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Tolerance to cadmium of agave lechuguilla (agavaceae) seeds and seedlings from sites contaminated with heavy metals
Get PDF"We investigated if seeds of Agave lechuguilla from contaminated sites with heavy metals were more tolerant to Cd ions than seeds from noncontaminated sites. Seeds from a highly contaminated site (Villa de la Paz) and from a noncontaminated site (Villa de Zaragoza) were evaluated. We tested the effect of Cd concentrations on several ecophysiological, morphological, genetical, and anatomical responses. Seed viability, seed germination, seedling biomass, and radicle length were higher for the non-polluted site than for the contaminated one. The leaves of seedlings from the contaminated place had more cadmium and showed peaks attributed to chemical functional groups such as amines, amides, carboxyl, and alkenes that tended to disappear due to increasing the concentration of cadmium than those from Villa de Zaragoza. Malformed cells in the parenchyma surrounding the vascular bundles were found in seedlings grown with Cd from both sites. The leaves from the contaminated place showed a higher metallothioneins expression in seedlings from the control group than that of seedlings at different Cd concentrations. Most of our results fitted into the hypothesis that plants from metal-contaminated places do not tolerate more pollution, because of the accumulative effect that cadmium might have on them.
Effect of operational parameters on methanol biofiltration coupled with Endochitinase 42 production
Get PDF"En la presente tesis se estudió la biofiltración de metanol acoplada con la producción de proteínas heterólogas. Para ello, se utilizó un cultivo de P. pastoris transformado con el gen Ech42 responsable de producir la Endoquitinasa 42 de Trichoderma Atroviride (Pérez-Martínez et al., 2007). Se diseñaron tres biofiltros idénticos y se operaron bajo diferentes condiciones de carga de metanol, concentración de nitrógeno, pH y tiempo de residencia. La máxima capacidad de eliminación de metanol observada fue de 643.5 g/m3*h a una carga de metanol de 800 g/m3*h, 5 g/L (NH4)2SO4, pH 5 y 60 segundos de tiempo de residencia. La actividad de Ech42 varió entre 578 y 1172 U/L siendo el pH el parámetro más importante para el proceso. Además, se encontró que la capacidad de eliminación del sistema fue muy sensible a los cambios de condiciones manejadas. Sin embargo, la actividad de la proteína heteróloga fue notablemente estable. Por otro lado, también se estudió la divergencia del sistema a través de un análisis estadístico simple, microscopía electrónica de barrido y análisis cinético, durante las primeras tres etapas de operación. Se observó que dos o más sistemas de biofiltración pueden comportarse de distinta manera con el tiempo, aún y cuando son operados bajo las mismas condiciones. Algunas explicaciones probables son los procesos aleatorios de colonización de otras especias así como la impredecible evolución de comunidades microbianas. En cualquier caso, los resultados mostrados en esta tesis son el primer reporte de divergencia en biofiltros. Finalmente, se desarrolló un modelo matemático dinámico para describir el desempeño de los sistemas de biofiltración acoplados a la producción de proteínas. Éste se basó en ecuaciones para reactores CSTR (Completely Stirred Tank Reactor) pero en una estructura discretizada del sistema. Para la degradación de metanol se utilizó el modelo de Monod. Se consideró la presencia de dos grupos de microorganismos creciendo en los sistemas: P. pastoris y otros microorganismos. El modelo mostró un buen ajuste en relación con las capacidades de eliminación experimentales y la producción proteica. Sin embargo, fue difícil ajustar los valores experimentales de biomasa total presente (volumen). Tal discrepancia puede deberse a que el modelo no considera biomasa inerte. Por lo anterior, es recomendable que el modelo matemático sea modificado o replanteado.""In this thesis, methanol biofiltration coupled with heterologous protein production was studied. A P. pastoris strain transformed with the gen Ech42 responsible for producing Endochitinase 42 (Ech42) was used (Pérez-Martínez et al., 2007). Three different biofilters were designed and tested under different methanol loads, nitrogen concentrations, pH and EBRT (Empty Bed Residence Time) conditions. The maximum elimination capacity observed was 643.5 g/m3*h under a methanol load of 800 g/m3*h, 5 g/L (NH4)2SO4, pH 5 and 60 seconds of EBRT. Also, the Ech42 activity ranged from 578 to 1172 U/L and was mainly affected by pH changes. Additionally, it was observed that EC was very sensitive to changes under the mentioned operational conditions. However, the heterologous protein activity was quite stable. On the other hand, divergence in the system was approached. It was noted that two or more systems operating under identical conditions can behave differently over time. Thus, repeatability in biofiltration shouldn’t be taken for granted. Some probable explanations for such divergence are the random colonization of foreign species as well as the unpredictable evolution of microbial communities. In any case, this is the first report of operational divergence in biofilters. Finally, a dynamic mathematical model was developed based on CSTR equations. A Monod kinetic was used in order to describe methanol consumption behavior. Also, microbial growth was considered for two different kinds of microorganisms: P. pastoris and others. The model fit well with experimental elimination capacities and protein production. However, total biomass volume was not well described. The source of the model discrepancy could be the failure to consider inert biomass. Therefore, the mathematical model must be further explored.
Preservation of relevant properties of interconnected dynamical systems over complex networks
Get PDFDiscrete coupling and synchronization in the insulin release in the mathematical model of the B cells
No full text"The synchronization phenomenon that occurs in the Langerhans islets among pancreatic B cells is an interesting topic because these cells are responsible for the release of insulin in the blood stream. The aim of this work is to generate in-phase bursting electrical activity (BEA) in B cells with different behaviors such as active, inactive, and continuous spiking cells based on mathematical models using a discrete time coupling. The approach considers two steps, the former is a mechanism on how to force B cells to switch from silent phase to active, the latter is based on how to deal with in phase synchronization between active B cells. The coupling signal is triggered in discrete events caused by the crossing of a threshold of an active B cell which is given or defined by a Poincaré plane. The coupling on the inactive cells is applied to the state in which are the concentrations of agents which regulate the BEA. Based on numerical simulations, synchronization in the insulin release is obtained from B cells with different behaviors.
Microbial community composition of Tirez lagoon (Spain), a highly sulfated athalassohaline environment
Get PDF"Background: The aim was to study the seasonal microbial diversity variations of an athalassohaline environment with a high concentration of sulfates in Tirez lagoon (La Mancha, Spain). Despite the interest in these types of environments there is scarce information about their microbial ecology, especially on their anoxic sediments. Results: We report the seasonal microbial diversity of the water column and the sediments of a highly sulfated lagoon using both molecular and conventional microbiological methods. Algae and Cyanobacteria were the main photosynthetic primary producers detected in the ecosystem in the rainy season. Also dinoflagelates and filamentous fungi were identified in the brines. The highest phylotype abundance in water and sediments corresponded to members of the bacterial phylum Proteobacteria, mainly of the Gamma- and Alphaproteobacteria classes. Firmicutes and Actinobacteria were isolated and identified in Tirez brines and sediment samples. Halophilic sulfate reducing Deltaproteobacteria were also detected (Desulfohalobium). Conclusions: Important differences have been found in the microbial diversity present in the Tirez water column and the sediments between the wet and dry seasons. Also the Tirez lagoon showed a high richness of the bacterial Alpha- and Deltaproteobacteria, Bacteroidetes, Firmicutes, Actinobacteria and for the archaeal Euryarchaeota.
Adaptive control of robot manipulators with bounded inputs.
Get PDF"La tesis se enfoca en el diseño de leyes de control adaptables para robots manipuladores que consideran la naturaleza acotada de los actuadores. Se proponen esquemas generalizados para regulaci on y seguimiento globales por retroalimentacion de estados,cuyas estructuras permiten obtener versiones adaptables acotadas de algoritmos tipo PD previamente propuestos para el caso de conocimiento parametrico exacto.Tambien se diseño una ley de control tipo SP-SD por retroalimentacion de salida para la estabilizacion global de posicion. Con respecto a trabajos previos, los esquemas adaptables propuestos son los primeros que resuelven los problemas de control formulados: globalmente, sin involucrar discontinuidades, evitando saturacion de entrada y liberando las ganancias de control de restricciones para evitar el fenomeno de saturacion. Mas a un, ninguno de los esquemas propuestos esta restringido a usar una funcion de saturacion especta para lograr el acotamiento deseado sino que es posible escoger cualquiera dentro de un conjunto de funciones pasivas acotadas que incluye la tangente hiperbolica como caso particular. La escacia de los controladores propuestos es probada tanto en simulacion como experimentalmente.""This thesis focuses on the design of adaptive control schemes for robot manipulators under the consideration of the bounded nature of actuators. Generalized state-feedback controllers are proposed for global regulation and trajectory tracking, whose structures allow to obtain adaptive versions of bounded PD-type algorithms previously developed under the consideration of the exact knowledge of the system parameters. A globally stabilizing SP-SD-type output-feedback adaptive regulation scheme is also developed. With respect to previous works, the proposed adaptive controllers are the first to solve the formulated control problems: globally, free of discontinuities throughout the scheme, avoiding input saturation, and liberating the control gains from the satisfaction of saturation avoidance inequalities. Moreover, the developed controllers are not restricted to use a specic saturation function to achieve the required boundedness, but may involve any one within a set of bounded passive functions that include the hyperbolic tangent as a particular case. The efficiency of the proposed methodology was proven both through simulation and experimental implementations.
Nitrogen sources impact hydrogen production by Escherichia coli using cheese whey as substrate
Get PDF"The impact of nitrogen source on hydrogen production by Escherichia coli WDHL (Delta hycA Delta lacI) strain using cheese whey as a substrate was evaluated. To improve the assimilation of complex proteins such as lactalbumin, we assessed treatment with a protease. Also, five external nitrogen sources were tested: NH4Cl, (NH4)(2)SO4, urea, yeast extract, and tryptone. The treatments in 120 mL serological bottles with pancreatin 1000 mg/L produced 1.75-fold more hydrogen than the cultures without pancreatin. In the bottle cultures supplemented with yeast extract or tryptone 5 g/L, hydrogen production increased up to 3.2- and 3.5-fold, respectively, whereas inorganic salts and urea had no statistical difference with respect to the control cultures. In 1-L bioreactors, the use of tryptone improved 2.1-fold hydrogen production. Tryptone or yeast extract enable the total consumption of lactose in 40 h, whereas in the control assay the lactose was not completely consumed. Our results demonstrate that it is necessary to select an adequate nitrogen source, which allows both carbon source consumption and high hydrogen production.
Environmental applications of functionalized activated carbon with iron oxyhydroxide nanoparticles.
Get PDFTesis (Doctorado en Ciencias Ambientales)"El arsénico y el azufre son contaminantes prioritarios que determinan la calidad del agua y el aire. La remoción de arsénico y la desulfuración (de gas y diésel) mediante carbón activado es una opción atractiva como técnica de mitigación ambiental. Sin embargo, existen algunas limitaciones relacionadas con la capacidad y la selectividad de adsorción del carbón activado que deben ser superadas. La funcionalización del carbón activado con hidro(óxidos) de hierro tiene el potencial de remover selectivamente los contaminantes mencionados, sin embargo, el mayor reto durante la funcionalización del material es el anclaje de nanopartículas reactivas sobre su superficie. Este trabajo demostró que es posible reducir el tamaño de partícula de hidro(óxidos) de hierro anclados en carbón activado hasta 2 nm, mediante el uso de fosfato como agente acomplejante durante la hidrólisis forzada del cloruro férrico, que a su vez, permite que el material modificado adsorba arsénico y azufre de las fases líquida y gas. El material modificado tiene una elevada área específica de 900 m2/g y aproximadamente 1% de hierro, en la forma de pequeñas nanopartículas de hidro(óxidos) de aproximadamente 2 nm. Los resultados demostraron que el fosfato actúa únicamente como un agente acomplejante, disminuyendo el tamaño de partícula de los hidro(óxidos) de hierro y dejando los sitios activos disponibles para la adsorción de moléculas. La disminución en el tamaño de partículas (30 a 2 nm) ancladas en el carbón activado incrementó 60% la capacidad de adsorción de arsénico(V). Se propone que a pH 7, dos mecanismos de adsorción de arsénico(V) operan simultáneamente en materiales modificados con hierro: 1. intercambio de ligandos entre los arsenatos y las nanopartículas de hidro(óxidos) de hierro y 2. atracción electrostática entre arsenato y grupos superficiales básicos del adsorbente. Por otra parte, la funcionalización del carbón activado con hierro aumentó su capacidad de adsorción reactiva de dióxido de azufre en una corriente gaseosa. Nanopartículas de hierro brindaron una alta concentración de sitios de adsorción para las moléculas de dióxido de azufre y con esto, se incrementó la capacidad de adsorción en un 80%. Además, la incorporación de las nanopartículas de hidro(oxido) de hierro permitió la formación de Fe2(SO4)3 en la superficie del adsorbente, lo que contribuyó a una menor acidificación del medio después de la eliminación del dióxido de azufre.""Arsenic and sulfur are key pollutants whose presence determines the quality of water and air systems, respectively. Arsenic removal and desulfurization (of gas and diesel fuel) by activated carbon is an attractive option for pollution control. However, some limitations related to the capacity and selectivity of activated carbons must be overcome. The functionalization of activated carbon with iron oxyhydroxide has the potential of selectively removing those contaminants; however, a major challenge for material functionalization is the incorporation of reactive nanoparticles on its surface. This work demonstrated that it is possible to decrease the particle size, up to 2 nm, of iron oxyhydroxides anchored on activated carbon by using phosphate as a capping agent during ferric chloride forced hydrolysis, which in turn allowed the modified adsorbent to uptake arsenic and sulfur from liquid and gas phase. The modified material has a large surface area of 900 m2/g and a low iron content of about 1%, consisting of small nanoparticles of about 2 nm. The results demonstrated that phosphate is acting only as a capping agent, decreasing the particle size of iron oxyhydroxides and leaving the active sites on these available for adsorption of pollutants. The decrease in iron particle size from 30 to 2 nm, anchored on activated carbon led to an increase in arsenic(V) uptake of about 60%. It is also proposed that at pH 7 two arsenic(V) adsorption mechanisms can be carried out simultaneously in iron-modified activated carbons: a ligand interchange between arsenates and iron oxyhydroxide nanoparticles and electrostatic attraction between arsenate and the adsorbent basic surface groups. On the other hand, the functionalization of activated carbon with iron increased its reactive adsorption capacity of sulfur dioxide from gas phase. Iron nanoparticles provided highly dispersed adsorption sites for sulfur dioxide molecules and thus increased the adsorption capacity by about 80%. Furthermore, the incorporation of reactive iron oxyhydroxides enabled the formation of Fe2(SO4)3 on the adsorbents surface, which dismissed the acidification of the medium after sulfur dioxide elimination. The functionalization of activated carbons with iron nanoparticles was also effective for the adsorption and oxidation of sulfur compounds from model diesel fuel.
Heterogeneidad en la expresión de adhesinas y polimorfismos de SIR3 en una colección de aislados clínicos de Candida glabrata.
Get PDFTesis (Doctorado en Ciencias en Biología Molecular)"Candida glabrata ha surgido recientemente como la segunda causa más común de candidiasis invasiva en pacientes inmunocomprometidos, después de Candida albicans. La capacidad de adhesión de varias especies de Candida es importante para la colonización de mucosas. Bajo ciertas condiciones in vitro, la cepa de Candida glabrata (BG14) que estudiamos en el laboratorio, se adhiere a células epiteliales y endoteliales mediante las proteínas de pared celular Epa1, Epa6 y Epa7 (adhesinas epiteliales), codificadas por los genes EPA. Estos genes forman una familia de genes (de 17 a 23 según la cepa), la mayoría de los cuales se encuentran en regiones cercanas a los telómeros, y son regulados negativamente por las proteínas de la maquinaria del silenciamiento subtelomérico: Sir2, Sir3, Sir4, yKu70, yKu80, Rap1 y Rif1. En este trabajo caracterizamos la capacidad de adhesión a células epiteliales, o a superficies de plástico, de una colección de 79 aislados clínicos de C. glabrata, de diferentes orígenes. Once de ellos mostraron ser hiper-adherentes a células HeLa en condiciones en las que la cepa BG14 no se adhiere; sin embargo, casi todos tienen una capacidad de adherencia similar y uno de ellos mucha menor capacidad de formación de biofilms sobre superficies de plástico. La mayoría de los aislados hiperadherentes sobreexpresan uno o varios de los genes EPA.. En este trabajo amplificamos y secuenciamos los genes HDF1 y SIR3 de varios aislados hiperadherentes. Los datos muestran que el gen SIR3 de los aislados hiperadherentes tiene varios polimorfismos (silenciosos y/o con cambio de aminoácido) con respecto a la cepa BG14 y algunos de estos se localizan flanqueando regiones que en la proteína Sir3 de Saccharomyces cerevisiae son necesarias para el silenciamiento.""Candida glabrata has recently emerged as the second cause of candidiasis in immunocompromised patients after Candida albicans. Adherence to epithelial cells by Candida species is thought to be important for colonization of mucosal tissue. This adherence is mainly mediated by the cell wall proteins Epa1, Epa6 and Epa7 (called epithelial adhesins), encoded by the corresponding EPA genes. The EPA gene family is composed of 17 to 23 genes (depending on the strain), the majority of which are localized close to the telomeres and are negatively regulated by the silencing proteins Sir2, Sir3, Sir4, yKu70, yKu80, Rap1 and Rif1. In strain BG14, the majority of the EPA genes are not expressed in vitro due to subtelomeric silencing. In this work we characterized the ability to adhere to epithelial cells or plastic surfaces of a collection of 79 C. glabrata clinical isolates from different origins. Eleven of these are hyperadherent to HeLa cells under conditions in which strain BG14 is non-adherent. However, almost all of the hyperadherent isolates display the same ability to form biofilms on plastic surfaces. The majority of the hyperadherent isolates overexpress one or several of the EPA genes analyzed although each one presents a different expression pattern and there is no direct correlation between EPA gene expression and the adherence to plastic or epithelial cells. In this work we amplified and sequenced HDF1 and SIR3 of some hyperadherent clinical isolates. Our data show that the SIR3 gene of these isolates contain several polymorphisms respect to strain BG14, and some of these changes are localized at positions that flank regions required for silencing in the Sir3 protein of Saccharomyces cerevisiae.
Experimentos con microscopía óptica de párticulas Brownianas atadas a biopolímeros asociados a la diatomeas Nitzschia sp. y análisis de escala de las trayectorias de las diatomeas.
Get PDFTesis (Maestría en Nanociencias y Materiales)"En este trabajo reportamos los resultados de dos tipos de experimentos realizados con la diatomea rafidea Nitzschia sp. a nivel de células individuales por medio de microscopía óptica. En el primer experimento se capturó en video el movimiento Browniano con atadura de microesferas de poliestireno (1.26 m) donde la atadura consistió de nanofibras adhesivas asociadas a las biopelículas formadas en superficies por diatomeas de esta especie. En el segundo experimento, también por video microscopía, capturamos las trayectorias de diatomeas vivas Nitzschia sp. Para ambos experimentos se obtuvieron las series de tiempo correspondientes al movimiento Browniano con atadura y a la motilidad celular, respectivamente, y estas series fueron analizadas por el método estadístico de escala Anális de Fluctuaciones sin Tendencia (DFA, en inglés) optimizado por una transformada ondeleta. De esta manera se determinó el exponente de Hurst que caracteriza la naturaleza del movimiento Browniano de atadura y del movimiento de diatomeas vivas. Del punto de vista de fluctuaciones 1~f , encontramos que el movimiento de atadura de las microesferas es persistente, sugiriendo un movimiento Browniano de carácter fractal. Por otro lado, el movimiento celular de las diatomeas Nitzschia sp., también persistente, sugiere una motilidad celular activa con un tipo de memoria.""In this thesis, we report the results of two types of experiments we performed with the raphid type Nitzschia sp. diatom of the single cell level using optical microscopy. In the first experiment, the tethered Brownian motion of polystyrene microspheres (1.26 m) was captured in video in which the tether consisted of adhesive nanofibers associated to the biofilms formed on surfaces by diatoms of this species. In the second experiment, also done with video microscopy, we captured the trajectories of live Nitzschia sp. diatoms. For both experiments, the time series corresponding to the tethered Brownian motion and the cell motility, respectively, were obtained and analyzed with the scaling statistical method Detrended Fluctuation Analysis (DFA) optimized via a wavelet transfrom. In this way, we determined the Hurst parameter that characterizes the nature of the tethered Brownian motion and that of live diatoms. From the standpoint of 1~f fluctuations, we have found that the tethered motion of microspheres is persistent, suggesting a Brownian motion with a fractal feature. On the other hand, the cell motion of Nitzschia sp. diatoms, also persistent, suggests an active cell motility with a kind of memory.