Biosurfactant Production in Aerobic and Anaerobic Conditions by Different Species of the Genus Pseudomonas

In a time where surface active agents are capable of reducing the energy of the bonds between water molecules by interacting with them to reduce surface tension, it would be unwise not to be able to generate these in masses. Different Pseudomonas species were grown in MSP (minimal sulphate phosphate) media containing salts, glycerol and glucose. P. aeruginosa grown aerobically in the presence of glycerol as carbon source showed the highest emulsion percentage (81.48%), most significant decrease in surface tension (20 mN/m) and rhamnose production of 2.86 mg/mL. However, in anaerobic conditions there was no emulsion, rhamnolipid production or decrease in surface tension. The rhamnolipids were molecularly characterized using ESI-MS (electrospray ionization-mass spectrometry), P. aeruginosa CVCM 411 is able to produce mono-rhamnolipids and di-rhamnolipids, being rhamnolipid RhC10C12:1 the predominant monomer. The specific growth rate for isolates of P. aeruginosa and P. fluorescens in MSP are 0.6732 h-1 and 0.2181 h-1, respectively. In conclusion, the formation of rhamnolipids by P. aeruginosa is linked to its growth (depending on μ), and its ability to generate about 35% of the μmax, in the presence of glucose (carbon source) and glycerol (applied as pulses)

Modeling elastic and photoassisted transport in organic molecular wires: length dependence and current-voltage characteristics

Using a pi-orbital tight-binding model, we study the elastic and photoassisted transport properties of metal-molecule-metal junctions based on oligophenylenes of varying lengths. The effect of monochromatic light is modeled with an ac voltage over the contact. We first show how the low-bias transmission function can be obtained analytically, using methods previously employed for simpler chain models. In particular, the decay coefficient of the off-resonant transmission is extracted by considering both a finite-length chain and infinitely extended polyphenylene. Based on these analytical results, we discuss the length-dependence of the linear-response conductance, the thermopower, and the light-induced enhancement of the conductance in the limit of weak intensity and low frequency. In general the conductance-enhancement is calculated numerically as a function of the light frequency. Finally, we compute the current-voltage characteristics at finite dc voltages, and show that in the low-voltage regime, the effect of low-frequency light is to induce current steps with a voltage separation determined by twice the frequency. These effects are more pronounced for longer molecules. We study two different profiles for the dc and ac voltages, and it is found that the results are robust with respect to such variations. Although we concentrate here on the specific model of oligophenylenes, the results should be qualitatively similar for many other organic molecules with a large enough electronic gap.Comment: 15 pages, 11 figures, minor corrections to old versio

Epidemiología de Campylobacter spp. en granjas de pollos de engorde : prevalencia, factores de riesgo y dinámica de infección /

Departament responsable de la tesi: Departament de Sanitat i d'Anatomia AnimalLa campilobacteriosis es la zoonosis bacteriana más reportada en la Unión Europea (UE) desde hace una década. Causa pérdidas económicas significativas y problemas de salud pública en países desarrollados. La principal fuente de infección es el consumo o manipulación de carne de pollo contaminada con Campylobacter termófilos (principalmente C.jejuni y C.coli). La alta prevalencia de Campylobacter en pollos de engorde supone un elevado riesgo de contaminación de las canales de pollos a nivel de matadero, y por ende el riesgo de infección en el consumidor. Por ello, la prevención y reducción de la colonización en producción primaria (granjas de pollos de engorde) es una prioridad en la UE. Para alcanzar este objetivo es necesario conocer en profundidad la epidemiología de Campylobacter en granja. A pesar de los numerosos estudios existentes en este campo, continúa habiendo numerosos aspectos en los que es necesario profundizar, para llevar a cabo medidas que resulten efectivas. Es por ello que en el marco de esta tesis se han realizado una serie de estudios en granjas de pollos de engorde, que incluyeron: (i) la determinación del método óptimo y sensible de muestreo de las aves para la detección temprana y aislamiento de Campylobacter; (ii) el estudio de la dinámica de colonización en granja; (iii) el estudio del papel de las moscas como vector de introducción de Campylobacter en las naves de pollos. Para estudiar la dinámica de colonización en granja, se requería primero valorar el método óptimo para la detección temprana y aislamiento de Campylobacter en pollos de engorde en granja. De este modo, se compararon dos tipos de muestras: contenido cecal obtenido mediante necropsia de las aves e hisopos cloacales transportados en medio Amies con carbón. El uso de hisopos cloacales evita tener que sacrificar animales en granja para obtener las muestras, y facilita tanto el muestreo como su posterior procesado. La comparación de ambos tipos de matrices se realizó mediante el muestreo de cinco lotes de pollos de cinco granjas diferentes. No se encontraron diferencias entre ambos tipos de matrices, resultando las muestras de hisopos cloacales efectivas para los estudios longitudinales que se llevaron a cabo posteriormente. Con el fin de profundizar en el conocimiento de la dinámica de colonización de Campylobacter, se llevó a cabo un estudio longitudinal en 5 granjas de pollos de engorde durante dos años. Se analizaron un total de 63 lotes mediante muestreos semanales y las prevalencias por granja oscilaron entre 38,46% y 83,33%. Mediante la toma de muestras de calzas en las naves de pollos, que resultó ser el método más sensible para la detección (no aislamiento) de Campylobacter, se detectó Campylobacter a los 7 días de edad de los pollos. Mediante cultivo, la excreción de Campylobacter más temprana detectada fue a los 10 días. La velocidad de diseminación dentro de una nave de pollos es extremadamente rápida, pudiéndose determinar en este estudio que puede ser de tan sólo 2 días (rango 2-13 días). No se detectó Campylobacter en ninguna de las naves antes del inicio de cada nuevo lote, ni en los pollitos de un día o en el agua de bebida. Ello demuestra la importancia de los procesos de limpieza, desinfección y cambio de la yacija durante el vacío sanitario, para garantizar un inicio de crianza libre de Campylobacter y para evitar las infecciones entre lotes, en caso que un lote sea colonizado. Diversos factores ambientales suponen un mayor riesgo de infección de los lotes, como una mayor temperatura mínima en el interior o exterior de las naves, así como el tipo de ventilación (mayor riesgo cuando la ventilación es no forzada). Por el contrario, el tipo de cama o de bebedero no influyó en la colonización por Campylobacter. Dado que se ha descrito en el norte de Europa que las moscas pueden actuar como vectores de introducción de Campylobacter en las naves de pollos, se exploró si en un clima más cálido estos insectos suponían también un factor de riesgo. En el estudio realizado, en las mismas granjas donde se realizó el estudio longitudinal, demostramos que efectivamente, las moscas, y en particular la mosca común (Musca domestica) son un factor de riesgo en las granjas de pollos de engorde en España. Se aisló C. jejuni y C. coli de las moscas capturadas en el exterior de las naves, y en algún caso genotipos idénticos a los aislados de los pollos en el interior de las naves. Así mismo, las dos granjas que presentaron una mayor prevalencia de Campylobacter, fueron en las que se detectó mayor número de moscas positivas. Los datos generados en esta tesis contribuyen al conocimiento de la epidemiología de Campylobacter en granjas de pollos de engorde, y ponen de relieve la importancia de implementar unas medidas de bioseguridad estrictas en granja que eviten o reduzcan el riesgo de colonización de los pollos. No obstante, para un completo control de la bacteria, son necesarias medidas adicionales y complementarias, no disponibles actualmente, como el uso de estrategias nutricionales (prebióticos o probióticos) o vacunas.Campylobacteriosis is the most frequently reported bacterial zoonosis in the European Union (EU) for a decade. It causes significant economic losses and is of public health concern in developed countries. The main source of infection is consumption or handling of contaminated chicken meat with thermophilic Campylobacter (mainly C. jejuni and C. coli). High Campylobacter prevalence in broilers represents a high risk of contamination of chicken carcasses at slaughter and as a consequence, a high risk of consumer infection. Therefore, to prevent and to reduce the Campylobacter colonization in primary production (broiler farms) is a priority in EU. To achieve this goal it is necessary to gain insight into the epidemiology of Campylobacter in broiler farms. Despite the numerous studies in this field, there are still many gaps that request further research, in order to implement effective measures. Hence, in the framework of this thesis a number of studies in broiler farms have been carried out, which included: (i) determination of an optimum and sensitive method for sampling birds on farm, for an early detection and isolation of Campylobacter, (ii) the study of the dynamics of colonization on farm, (iii) the study of the role of flies as a vector for introduction of Campylobacter in broiler houses. To study of the dynamics of colonization on farm, it was first required to assess the optimal method for the early detection and isolation of thermophilic Campylobacter in broilers at farm level. Thus, two types of samples were compared: caecal contents obtained by necropsy and cloacal swabs transported in charcoal Amies medium. The use of cloacal swabs avoids sacrificing farm animals to get samples, and facilitates both sampling and further processing. Comparison of both types of matrices was carried out by sampling five broiler flocks from five different farms. No differences between the two types of matrices were found, with cloacal swabs being as effective as caecal samples, and therefore the former type of sample was used for the longitudinal studies. In order to deepen the understanding of the dynamics of colonization of Campylobacter, a 2-year longitudinal study was carried out in 5 broiler farms. A total of 63 flocks were analyzed by weekly sampling and farms prevalence ranged from 38,46% to 83,33%. Boot sock sampling was the most sensitive method to detect (not to isolate) Campylobacter, and allowed to detect Campylobacter as early as 7 days of chick placement. By culture, the earliest Campylobacter excretion was detected in 10 days-old chicks. The speed of Campylobacter spread within a broiler house is extremely fast and in this study we were able to determine that it can be of just 2 days (range 2-13 days). Campylobacter was not detected in any of the broiler houses before chick placement nor in one-day old chicks or in drinking water. This shows the importance of cleaning and disinfection and litter replacement during the down time period, to ensure a start of each rearing cycle free of Campylobacter and to prevent infection between consecutive batches, if one flock is colonized. Several environmental factors pose a greater risk of infection of flocks, such as a higher minimum temperature inside or outside of the broiler houses, as well as the type of ventilation (increased risk when not forced ventilation is used). On the contrary, the type of poultry litter or drinker did not influence colonization by Campylobacter. There are several studies in Northern Europe reporting that flies can act as vectors for introduction of Campylobacter in broiler houses. However, there are no data in countries with a warmer climate. Thus, we explored if in Southern Europe insects also posed a risk. The study was performed in the same farms where the longitudinal study was conducted and we demonstrated that indeed, flies and in particular housefly (Musca domestica) are a risk factor in Spanish broiler farms. C. jejuni and C.coli were isolated from flies captured outside the broiler houses and in some instances, the same genotypes to those isolated from chickens inside the broiler houses were found. Likewise, the two farms with a higher Campylobacter prevalence were those were the highest number of positive flies were detected. The data generated in this thesis contributes to a better understanding of the epidemiology of Campylobacter in broiler farms, and highlight the importance of implementing strict biosecurity measures on farm to avoid or reduce the risk of colonization of chickens. However, for a complete control of the bacteria, additional and complementary measures are needed, although they are not currently available, such as using nutritional strategies (prebiotics or probiotics) or vaccines

A systematic review of natural health product treatment for vitiligo

<p>Abstract</p> <p>Background</p> <p>Vitiligo is a hypopigmentation disorder affecting 1 to 4% of the world population. Fifty percent of cases appear before the age of 20 years old, and the disfigurement results in psychiatric morbidity in 16 to 35% of those affected.</p> <p>Methods</p> <p>Our objective was to complete a comprehensive, systematic review of the published scientific literature to identify natural health products (NHP) such as vitamins, herbs and other supplements that may have efficacy in the treatment of vitiligo. We searched eight databases including MEDLINE and EMBASE for vitiligo, leucoderma, and various NHP terms. Prospective controlled clinical human trials were identified and assessed for quality.</p> <p>Results</p> <p>Fifteen clinical trials were identified, and organized into four categories based on the NHP used for treatment. 1) L-phenylalanine monotherapy was assessed in one trial, and as an adjuvant to phototherapy in three trials. All reported beneficial effects. 2) Three clinical trials utilized different traditional Chinese medicine products. Although each traditional Chinese medicine trial reported benefit in the active groups, the quality of the trials was poor. 3) Six trials investigated the use of plants in the treatment of vitiligo, four using plants as photosensitizing agents. The studies provide weak evidence that photosensitizing plants can be effective in conjunction with phototherapy, and moderate evidence that <it>Ginkgo biloba </it>monotherapy can be useful for vitiligo. 4) Two clinical trials investigated the use of vitamins in the therapy of vitiligo. One tested oral cobalamin with folic acid, and found no significant improvement over control. Another trial combined vitamin E with phototherapy and reported significantly better repigmentation over phototherapy only. It was not possible to pool the data from any studies for meta-analytic purposes due to the wide difference in outcome measures and poor quality ofreporting.</p> <p>Conclusion</p> <p>Reports investigating the efficacy of NHPs for vitiligo exist, but are of poor methodological quality and contain significant reporting flaws. L-phenylalanine used with phototherapy, and oral <it>Ginkgo biloba </it>as monotherapy show promise and warrant further investigation.</p