Design of a millifluidic device for the evaluation of blue-light disinfection on Pseudomonas aeruginosa PA01 biofilm

Significance: For the first time to our knowledge, a millifluidic device has been designed to observe the effects of blue-light irradiation in Pseudomonas aeruginosa PA01 bacterial biofilm. Approach: A bacterial biofilm is formed under controlled flow of nutrients in microfabricated channels settled on a microscope stage. The setup is devised to apply defined irradiation and evaluate the photo-killing efficiency in situ using video-microscopy and fluorescent probes. Results: We investigated bacterial survival after delivering a precise, controlled and spatially defined blue light dose upon growing biofilm. We demonstrate in this report that the combined use of constitutive GFP and propidium iodide in a millifluidic setup enables to evidence light-induced mortality at the single cell and community level. Conclusions: Real-time monitoring of a bacterial biofilm growing in a millifluidic device after irradiation opens an avenue for a better understanding of the biofilm community response to blue-light, permitting researchers to approach photokilling efficiency of biofilm as a dynamic process

A Short–Time Scale Colloidal System Reveals Early Bacterial Adhesion Dynamics

The development of bacteria on abiotic surfaces has important public health and sanitary consequences. However, despite several decades of study of bacterial adhesion to inert surfaces, the biophysical mechanisms governing this process remain poorly understood, due, in particular, to the lack of methodologies covering the appropriate time scale. Using micrometric colloidal surface particles and flow cytometry analysis, we developed a rapid multiparametric approach to studying early events in adhesion of the bacterium Escherichia coli. This approach simultaneously describes the kinetics and amplitude of early steps in adhesion, changes in physicochemical surface properties within the first few seconds of adhesion, and the self-association state of attached and free-floating cells. Examination of the role of three well-characterized E. coli surface adhesion factors upon attachment to colloidal surfaces—curli fimbriae, F-conjugative pilus, and Ag43 adhesin—showed clear-cut differences in the very initial phases of surface colonization for cell-bearing surface structures, all known to promote biofilm development. Our multiparametric analysis revealed a correlation in the adhesion phase with cell-to-cell aggregation properties and demonstrated that this phenomenon amplified surface colonization once initial cell-surface attachment was achieved. Monitoring of real-time physico-chemical particle surface properties showed that surface-active molecules of bacterial origin quickly modified surface properties, providing new insight into the intricate relations connecting abiotic surface physicochemical properties and bacterial adhesion. Hence, the biophysical analytical method described here provides a new and relevant approach to quantitatively and kinetically investigating bacterial adhesion and biofilm development

INVESTIGACIÓN Y DESARROLLO DE TRES PRODUCTOS DEL JABONCILLO (Sapindus saponaria L.) COMO BASE PARA SU INDUSTRIALIZACIÓN

This research included the chemical and phytochemical studies and the industrial scaling in pilot plant of three products of Sapindus saponaria, commonly known as jaboncillo, Michu. This work is part of an interdisciplinary research project aimed at the exploitation and commercialization of its harvested products: oil, gum, and triterpenoidal sapogenins. These three products were obtained through physical and chemical processes both in laboratory (phase 1) and in the industrial scaling stage (phase 2). During the laboratory stage different methods of extraction and purification were studied and assessed, along with the corresponding methods of chemical analysis for the three origins (Palmira, Valle; Viotá, Cundinamarca, and Santa María, Huila). Based on laboratory studies, extraction and purification processes were designed in a pilot plant supplied by the quinacol ltda. company, whose business is the production, research and development of products for the phytopharmaceutical industry. Developed products were characterized by methods of instrumental analysis of nuclear magnetic resonance (1 H nmr and 13c), flame ionization detector gas chromatography (gc), infrared spectroscopy (ir) and specific chemical analysis techniques designed for these products. The mature fruit of Santa María presented increased performance of oil and rubber; as well as the green fruit of Viotá, in a substance called Ss1, possibly hederagenina. Of the products obtained in the pilot phase, oil presented a high percentage of unsaturated fatty acids and rubber showed a high thickening capacity in aqueous solutions. Oil and rubber could be marketed from this species' fruit, because its composition and characteristics, as well as its performance, meets the main parameters of marketing, for which studies on industrial perfectibility are needed.Esta investigación comprendió el estudio químico, fitoquímico y el escalado industrial, en planta piloto, de tres productos de la especie Sapindus saponaria conocida comúnmente en Colombia como jaboncillo, Michu. Este trabajo hace parte de un proyecto interdisciplinar encaminado a aprovechar y comercializar sus productos derivados: aceite, goma y sapogeninas triterpenoidales. La obtención de estos tres productos se llevó a cabo mediante procesos físicos y químicos tanto en laboratorio (Fase 1), como en la etapa de escalado industrial (Fase 2). En la etapa de laboratorio se estudiaron y evaluaron diferentes métodos de extracción y purificación, al igual que los correspondientes métodos de análisis químico para tres procedencias (Palmira, Valle; Viotá, Cundinamarca, y Santa María, Huila). Con base en los estudios de laboratorio sediseñaron los procesos de extracción y purificaciónen planta piloto suministrada por la empresa quinacol ltda., cuya razón social es la producción, investigación y desarrollo de productos para la industria fitofarmacéutica. Los productos desarrollados fueron caracterizados por métodos de análisis instrumental de resonancia magnética nuclear (rmn de 1H y 13C), cromatografía de gases con detector de ionización de llama (cg), espectroscopia infrarroja (ir) y técnic as de análisis químico específicas para estos productos

Extracellular Bacterial Pathogen Induces Host Cell Surface Reorganization to Resist Shear Stress

Bacterial infections targeting the bloodstream lead to a wide array of devastating diseases such as septic shock and meningitis. To study this crucial type of infection, its specific environment needs to be taken into account, in particular the mechanical forces generated by the blood flow. In a previous study using Neisseria meningitidis as a model, we observed that bacterial microcolonies forming on the endothelial cell surface in the vessel lumen are remarkably resistant to mechanical stress. The present study aims to identify the molecular basis of this resistance. N. meningitidis forms aggregates independently of host cells, yet we demonstrate here that cohesive forces involved in these bacterial aggregates are not sufficient to explain the stability of colonies on cell surfaces. Results imply that host cell attributes enhance microcolony cohesion. Microcolonies on the cell surface induce a cellular response consisting of numerous cellular protrusions similar to filopodia that come in close contact with all the bacteria in the microcolony. Consistent with a role of this cellular response, host cell lipid microdomain disruption simultaneously inhibited this response and rendered microcolonies sensitive to blood flow–generated drag forces. We then identified, by a genetic approach, the type IV pili component PilV as a triggering factor of plasma membrane reorganization, and consistently found that microcolonies formed by a pilV mutant are highly sensitive to shear stress. Our study shows that bacteria manipulate host cell functions to reorganize the host cell surface to form filopodia-like structures that enhance the cohesion of the microcolonies and therefore blood vessel colonization under the harsh conditions of the bloodstream

Análisis estructural y morfológico de películas de nitruro de aluminio obtenidas por deposición de láser pulsado

This paper gives the preliminary results about aluminum nitride (AlN) nanoestructured films deposited by pulsed laser deposition (PLD) technique, by using laser Nd:YAG (λ=1064), which hit a target of high purity aluminum (4N) in a nitrogen atmosphere. We used glass slide, Si 3 N4 (100) and Si (100) as substrates. The deposition time was 15 minutes at laser fluence 7 J/cm2 and room temperature. The thicknesses of thin films were 50 nm measured with a profilometer. The influence of nitrogen on thin films was studied by changing room gas pressure between 3 and 4 mTorr. Also we have studied the influence of substrate on morphological properties of AlN thin films. The film nanostructure was determined by scanning electron microscopy (SEM), atomic force microscopy (AFM) –the chemical composition– using the technique of energy dispersive X-ray (EDX). The crystal structure was examined with X-Ray Diffraction (XRD) to a 4 mTorr film on a Si3 N4 (100) substrate giving a polycrystalline structure with reflections of planes (002), linked to the wurtzite-like structure of AlN.En este trabajo, se presentan los resultados preliminares de películas nanoestructuradas de nitruro de aluminio (AlN), que fueron depositadas con el método de deposición por láser pulsado (PLD). Al efecto, se utilizó un láser Nd:YAG (¿=1064nm), que impacto un blanco de aluminio de alta pureza (4N), en una atmósfera de nitrógeno. Se utilizaron como sustratos portaobjetos de vidrio, Si3N4 (100) y Si (100). El tiempo de deposición fue de 15 minutos a una fluencia del láser 7 J/cm2 y a temperatura ambiente. El espesor de las películas fue de 50 nm medido con un perfilómetro. Para estudiar la influencia del nitrógeno en las películas delgadas de AlN, se varió la presión del gas ambiente entre (3 y 4) mTorr. Igualmente se estudió la influencia del sustrato en las propiedades morfológicas de las películas delgadas de AlN. La nanoestructura de las películas se determinó mediante microscopia electrónica de barrido (SEM), y microscopia de fuerza atómica (AFM); la composición química, utilizando la técnica de espectroscopía de rayos X por dispersión de energía (EDX). La estructura cristalina fue estudiada con difracción de rayos X (DRX), para la película de 4 mTorr sobre un sustrato de Si3N4 (100), y se encontró una estructura policristalina con reflexiones de los planos (002), asociados a la estructura tipo wurtzita del AlN

Administrando redes en el servidor zentyal 6.2 solucionado necesidades específicas

El presente informe trae a colación la implementación de un servidor con el sistema operativo Zentyal en versión 6.2 cuyo objetivo permite de manera centralizada la administración de los servicios de un servidor soportados en Debian, con una gestión de controlar la configuración de manera correcta dependiendo de los requerimientos de usuarios, teniendo la capacidad, calidad y solidez de Linux para este tipo de proyectos encaminados en el control de los módulos o programas Zentyal 6.2 donde se logró una seguridad robusta en las redes y se protegió a los usuarios de posibles vulnerabilidades y ataques del sistema siendo, así unas oportunidad de tener un ahorro, por ende buenas ganancias en una corporación donde se implementes estas herramientas.This report brings up the implementation of a server with the Zentyal operating system in version 6.2 whose objective allows centralized administration of the services of a server supported in Debian, with a management to control the configuration correctly depending on the user requirements, taking into account the capacity, quality and robustness of Linux for this type of projects aimed at controlling Zentyal 6.2 modules or programs where robust security was achieved in the networks and users were protected from possible vulnerabilities and attacks of the system being, thus, opportunities to have savings, therefore good profits in a corporation where these tools are implemented

Un nouveau type de matière active explique la formation d’agrégats bactériens et leur impact sur l’infection à méningocoque

International audienc

T-Cell Artificial Focal Triggering Tools: Linking Surface Interactions with Cell Response

T-cell activation is a key event in the immune system, involving the interaction of several receptor ligand pairs in a complex intercellular contact that forms between T-cell and antigen-presenting cells. Molecular components implicated in contact formation have been identified, but the mechanism of activation and the link between molecular interactions and cell response remain poorly understood due to the complexity and dynamics exhibited by whole cell-cell conjugates. Here we demonstrate that simplified model colloids grafted so as to target appropriate cell receptors can be efficiently used to explore the relationship of receptor engagement to the T-cell response. Using immortalized Jurkat T cells, we monitored both binding and activation events, as seen by changes in the intracellular calcium concentration. Our experimental strategy used flow cytometry analysis to follow the short time scale cell response in populations of thousands of cells. We targeted both T-cell receptor CD3 (TCR/CD3) and leukocyte-function-associated antigen (LFA-1) alone or in combination. We showed that specific engagement of TCR/CD3 with a single particle induced a transient calcium signal, confirming previous results and validating our approach. By decreasing anti-CD3 particle density, we showed that contact nucleation was the most crucial and determining step in the cell-particle interaction under dynamic conditions, due to shear stress produced by hydrodynamic flow. Introduction of LFA-1 adhesion molecule ligands at the surface of the particle overcame this limitation and elucidated the low TCR/CD3 ligand density regime. Despite their simplicity, model colloids induced relevant biological responses which consistently echoed whole cell behavior. We thus concluded that this biophysical approach provides useful tools for investigating initial events in T-cell activation, and should enable the design of intelligent artificial systems for adoptive immunotherapy

Force Generation upon T Cell Receptor Engagement

T cells are major players of adaptive immune response in mammals. Recognition of an antigenic peptide in association with the major histocompatibility complex at the surface of an antigen presenting cell (APC) is a specific and sensitive process whose mechanism is not fully understood. The potential contribution of mechanical forces in the T cell activation process is increasingly debated, although these forces are scarcely defined and hold only limited experimental evidence. In this work, we have implemented a biomembrane force probe (BFP) setup and a model APC to explore the nature and the characteristics of the mechanical forces potentially generated upon engagement of the T cell receptor (TCR) and/or lymphocyte function-associated antigen-1 (LFA-1). We show that upon contact with a model APC coated with antibodies towards TCR-CD3, after a short latency, the T cell developed a timed sequence of pushing and pulling forces against its target. These processes were defined by their initial constant growth velocity and loading rate (force increase per unit of time). LFA-1 engagement together with TCR-CD3 reduced the growing speed during the pushing phase without triggering the same mechanical behavior when engaged alone. Intracellular Ca2+ concentration ([Ca2+]i) was monitored simultaneously to verify the cell commitment in the activation process. [Ca2+]i increased a few tens of seconds after the beginning of the pushing phase although no strong correlation appeared between the two events. The pushing phase was driven by actin polymerization. Tuning the BFP mechanical properties, we could show that the loading rate during the pulling phase increased with the target stiffness. This indicated that a mechanosensing mechanism is implemented in the early steps of the activation process. We provide here the first quantified description of force generation sequence upon local bidimensional engagement of TCR-CD3 and discuss its potential role in a T cell mechanically-regulated activation process

Salud de los trabajadores

Actividad física y su relación con los factores de riesgo cardiovascular de carteros chilenosAnálisis de resultados: riesgos psicosociales en el trabajo Suceso-Istas 21 en Cesfam QuellónAusentismo laboral por enfermedades oftalmológicas, Chile 2009Brote de diarreas por norovirus, posterremoto-tsunami, Constitución, Región del MauleCalidad de vida en profesionales de la salud pública chilenaCaracterización del reposo laboral en personal del SSMN durante el primer semestre de 2010Concentración de nicotina en pelo en trabajadores no fumadores expuestos a humo de tabaco ambientalCondiciones de trabajo y bienestar/malestar docente en profesores de enseñanza media de SantiagoDisfunción auditiva inducida por exposición a xilenoErgonomía aplicada al estudio del síndrome de dolor lumbar en el trabajoEstimación de la frecuencia de factores de riesgo cardiovascular en trabajadores de una empresa mineraExposición a plaguicidas inhibidores de la acetilcolinesterasa en Colombia, 2006-2009Factores de riesgo y daños de salud en conductores de una empresa peruana de transporte terrestre, 2009Las consecuencias de la cultura en salud y seguridad ocupacional en una empresa mineraPercepción de cambios en la práctica médica y estrategias de afrontamientoPercepción de la calidad de vida en la Universidad del BiobíoPesos máximos aceptables para tareas de levantamiento manual de carga en población laboral femeninaRiesgo coronario en trabajadores mineros según la función de Framingham adaptada para la población chilenaTrastornos emocionales y riesgo cardiovascular en trabajadores de la salu