Actividad antibacteriana de actinomicetos frente a Escherichia coli y Staphylococcus aureus multirresistentes de origen hospitalario / Antibacterial activity of actimycetes against multiresistant Escherichia coli and Staphylococcus aureus isolated from a hospital

Introducción: La resistencia a los antimicrobianos (RAM) es un problema de salud pública que manifiesta la disminuida eficacia de estos agentes en la prevención y tratamiento de una proporción cada vez más amplia de patologías. Los actinomicetos son un grupo bacteriano importante de productores de metabolitos activos contra patógenos. Objetivo: Aislar actinomicetos del bosque tropical de Nariño, con potencial producción de metabolitos inhibitorios contra bacterias multidrogo-resistentes. Materiales y métodos: Se tomaron muestras de suelo de Bosque Tropical Húmedo de la Reserva Natural del Río Ñambí, se analizaron microbiológica y molecularmente. Se estimuló la producción in vitro de metabolitos secundarios y evaluó el efecto inhibitorio de estos extractos contra las bacterias multidrogo-resistentes Escherichia coli y Staphylococcus aureus. Resultados: Se obtuvieron 11 aislados presuntivos, se confirmó que cuatro de ellos correspondieron al género Streptomyces sp. Las pruebas de inhibición contra bacterias multidrogo-resistentes E. coli y S. aureus, permitieron verificar que el aislado P3772 fue el más eficiente en la inhibición de los patógenos. Conclusiones: Todos los actinomicetos evaluados presentan actividad antibacteriana contra al menos una de las bacterias patógenas estudiadas; destacando el aislado P3772, que inhibe a E. coli y S. aureus. Se espera caracterizar los compuestos vinculados a la actividad antibacteriana.

Introduction: Antimicrobial resistance (AR) is a public health problem that reveals the diminished efficacy of these agents in the prevention and treatment of an increasingly larger number of pathologies. Actinomycetes are an important bacterial producer group of metabolites that are active against pathogens. Objective: To isolate actinomycetes from the tropical forest of Nariño (Colombia), which have the potential to produce inhibitory metabolites against multi-drug resistant bacteria. Materials and methods: Soil samples were taken from the Humid Tropical Forest of the Río Ńambí Natural Reserve and analyzed through microbiological and molecular assays. In vitro production of secondary metabolites was first stimulated, followed by the assessment of the inhibitory effect of these extracts against multi-drug resistant Escherichia coli and Staphylococcus aureus. Results: 11 presumptive isolates were obtained, confirming that four of them corresponded to the Streptomyces sp. genus. The bacterial isolate P3772 was identified as the one with the highest inhibitory effect against multi-drug resistant E. coli and S. aureus. Conclusions: All the actinomycetes evaluated presented antibacterial activity. The isolate P3772 stands out, which inhibited both E. coli and S. aureus. The compounds associated with this antibacterial activity will be characterized in future studies.

Polyhydroxyalkanoate biosynthesis by oxalotrophic bacteria from high Andean soil / Biosíntesis de polihidrxialcanoato por bacterias oxalotróficas de suelos altoandinos / Biossínteses de polihidroxialcanoato por bactérias oxalotróficas de solos andinos

Abstract Oxalate is a highly oxidized organic acid anion used as a carbon and energy source by oxalotrophic bacteria. Oxalogenic plants convert atmospheric CO2 into oxalic acid and oxalic salts. Oxalate-salt formation acts as a carbon sink in terrestrial ecosystems via the oxalate-carbonate pathway (OCP). Oxalotrophic bacteria might be implicated in other carbon-storage processes, including the synthesis of polyhydroxyalkanoates (PHAs). More recently, a variety of bacteria from the Andean region of Colombia in Narino have been reported for their PHA-producing abilities. These species can degrade oxalate and participate in the oxalate-carbonate pathway. The aim of this study was to isolate and characterize oxalotrophic bacteria with the capacity to accumulate PHA biopolymers. Plants of the genus Oxalis were collected and bacteria were isolated from the soil adhering to the roots. The isolated bacterial strains were characterized using biochemical and molecular biological methods. The consumption of oxalate in culture was quantified, and PHA production was monitored in batch fermentation. The polymeric composition was characterized using gas chromatography. Finally, a biosynthetic pathway based on our findings and on those from published sources is proposed. Strains of Bacillus spp. and Serratia sp. were found to metabolize calcium oxalate and synthesize PHA.

Resumen El oxalato es un anión de ácido orgánico altamente oxidado usado como fuente carbono y energía por bacterias oxalotróficas. Las plantas oxalogénicas convierten CO2 atmosférico en ácido oxálico y sales oxálicas. La formación de sales de oxalato actúa como un sumidero de carbono en ecosistemas terrestres via oxalato-carbonato (OCP). Las bacterias oxalotróficas podrían estar implicadas en otros procesos de almacenamiento de carbono, incluyendo la síntesis de polihidroxialcanoatos (PHAs). Recientemente, una variedad de bacterias de la región andina colombiana en Nariño ha sido reportada por su habilidad para producir PHAs. Estas especies pueden degradar oxalato y participar en la vía del oxalato-carbonato. El objetivo de este estudio fue aislar y caracterizar bacterias oxalotróficas con capacidad de acumular biopolímeros PHA. Se colectaron plantas del genero Oxalis y se aislaron bacterias del suelo adheridas a las raíces. Las cepas bacterianas aisladas se caracterizaron usando métodos bioquímicos y de biología molecular. Se cuantificó el consumo de oxalato en cultivo, y se monitoreó la producción de PHA en fermentación por lotes. La composición polimérica se caracterizó usando cromatografía de gases. Finalmente, se propone una via biosintética basada en nuestros hallazgos y en los de otras fuentes publicadas. Se encontró que las cepas de Bacillus spp. y Serratia sp. metabolizan oxalato de calcio y sintetizan PHA.

Resumo O oxalato é um ânion de ácido orgânico altamente oxidado utilizado como fonte de carbono e nergía por bactérias oxalotróficas. As plantas oxalogênicas convertem CO2 atmosférico em ácido oxálico e sais oxálicos. A formação de sais de oxalato atua como um sumidouro de carbono em ecossistemas terrestres via oxalato-carbono (OCP). As bactérias oxalotróficas poderiam estar envolvidas em outros processos de armazenamento de carbono, incluindo a sínteses de polihidroxialcanoatos (PHAs). Recentemente, uma variedade de bactérias da região Andina colombiana no Departamento de Nariño foi reportada devido a sua habilidade para produzir PHAs. Estas espécies podem degradar oxalato e participar na via oxalato-carbono. O objetivo de esse estudo foi isolar e caracterizar bactérias oxalotróficas com capacidade de acumular biopolímeros PHA. Plantas do género Oxalis foram coletadas e se isolaram bactérias do solo aderido a suas raízes. As cepas bacterianas isoladas se caracterizaram utilizando métodos bioquímicos e de biologia molecular. O consumo de oxalato em cultivo foi quantificado, e a produção de PHA foi monitorada em fermentação por lotes. A composição polimérica se caracterizou utilizando Cromatografia de Gases. Finalmente, se propõe uma via biossintética baseada em nossos resultados juntamente com resultados da literatura. Se encontrou que as cepas de Bacillus spp. e Serratia sp. metabolizam oxalato de cálcio e sintetizam PHA.

Eficiencia en la reducción de Cromo por una bacteria silvestre en un tratamiento tipo Batch utilizando como sustrato agua residual del municipio de Pasto, Colombia / Efficiency in the reduction of chromium by a wild bacterium in a Batch treatment type using residual water substrate from the municipality of Pasto, Colombia

Resumen Objetivo: Evaluar la eficiencia en la reducción de Cromo en un tratamiento tipo Batch, utilizando como sustrato agua residual municipal inoculada con una bacteria silvestre. Materiales y métodos: Se verificó a escala de laboratorio el porcentaje de reducción de Cromo hexavalente de tres bacterias silvestres previamente aisladas de agua residual del Río Pasto (Bacillus thuringiensis, Bacillus amyloliquefaciens y Paenibacillus sp.); se seleccionó el aislado que presentó mayor porcentaje de reducción de Cr y fue sometido a diferentes tratamientos. El análisis de los resultados se hizo mediante estadística descriptiva. Resultados: B. thuringiensis, B. amyloliquefaciens, y Paenibacillus sp., presentaron porcentajes de reducción de Cr (VI) de 82,01%; 80,85% y 79,27%, respectivamente. Se determinó que el tercer tratamiento (agua sin esterilizar del Río Pasto con B. thuringiensis) presentó diferencias significativas respecto a los demás (p = 0,0001 α = 0,05), concluyendo que B. thuringiensis reduce en mayor proporción el Cr (VI), los resultados encontrados en esta investigación son promisorios en el campo de la biorremediación de efluentes contaminados con Cromo ya que pueden ser tomados como base para implementar estrategias de biorremediación a gran escala. Conclusión: La bacteria B. thuringiensis presentó alta eficiencia en la reducción de Cromo hexavalente (99,42%), cuando fue implementada en un tratamiento a escala de laboratorio de agua residual sin esterilizar.

Abstract Objective: To evaluate the efficiency in the reduction of chromium in a Batch treatment type, using municipal residual water substrate inoculated with a wild bacterium. Materials and methods: The reduction percentage of hexavalent chromium of three wild bacteria previously isolated from residual water from the Pasto River was verified at laboratory scale (Bacillus thuringiensis, Bacillus amyloliquefaciens and Paenibacillus sp.); the isolated that showed the highest percentage of reduction of Cr was selected and was subjected to different treatments. The analysis of results was done using descriptive statistics. Results: B. thuringiensis, B. amyloliquefaciens, and Paenibacillus sp., presented percentages of reduction of Cr (VI) of 82,01%; 80,85% and 79,27%, respectively. It was determined that the third treatment (nonsterile water from the Pasto River with B. thuringiensis) presented significant differences with regard to the other (p = 0.0001 α = 0.05), concluding that B. thuringiensis reduces in greater proportion the Cr (VI). The results found in this research are promising in the field of bioremediation of contaminated effluents with Chrome since they may be taken as the basis for implementing strategies of bioremediation on a large scale. Conclusion: The bacteria B. thuringiensis presented high efficiency in the reduction of hexavalent chromium (99.42%) when implemented in a treatment at laboratory scale of residual nonsterile water.

Diseño instruccional para argumentación científica en línea / Instructional design for scientific argumentation on line

El propósito de la investigación realizada fue evaluar la efectividad de la enseñanza de procesos estructurados de argumentación en el desarrollo de la argumentación científica de estudiantes inscritos en un curso virtual de Biotecnología. Con un diseño experimental se compararon dos grupos de estudiantes, solo uno recibió orientación sobre procesos de argumentación. Ambos grupos participaron en un foro de trabajo colaborativo en línea. En ambos grupos la evaluación de la competencia argumentativa se realizó aplicando el instrumento de evaluación para argumentación dialógica en línea, propuesta por Clark y Sampson (2008); este modelo consta de tres categorías: estructura argumentativa, calidad de la argumentación y nivel de oposición al que llega el grupo. Para realizar el experimento se construyó un diseño instruccional basado en la argumentación dialógica. El primer componente del diseño corresponde a la enseñanza del modelo argumentativo. El segundo elemento es el contexto de aprendizaje a partir del cual se desarrolla la interacción y el tercero corresponde a las mediaciones tecnológicas. El diseño instruccional se incorporó en el curso virtual de Biotecnología alojado en la plataforma tecnológica de la Universidad, la cual utiliza Moddle 2X. Los resultados indicaron que el 60% de los estudiantes del grupo experimental utilizó todas las categorías argumentativas de Toulmin; al contrario, ningún estudiante del grupo control obtuvo un nivel de estructuración con todas las categorías. Asimismo, la enseñanza explícita de procesos estructurados de argumentación provoca mejor desempeño en el foro de trabajo colaborativo en aspectos como nivel de calidad de los argumentos y nivel de oposición.

Teaching argumentation is a strategy of great interest within the community involve in the study of didactic in science since there are numerous studies showing the relationship between the development of scientific thought and the argumentation structured processes (Khun, 2008), however in virtual learning environments teaching argumentation is a relatively new issue and therefore constitutes a challenge for the instructional designer of the virtual course. Collaborative learning in virtual environments is a strategy implemented in recent years in such contexts under the assumption that computer-mediated and asynchronously communication facilitates the maintenance of dialogue (Schwarz & Glassner, 2003). However, studies indicate that these students' dialogues in virtual forums can be weak and based on beliefs not justified instead of using reasons articulated between theory and evidence, otherwise can be characterized because students within the group accept explanations without paying enough attention on the relationship between a statement and the available evidence and therefore readily accepted arguments without making opposition. This condition can be explained because in the context of collaborative internet the problems increase due to issues like complexity of interfaces, decreasing communication channels regarding classroom situations, or the ease of students to mask his inactivity within collaborative groups (Peñaloza, García & Espinoza, 2011). Although most researchers agree that the dialogic argumentation promotes the acquisition of scientific concepts, also they say it is difficult to integrate the teaching of argumentation structured processes into a virtual course of experimental science as well as evaluating appropriation of concepts through arguments. In this paper the results of an investigation conducted to evaluate the effectiveness of an instructional design based on structured argument process in the development of the argumentative capacity of higher education students enrolled in an online course biotechnology is presented. The population under investigation corresponds to higher education students of both sexes who are enrolled in a Biotechnology online course offered by a distance university in Colombia. Instructional design incorporated three elements: the first is the teaching of Toulmin argumentative model, the second element incorporated was the situated learning context from which the interaction is developed and for this study corresponds to a Biotechnology theme and the third component included the design and development of techno-didactic mediations to promote educational interactivity where virtual learning objects, guide activities and assessment rubrics were included. These elements were incorporated into the virtual course within the Moodle 2.1 platform. Moreover, learning strategy based on dialogic argument was developed in four stages: (a) scientific research, (b) argumentative paper development, (c) counter argument, and (d) scientific consensus. To evaluate the effectiveness of instructional design and online learning strategy based on dialogic argumentation an experimental design was conducted with a control group and post-test. The assessment of the argumentative capacity was performed by applying the online assessment tool for dialogic argumentation proposed by Clark and Sampson (2008). This model evaluates the argumentative process in the virtual forum both individually and group. Data were analyzed with non -parametric statistical tests. The research results indicated significant differences in the level of argumentative competence in the experimental group compared with the control group. The experimental group had higher ratings on their ability to structure texts, support arguments within the group and make reasoned opposition to reach consensus. Also, results of this research support the design and learning strategy based on the argument for virtual environments and shown it can be effective to increase the academic performance of students participating in collaboration online forums. Students in the control group did not performed opposition, and, most students in the experimental group achieved level three opposition on the scale of Clark and Sampson (2008), this aspect indicates the need to develop strategies to increase the level of opposition.

Degradación de oxalato por bacterias oxalotróficas asociadas a plantas del género Oxalis sp en regiones Andinas del departamento de Nariño, Colombia / Oxalate degradation by oxalotrophic bacteria associated with plants of the genus Oxalis sp in the Andean region of the department of Nariño, Colombia

Introducción: El ácido oxálico (H2C2O4) y las sales de oxalato son sustancias altamente oxidadas y consideradas tóxicas para algunos sistemas biológicos, incluido el humano, no obstante, pueden ser utilizadas como fuente de carbono y energía por algunas comunidades bacterianas, denominadas oxalotróficas, las cuales por su capacidad metabólica forman parte de la ruta biogeoquímica oxalato-carbonato (OCP, oxalate-carbonate pathway). Objetivo: Aislar y caracterizar bacterias oxalotróficas a partir de plantas del género Oxalis sp., de zonas alto-andina de Nariño- Colombia. Materiales y métodos: Se recolectaron muestras de suelo rizosférico de plantas oxalogénicas que fueron analizadas con parámetros fisicoquímicos y se utilizó un medio selectivo Schlegel para el aislamiento de bacterias oxalotróficas. Resultados: Las bacterias aisladas en medio selectivo Schlegel fueron caracterizadas bioquímicamente como: (Serratia fonticola, Bacillus amyloliquefaciens, Bacillus subtilis, Bacillus vallismortis y Bacillus cereus). Estas especies fueron capaces de degradar oxalato e incrementar el pH producto de la degradación. Conclusión: Este tipo de bacterias pueden ser estudiadas en trabajos complementarios para evaluar su potencial como biofertilizantes y/o alternativas de bioremediación en suelos ácidos. El estudio a pesar de ser indicativo a nivel biológico, puede en un futuro y con base en mayores soportes en investigación, tornarse en una promisoria aplicación para reducir el oxalato de calcio en los alimentos de consumo diario que presentan un renglón de importancia agrícola en la región, potencialmente dañinos para la función renal.

Introduction: Oxalic acid (H2C2O4) and oxalate salts are highly oxidized substances, which are considered as toxic for some biological systems, including the human being; however, they can be used as a source of carbon and energy for some bacterial communities called oxalotrophic which are part of the so called oxalate-carbonate geochemistry pathway (OCP) due to its metabolic capacity. Objective: The aim of this research was to isolate and characterize oxalotrophic bacteria from plants of the genus Oxalis sp. in the high-andean zone of the department of Nariño, Colombia. Materials and methods: Samples of rhizosphere soil from oxalogenic plants were analyzed with physicochemical parameters and a Schlegel selective medium was used to isolate oxalotrophic bacteria. Results: The isolated bacteria through Schlegel selective medium were identified biochemically as: (Serratia fonticola, Bacillus amyloliquefaciens, Bacillus subtilis, Bacillus vallismortis and Bacillus cereus). The identified species play an important role in the rhizosphere soil, principally for the capacity to increase the pH during oxalate consumption. Conclusion: This type of bacteria can be studied in additional studies to evaluate their potential as bio-fertilizers and/or bioremediation alternatives in acid soils. Despite that the study is indicative at a biological level, it can become a promising application, in the future and with greater support in research, to reduce the calcium oxalate in food of daily consumption which represent an agricultural important line in the region and are potentially harmful to kidney finction.