Examinando por Autor "Sierra Zapata, Laura"
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Ítem Bacillus sp. strains and their inducible in vitro antagonism : a biochemical and molecular study(Universidad EAFIT, 2018) Sierra Zapata, Laura; Villegas Escobar, Valeska; Romero Tabarez, MagallyDiscovering novel antibiotic substances from natural sources and revitalizing the pipeline for screenings of naturally sourced substances that could render new bioactive compounds, is a priority nowadays in the face of a world crisis of antimicrobial resistance. This research was focused on disclosing an observed antagonism system composed of Bacillus sp. strains producing inducible antimicrobial activity against the plant pathogen Ralstonia solanacearum, a widespread bacterium that causes bacterial wilt disease to a great variety of plant species, including many agriculturally important ones as are bananas. The inducible phenomenon was discovered during the screening of 1493 aerobic endospore forming bacteria against plant pathogens. It was observed that in the presence of the chemical compound Triphenyl Tetrazolium Chloride (TTC), which belongs to the group of synthetic compounds known as tetrazolium salts used to monitor cell respiration, Bacillus sp. strains produced inhibition zones against the bacterial plant pathogen and other pathogenic bacterial species, while in the absence of the compound they did not have any bioactivity. During biochemical characterization, it was evidenced that although the phenomenon was observable across several species of the order Bacillales, strains belonging to B. cereus, B. pumilus and B. subtilis were outstanding in their inducible antagonism potential, among other species tested. Besides, relevant traits revealed that other tetrazolium salts did not induce antagonistic activity and that the addition of antioxidant compounds did not reduce the inducible antagonistic activity. Also, R. solanacearum sensitivity to antibiotics was not increased by the addition of TTC and the inducible activity was independent of the presence of the pathogenic strain. In order to determine genes and pathways that were activated under TTC conditions, transcriptomic and metabolomics analysis were performed. Transcriptomic results revealed that specific pathways of the nitrogen metabolism, such as pyrimidines, purines and histidine biosynthetic routes, were 2 to 5 fold up-regulated in B. subtilis NCIB-3610 cells growing under TTC presence. On the other hand, metabolomic analysis showed that 28 specific compounds were either unique or 3 to 5 fold more abundant in active extracts obtained from inducible conditions, compared to non-induced controls. Data mining on public chemical databases, using intrinsic properties of the selected compounds, suggests that they mostly belong to chemical families of carbamates, imidazoles, pyrrolidines, pyrimidines, dipeptides and oligopeptides, all of which are part of the nitrogen metabolism. Results suggest that Bacillus cells reduction of TTC into triphenyl formazan (TPF) and its further accumulation inside the cells, induces the production of nitrogen-derived compounds, either by activation of nitrogen metabolism biosynthetic pathways or by a biotransformation of TPF into derivatives. Once produced, the compounds are secreted into the medium and act as antimicrobials against other bacteria.Ítem Bioprospección de bacterias con actividad antibacteriana para el manejo de R. solanacearum a nivel de microcosmos(Universidad EAFIT, 2019) Valencia Vargas, Merlin Andrea; Sierra Zapata, Laura; Villegas Escobar, Valeska; Villegas Escobar, ValeskaÍtem Lipopeptides from Bacillus sp. EA-CB0959: Active metabolites responsible for in vitro and in vivo control of Ralstonia solanacearum(Academic Press Inc., 2018-07-31) Villegas Escobar, Valeska; González-Jaramillo LM; Ramirez, Maria; MONCADA, RUTH NATALIA; Sierra Zapata, Laura; Orduz, Sergio; Romero, Magally; Universidad EAFIT. Departamento de Ciencias; Ciencias Biológicas y Bioprocesos (CIBIOP)Broadening the spectrum of action of microbial bioactive compounds is a priority nowadays. From a collection of 1493 aerobic endospore forming bacteria, 3.1% (47) inhibited Serratia marcescens and were highly active against R. solanacearum. Thirty-six of these strains were identified as part of the ‘Operational Group B. amyloliquefaciens’ denoting the potential of strains from these species to produce antibacterial substances. Specifically, the strain Bacillus sp. EA-CB0959 was selected for further trials. Three families of lipopeptides: surfactins, iturins and fengycins were found as the active compounds produced by this strain. The highest bioactivity, produced by fengycins, had a minimal inhibitory concentration of 32 µg/mL. Treating greenhouse banana plants with a mixed fraction of lipopeptides reduced by 35% the incidence of Moko disease caused by R. solanacearum. Here we provide first time evidence of in vitro antibacterial activity of purified fengycins and in vivo activity of mixed lipopetides against Moko disease in banana plants. © 2018 Elsevier Inc.Ítem Reviewing microbial behaviors in ecosystems leading to a natural quorum quenching occurrence(INST TECNOLOGIA PARANA, 2017-01-01) Sierra Zapata, Laura; Romero Tabarez, Magally; Correa Alvarez, Javier; Villegas Escobar, Valeska; Universidad EAFIT. Departamento de Ciencias; Biodiversidad, Evolución y ConservaciónQuorum sensing is considered one of the most important discoveries in cell-to-cell communication. Although revealed in Bacteria, it has been identified as well as a mechanism present in the other two domains, Eukaryota and Archaea. This phenomenon consists mainly of an exchange and sensing of "words" produced by each cell: chemical signals known as autoinducers. The process takes places at high cell densities and confined environments, triggering the expression of specific genes that manifest in a determined phenotype. Quorum sensing has a fundamental importance in the organisms' fitness in natural ecosystems since it activates many of the traits needed by cells to survive under specific conditions, and thus a wide variety of chemical signals, which are detailed throughout the review, have evolved in response to the needs of an organism in the ecosystem it inhabits. As a counterpart, derived from the natural occurrence of quorum sensing, comes it's antagonistic process named quorum quenching. Acting in the exact opposite way, quorum quenching interferes or degrades the autoinducers confusing and stopping communication, hence affecting transcriptional regulation and expression of a specific phenotype. The main reasons for stopping this mechanism go from fading their own signals when perceiving scarce nutrients conditions, to degrading competitors' signals to take advantage in the ecosystem. Some of the most studied purposes and means known up to date to be used by cells for making quorum quenching in their ecosystems is what will be discussed along this review, offering information for future works on quorum quencher molecules bioprospection.Ítem Reviewing microbial behaviors in ecosystems leading to a natural quorum quenching occurrence(INST TECNOLOGIA PARANA, 2017-01-01) Sierra Zapata, Laura; Romero Tabarez, Magally; Correa Alvarez, Javier; Villegas Escobar, Valeska; Universidad EAFIT. Departamento de Ciencias; Ciencias Biológicas y Bioprocesos (CIBIOP)Quorum sensing is considered one of the most important discoveries in cell-to-cell communication. Although revealed in Bacteria, it has been identified as well as a mechanism present in the other two domains, Eukaryota and Archaea. This phenomenon consists mainly of an exchange and sensing of "words" produced by each cell: chemical signals known as autoinducers. The process takes places at high cell densities and confined environments, triggering the expression of specific genes that manifest in a determined phenotype. Quorum sensing has a fundamental importance in the organisms' fitness in natural ecosystems since it activates many of the traits needed by cells to survive under specific conditions, and thus a wide variety of chemical signals, which are detailed throughout the review, have evolved in response to the needs of an organism in the ecosystem it inhabits. As a counterpart, derived from the natural occurrence of quorum sensing, comes it's antagonistic process named quorum quenching. Acting in the exact opposite way, quorum quenching interferes or degrades the autoinducers confusing and stopping communication, hence affecting transcriptional regulation and expression of a specific phenotype. The main reasons for stopping this mechanism go from fading their own signals when perceiving scarce nutrients conditions, to degrading competitors' signals to take advantage in the ecosystem. Some of the most studied purposes and means known up to date to be used by cells for making quorum quenching in their ecosystems is what will be discussed along this review, offering information for future works on quorum quencher molecules bioprospection.