title: Purification and genetic characterization of gassericin E, a novel co-culture inducible bacteriocin from Lactobacillus gasseri EV1461 isolated from the vagina of a healthy woman.
abstract: BACKGROUND
  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.
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Food Biotechnology, Instituto de la Grasa, Consejo Superior de Investigaciones Científicas (CSIC), Sevilla, Spain. maldoantonio@gmail.com.|Department of Nutrition, Food Science and Food Technology, Complutense University of Madrid, Madrid, Spain. maldoantonio@gmail.com.|Present address: Department of Food Biotechnology, Instituto de la Grasa (CSIC), Campus Universidad Pablo de Olavide, Edificio 46. Carretera de Utrera, Km 1, 41013, Seville, Spain. maldoantonio@gmail.com.
authors.forename: Antonio
authors.initials: A
authors.lastname: Maldonado-Barragán
authors.affiliation: Department of Food Biotechnology, Instituto de la Grasa, Consejo Superior de Investigaciones Científicas (CSIC), Sevilla, Spain.
authors.forename: Belén
authors.initials: B
authors.lastname: Caballero-Guerrero
authors.affiliation: Department of Nutrition, Food Science and Food Technology, Complutense University of Madrid, Madrid, Spain.
authors.forename: Virginia
authors.initials: V
authors.lastname: Martín
authors.affiliation: Department of Food Biotechnology, Instituto de la Grasa, Consejo Superior de Investigaciones Científicas (CSIC), Sevilla, Spain.
authors.forename: José Luis
authors.initials: JL
authors.lastname: Ruiz-Barba
authors.affiliation: Department of Nutrition, Food Science and Food Technology, Complutense University of Madrid, Madrid, Spain.
authors.forename: Juan Miguel
authors.initials: JM
authors.lastname: Rodríguez
mesh_terms: D000328:Adult; D000900:Anti-Bacterial Agents / Q000302:isolation & purification* / Q000378:metabolism / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001430:Bacteriocins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism / Q000494:pharmacology*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007778:Lactobacillus / Q000737:chemistry / Q000145:classification / Q000302:isolation & purification / Q000378:metabolism*; D014621:Vagina / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D001430:Bacteriocins
keywords: Bacteriocin; Gassericin; Quorum sensing; Three-component regulatory system