Numerical taxonomy of heavy metal-tolerant nonhalophilic bacteria isolated from hypersaline environments

A total of 232 metal-tolerant bacterial strains were isolated from water and sediment samples collected in different hypersaline environments located in Cádiz, Huelva and Morón de la Frontera (Spain). They were isolated on a medium containing mercury, chromium, cadmium, copper or zinc. These halotolerant isolates were analyzed by numerical taxonomy techniques by using the simple matching (SSM) and Jaccard (SJ) coefficients; clustering was achieved using the unweighted pair group method with averages (UPGMA) algorithm. At the 81% and 83% similarity level, different numbers of phenons were obtained for Gram-negative and Grampositive halotolerant microorganisms. Most of the 48 Gram-negative metal-tolerant strains studied were grouped into nine phenons, representing the genera Pseudoalteromonas, Alteromonas, Xanthomonas, Pseudomonas, Alcaligenes and Enterobacteria. The 72 Gram-positive metal-tolerant strains grouped into eight phenons, with only 15 strains left unassigned. Most of the isolates were assigned to the genus Bacillus (seven phenons), and one phenon comprised microorganisms with phenotypic characteristics similar to those of the genus Celullomonas

Quantitative RNA-seq Analysis Unveils Osmotic and Thermal Adaptation Mechanisms Relevant for Ectoine Production in Chromohalobacter salexigens

Quantitative RNA sequencing (RNA-seq) and the complementary phenotypic assays were implemented to investigate the transcriptional responses of Chromohalobacter salexigens to osmotic and heat stress. These conditions trigger the synthesis of ectoine and hydroxyectoine, two compatible solutes of biotechnological interest. Our findings revealed that both stresses make a significant impact on C. salexigens global physiology. Apart from compatible solute metabolism, the most relevant adaptation mechanisms were related to “oxidative- and protein-folding- stress responses,” “modulation of respiratory chain and related components,” and “ion homeostasis.” A general salt-dependent induction of genes related to the metabolism of ectoines, as well as repression of ectoine degradation genes by temperature, was observed. Different oxidative stress response mechanisms, secondary or primary, were induced at low and high salinity, respectively, and repressed by temperature. A higher sensitivity to H2O2 was observed at high salinity, regardless of temperature. Low salinity induced genes involved in “protein-folding-stress response,” suggesting disturbance of protein homeostasis. Transcriptional shift of genes encoding three types of respiratory NADH dehydrogenases, ATP synthase, quinone pool, Na+/H+ antiporters, and sodium-solute symporters, was observed depending on salinity and temperature, suggesting modulation of the components of the respiratory chain and additional systems involved in the generation of H+ and/or Na+ gradients. Remarkably, the Na+ intracellular content remained constant regardless of salinity and temperature. Disturbance of Na+- and H+-gradients with specific ionophores suggested that both gradients influence ectoine production, but with differences depending on the solute, salinity, and temperature conditions. Flagellum genes were strongly induced by salinity, and further induced by temperature. However, salt-induced cell motility was reduced at high temperature, possibly caused by an alteration of Na+ permeability by temperature, as dependence of motility on Na+-gradient was observed. The transcriptional induction of genes related to the synthesis and transport of siderophores correlated with a higher siderophore production and intracellular iron content only at low salinity. An excess of iron increased hydroxyectoine accumulation by 20% at high salinity. Conversely, it reduced the intracellular content of ectoines by 50% at high salinity plus high temperature. These findings support the relevance of iron homeostasis for osmoadaptation, thermoadaptation and accumulation of ectoines, in C. salexigens.España Ministerio de Economía y Competitividad BIO2015-63949-RJunta de Andalucía P11-CVI-729

LA RELACIÓN RENTABILIDAD-RIESGO EN UN CONTEXTO DE INFORMACIÓN ASIMÉTRICA: UNA APLICACIÓN AL MERCADO ESPAÑOL

The aim of this paper consists on seeing whether the information differential affects tothe stocks return in the Spanish market. Usually the firm attention by financial analysts,expressed by de number of earnings estimations, has been used as a proxy of the differentialinformation. Nevertheless, in this paper we use a different point of view based in the approachof Hong, Lim and Stein (2000). In particular, given the close relation between the firm size andthe analysts’ number following the firm, we use residual from the regression of the number onanalysts following a firm on size as a proxy of the information differential. The results show,firstly, that the CAPM cannot explain the return difference among portfolios constructed by theresidual coverage level. With this evidence, the next step is to explain how the informationdifferential can affect the stock return level. El objetivo de este trabajo consiste en comprobar si, en el ámbito del mercado español, la existencia de información diferencial afecta al nivel de rentabilidad de los títulos. En muchos trabajos es práctica habitual emplear como proxy del diferencial de información el grado de seguimiento de las empresas por parte de los analistas financieros, medido éste por el número de estimaciones anuales de beneficios que emiten. Sin embargo, en este trabajo se sigue un enfoque diferente basado en el planteamiento propuesto por Hong, Lim y Stein (2000). En particular, dada la estrecha relación existente entre el número de analistas que siguen a una empresa y el tamaño de ésta, se utiliza como proxy del diferencial de información la cobertura residual por parte de los analistas que se obtiene como residuo de la regresión entre el número de analistas que siguen a una empresa y su tamaño. La evidencia obtenida, en un primer momento, indica que el CAPM no es capaz de explicar las diferencias de rentabilidad observadas entre las carteras construidas por el nivel de cobertura residual. Tras obtener este resultado, el siguiente paso consiste en explicar la forma en que el diferencial de información afecta al nivel de rentabilidad.IBES, analistas financieros, diferencial de información, cobertura residual IBES, financial analysts, information differential, residual coverage.

Numerical taxonomy of heavy metal-tolerant nonhalophilic bacteria isolated from hypersaline environments

A total of 232 metal-tolerant bacterial strains were isolated from water and sediment samples collected in different hypersaline environments located in Cádiz, Huelva and Morón de la Frontera (Spain). They were isolated on a medium containing mercury, chromium, cadmium, copper or zinc. These halotolerant isolates were analyzed by numerical taxonomy techniques by using the simple matching (SSM) and Jaccard (SJ) coefficients; clustering was achieved using the unweighted pair group method with averages (UPGMA) algorithm. At the 81% and 83% similarity level, different numbers of phenons were obtained for Gram-negative and Grampositive halotolerant microorganisms. Most of the 48 Gram-negative metal-tolerant strains studied were grouped into nine phenons, representing the genera Pseudoalteromonas, Alteromonas, Xanthomonas, Pseudomonas, Alcaligenes and Enterobacteria. The 72 Gram-positive metal-tolerant strains grouped into eight phenons, with only 15 strains left unassigned. Most of the isolates were assigned to the genus Bacillus (seven phenons), and one phenon comprised microorganisms with phenotypic characteristics similar to those of the genus Celullomonas

Light as an energy source in continuous cultures of bacteriorhodopsin-containing halobacteria

The role of light as an energy source for slightly aereated cultures of halobac­ teria was studied, using continuous cultures with low nutrient concentrations and a low oxygen supply. A series of experiments were carried out with non­ illuminated and differently illuminated cultures and with ditferent oxygen transfer rates. Under low oxygen availability, light proved to be a decisively important energy source that allowed the populations to reach higher growth rates and much higher population densities. Oxygen inftuenced the growth over only a minimal level, below which neither the illuminated nor the dark cultures were atfected by the oxygen transfer rate. From these results, it appears that the bacteriorhodop­ sin-mediated energy supply could have a very important role for the ecology of halobacteria in their microaerophilic habitats. In the illuminated cultures, cells that originated purple colonies on plates appeared. These cells, which could be bacteriorhodopsin-constitutive mutants, are now being studied

Susceptibility of halobacteria to heavy metals

Sixty-eight halobacteria, including both culture coUection strains and fresh isolates from widely dift'ering geographical areas, were tested for susceptibility to arsenate, cadmium, chromium, cobalt, copper, lead, mercury, nickel, silver, and zinc ions by an agar dilution technique. The culture collection strains showed dift'erent susceptibilities, clustering into five groups. Halobacterium medilerranei and Halobacterium volcanii were the most metal tolerant, whereas Haloarcula californiae and Haloarcula sinaiiensis had the highest susceptibilities of the culture collection strains. Dift'erent patterns of metal susceptibility were found for all the halobacteria tested, and there was a uniform susceptibility to mercury and silver. All strains tested were multiply metal tolerant

Emisiones de gases de invernadero en España (1990-2006)

EL CAMBIO CLIMÁTICO III CONGRESO ANDALUZ DE DESARROLLO SOSTENIBLE VII CONGRESO ANDALUZ DE CIENCIAS AMBIENTALE

Dimensión fractal en el aula con obras del Museo Thyssenbornemisza

A través de distintas actividades, hemos comprobado que los fractales son siempre una potente herramienta de motivación en el aula. Mostramos una novedosa investigación realizada con alumnos de 2º de ESO en la que se relaciona el concepto de dimensión fractal con las líneas presentes en un cuadro, en este caso en obras seleccionadas del Museo Thyssen-Bornemisza. Tras una presentación de los conceptos de fractal y de dimensión fractal, se muestra una propuesta de trabajo en la que cada alumno selecciona una obra y realiza los pasos diseñados para estimar la dimensión fractal de la obra. Presentamos el método de trabajo y los resultados obtenidos con la finalidad de comparar la “cantidad de líneas” en las obras estudiadas

Matemáticas y plástica, juntas y revueltas. Disfrutando con actividades interdisciplinares a partir de obras del Museo Thyssen-Bornemisza

Presentamos, desde una perspectiva interdisciplinar, un taller de variadas actividades con el objetivo de constatar las numerosas e interesantes relaciones entre las Matemáticas y la Plástica. Queremos que nuestros alumnos disfruten con las Matemáticas descubriendo, de una manera lúdica y atractiva, algunas de las muchas interacciones con el arte partiendo de obras seleccionadas en el Museo Thyssen-Bornemisza. La variedad de actividades diseñadas a partir de obras de grandes artistas como Pollock, Mondrian o Kandisky nos llevan a plasmar nuestra proporción áurea en un obra, a trabajar con fractales o incluso a crear una obra colaborativa a ritmo de Fangoria y de su “Geometría Polisentimental”