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

BMC Microbiology, Mar 2016

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.

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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

Maldonado-Barragán et al. BMC Microbiology 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 Antonio Maldonado-Barragán 0 1 2 3 Belén Caballero-Guerrero 1 3 Virginia Martín 0 José Luis Ruiz-Barba 1 3 Juan Miguel Rodríguez 0 0 Department of Nutrition, Food Science and Food Technology, Complutense University of Madrid , Madrid , Spain 1 Department of Food Biotechnology, Instituto de la Grasa , Consejo Superior de Investigaciones Científicas (CSIC), Sevilla , Spain 2 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 3 Department of Food Biotechnology, Instituto de la Grasa , Consejo Superior de Investigaciones Científicas (CSIC), Sevilla , Spain 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). (Continued on next page) - (Continued from previous page) 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. Background Members of the genus Lactobacillus are widely recognized as the hallmark of the normal or healthy vagina and are thought to play a major role in protecting the vaginal environment from non-indigenous and potentially harmful microorganisms [ 1–4 ]. Lactobacillus gasseri is a human autochthonous microorganism [5] and one of the dominant Lactobacillus species in the vaginal ecosystem, together with Lactobacillus jensenii, Lactobacillus iners and Lactobacillus crispatus [ 6–8 ]. Thus, decreasing of lactobacilli titer in the vagina, results in bacterial vaginosis (BV), where the normal flora is replaced by undesirable bacteria, including bacterial pathogens such Gardnerella vaginalis, Atopobium vaginae, Mobiluncus curtisii, Prevotella bivia, Leptotrichia amnionii, Eggerthella spp,, Sneathia spp and Megasphaera type I spp. [ 9–11 ]. L. gasseri has been well documented as a commensal of the vaginal mucosa and exhibits a negative correlation with BV [ 2–4 ]. Some strains of this species have a high potential for being used as probiotics in order to maintain vaginal homeostasis [ 12–14 ]. L. gasseri may confer colonization resistance against pathogens in the vagina by displacing them through competitive adhesion [ 15, 16 ] or by direct inhibition through production of antimicrobial compounds, including lactic acid, hydrogen peroxide and bacteriocins [ 12, 17 ]. Bacteriocins could play a major role to control non-indigenous or pathogenic org (...truncated)


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Antonio Maldonado-Barragán, Belén Caballero-Guerrero, Virginia Martín, José Ruiz-Barba, Juan Rodríguez. 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, BMC Microbiology, 2016, pp. 37, 16, DOI: 10.1186/s12866-016-0663-1