as a probiotic strain to fight and/or prevent bacterial infections as bacterial vaginosis (BV), since it could be better adapted to live and compete into the vaginal environment.
加氏乳杆菌是阴道生态系统中占主导地位的乳杆菌种类之一。该物种的一些菌株具有很高的作为益生菌的潜力，可用于维持阴道内环境稳定，因为它们可能通过产生抗菌化合物（如细菌素）直接抑制作用，赋予对阴道病原体的定植抗性。在本研究中，我们研究了加氏乳杆菌EV1461产生的一种新型细菌素——加氏菌素E（GasE），该菌株从一名健康女性的阴道中分离得到，并且其产生在共培养中有某些特定细菌存在时会得到促进。我们还对这种新型细菌素进行了生化和遗传特性分析。
我们发现加氏乳杆菌EV1461的抑制谱很广，针对的是与产生菌株相关和不相关的物种。有趣的是，加氏乳杆菌EV1461抑制了通常与细菌性阴道病（BV）相关的病原体的生长。抗菌活性归因于一种新型细菌素——加氏菌素E（GasE）的产生。仅在高细胞密度下才能在肉汤培养基中产生这种细菌素。在低细胞密度下，细菌素产生停止，只有在添加先前产生细菌素的EV1461培养物的上清液（自诱导）或通过与其他几种革兰氏阳性菌株共培养（诱导细菌）后才能恢复。GasE基因座的DNA序列显示存在两个推定的操纵子，可能参与这种细菌素的生物合成和免疫（gaeAXI），以及调节、转运和加工（gaePKRTC）。gaePKR编码一个推定的三组分调节系统，涉及一种自诱导肽（GaeP）、一种组氨酸蛋白激酶（GaeK）和一种应答调节因子（GaeR），而gaeTC编码一种ABC转运蛋白（GaeT）及其辅助蛋白（GaeC），参与细菌素的转运和加工。gaeAXI编码细菌素加氏菌素E（GasE）、一种推定的肽细菌素（GaeX）及其免疫蛋白（GaeI）。
该菌株的来源（健康女性的阴道）及其产生对阴道病原体具有抑制活性的细菌素的能力，可能是将加氏乳杆菌EV1461用作益生菌菌株来对抗和/或预防诸如细菌性阴道病（BV）等细菌感染的一个优势，因为它可能更适应在阴道环境中生存和竞争。
