Systematic analysis of the regulation of type three secreted effectors in Salmonella enterica serovar Typhimurium

BACKGROUND: The type III secretion system (TTSS) is an important virulence determinant of Gram-negative bacterial pathogens. It enables the injection of effector proteins into the cytosol of eukaryotic cells. These effectors ultimately manipulate the cellular functions of the infected organism. Salmonella enterica serovar Typhimurium encodes two virulence associated TTSSs encoded by the Salmonella Pathogenicity Islands (SPI) 1 and 2 that are required for the intestinal and systemic phases of the infection, respectively. However, recent studies suggest that the roles of these TTSSs are not restricted to these compartments. The regulation of TTSSs in Salmonella is very complex with several regulators operating to activate or to repress expression depending on the environmental conditions. RESULTS: We performed a systematic analysis of the regulation of type III effectors during growth in vitro. We have tested the ability of seven regulatory genes to regulate ten effector genes. Each regulator was expressed in the absence of the other six to avoid cascade effects. Our results confirm and extend the previously reported regulation of TTSS1 and TTSS2 effectors by InvF-SicA and SsrB respectively. CONCLUSION: The set of strains constructed for this study can be used to quickly and systematically study the regulation of newly identified effector genes of Salmonella enterica. The approach we have used can also be applied to study complex regulatory cascades in other bacterial species

Conocimiento de los docentes sobre la enseñanza de las Ciencias Naturales en el nivel primario

En este trabajo se presenta una revisión descriptiva de la literatura en torno a la temática de los conocimientos de los docentes sobre la enseñanza de las ciencias naturales en el nivel primario. En primer lugar, se describen las perspectivas principales que investigan sobre esta cuestión. Fundamentalmente, se distingue entre la línea del conocimiento del profesor y la del pensamiento del profesor. Se reconoció que la idea de concebir a los docentes como profesionales reflexivos que producen conocimiento sobre sus prácticas es un punto en común entre algunos autores de ambas perspectivas. Luego, se abordaron las definiciones, consensos y discusiones en torno al concepto Conocimiento Didáctico del Contenido. Por último, se focalizó en los estudios empíricos que abordan este último tópico entre los docentes del área de ciencias naturales en ejercicio del nivel primario. Si bien se evidenció la vigencia del concepto, aparece una falta de consenso en su definición; y, por otro lado, se observó la incorporación de la dimensión afectiva a los estudios.In this paper, a descriptive review of the literature on the topic of teachers' knowledge about science teaching at the primary level is presented. To this end, first, the main perspectives investigating this question were described. Mainly, a distinction was made between the "teacher's knowledge" and "teacher's thought" perspectives. We found that the conception of teachers as reflective professionals who produce knowledge about their practices is a common point among some authors of both perspectives. Then, the definitions, consensus and discussions that exist around the concept of Pedagogical Content Knowledge were addressed. Finally, this study focused on empirical researches that study the in-service elementary science teachers‟ Pedagogical Content Knowledge. The validity of the concept, the lack of consensus in its definition and the incorporation of the affective component to the studies were evidenced.Fil: Dyszel, Facundo. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Centro de Investigación y Apoyo a la Educación Científica; ArgentinaFil: Lorenzo, Maria Gabriela. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Centro de Investigación y Apoyo a la Educación Científica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentin

Experimentos en clases de ciencias: transacciones de significado en un grupo de trabajo colaborativo

En este artículo estudiamos cómo se movilizó el sentido para proponer un experimento que dio inicio a una secuencia didáctica sobre la luz. Ésta fue elaborada en un grupo de trabajo donde colaboraron docentes con investigadoras y fue implementada en diferentes aulas de primaria de un programa socioeducativo de Buenos Aires. Interesa explorar la potencialidad de esta modalidad colaborativa para propiciar la construcción de conocimiento didáctico. Se trata de un estudio de caso donde analizamos las interacciones entre las diferentes posturas de los integrantes cuando codiseñaron, implementaron y analizaron la secuencia. Identificamos que, al inicio, las discusiones del grupo estuvieron enfocadas en aspectos materiales de la planificación, pero, luego, la reflexión compartida sobre las escenas de aula posibilitó repensar las intervenciones docentes, las ideas de los alumnos y la evaluación de alternativas sobre cómo convocarlos, lo que motivó modificaciones en nuevas implementaciones y redefiniciones sobre los sentidos para proponer el experimento Por último, pudimos comprender algunas razones que obstaculizan la aproximación de los docentes a las producciones de la investigación académica

El sindicalismo de movimiento social : Algunas reflexiones en torno del concepto

Dos principales líneas de análisis recorrieron los estudios sindicales durante los últimos años en la Argentina. Por un lado se ha destacado una perspectiva de raíz sociológica atraída por los contornos que ha adquirido la protesta social, definiendo su objeto de estudio a partir de teorías ancladas en el concepto de movimientos sociales, tanto en su tradición europea como norteamericana. El fenómeno sindical ha sido, por otro lado, abordado desde una visión próxima a la ciencia política y específicamente en sintonía con los análisis neocorporatistas o de intermediación de intereses. Ambas líneas han revelado insuficiencias para caracterizar ciertos fenómenos sindicales en América latina y específicamente en la Argentina. El objetivo general de este trabajo es reflexionar en torno de algunas dimensiones que contribuyan a caracterizar formas de acción colectiva de raíz sindical que exceden el marco de las relaciones laborales.Facultad de Humanidades y Ciencias de la Educació

E. coli K-12 and EHEC Genes Regulated by SdiA

Background: Escherichia and Salmonella encode SdiA, a transcription factor of the LuxR family that regulates genes in response to N-acyl homoserine lactones (AHLs) produced by other species of bacteria. E. coli genes that change expression in the presence of plasmid-encoded sdiA have been identified by several labs. However, many of these genes were identified by overexpressing sdiA on a plasmid and have not been tested for a response to sdiA produced from its natural position in the chromosome or for a response to AHL. Methodology/Principal Findings: We determined that two important loci reported to respond to plasmid-based sdiA, ftsQAZ and acrAB, do not respond to sdiA expressed from its natural position in the chromosome or to AHLs. To identify genes that are regulated by chromosomal sdiA and/or AHLs, we screened 10,000 random transposon-based luciferase fusions in E. coli K-12 and a further 10,000 in E. coli O157:H7 for a response to AHL and then tested these genes for sdiAdependence. We found that genes encoding the glutamate-dependent acid resistance system are up-regulated, and fliE is down-regulated, by sdiA. Gene regulation by sdiA of E. coli is only partially dependent upon AHL. Conclusions/Significance: The genes of E. coli that respond to plasmid-based expression of sdiA are largely different than those that respond to chromosomal sdiA and/or AHL. This has significant implications for determining the true function o

A rapid and non-invasive method for authenticating the origin of pistachio samples by NIR spectroscopy and chemometrics

In this study, near-infrared spectroscopy coupled to chemometrics is used to build an analytical protocol to authenticate the origin of pistachio nuts (Pistacia vera L.), a high value-added food product. In particular, 483 samples from six different origins (Sicily, India, Iran, Syria, Turkey and U.S.A.) were analyzed by NIR spectroscopy. Spectra were recorded on half seeds cut longitudinally in reflectance mode. Spectral data were then processed by chemometrics to build classification models by SIMCA and PLS-DA. The discriminant approach resulted in classification accuracies higher than 90% for most of the classes. On the other hand, SIMCA built class-models with high sensitivity and specificities, the only exception being the two categories Turkey and Iran, whose heterogeneity resulted in a poorer specificity (anyway higher than 80%). In particular, the results obtained for the samples coming from Bronte (Sicily), the only PDO pistachio production in Europe 95.5% non-error rate in PLS-DA, 90% sensitivity and 97% specificity in SIMCA, as evaluated on the external test set are very promising from the viewpoint of the authentication of this product. In general, the results show that the coupling of NIR spectroscopy to chemometric classification techniques can be a valuable tool for tracing the origin of pistachio nuts, providing a reliable authentication in a rapid, relatively cheap and non-invasive way.Vitale, R.; Bevilacqua, M.; Bucci, R.; Magrì, A.; Magri, A.; Marini, F. (2013). A rapid and non-invasive method for authenticating the origin of pistachio samples by NIR spectroscopy and chemometrics. Chemometrics and Intelligent Laboratory Systems. 121:90-99. doi:10.1016/j.chemolab.2012.11.019S909912

Differential scanning calorimetric analysis of edible oils: comparison of thermal properties and chemical composition

The thermal profiles of 17 edible oil samples from different plant origins were examined by differential scanning calorimetry (DSC). Two other confirmatory analytical techniques, namely gas-liquid chromatography (GLC) and high-performance liquid chromatography (HPLC), were used to determine fatty acid (FA) and triacylglycerol (TAG) compositions. The FA and TAG compositions were used to complement the DSC data. Iodine value (IV) analysis was carried out to measure the degree of unsaturation in these oil samples. The DSC melting and crystallization curves of the oil samples are reported. The contrasting DSC thermal curves provide a way of distinguishing among these oil samples. Generally, the oil samples with a high degree of saturation (IV65). Each thermal curve was used to determine three DSC parameters, namely, onset temperature (T o ), offset temperature (T f ) and temperature range (difference between T o and T f ). Reproducibility of DSC curves was evaluated based on these parameters. Satisfactory reproducibility was achieved for quantitation of these DSC parameters. The results show that T o of the crystallization curve and T f of the melting curve differed significantly (P<0.01) in all oil samples. Our observations strengthen the premise that DSC is an efficient and accurate method for characterizing edible oils

SdiA, an N-Acylhomoserine Lactone Receptor, Becomes Active during the Transit of Salmonella enterica through the Gastrointestinal Tract of Turtles

encode a LuxR-type AHL receptor, SdiA, they cannot synthesize AHLs. In vitro, it is known that SdiA can detect AHLs produced by other bacterial species..We conclude that the normal gastrointestinal microbiota of most animal species do not produce AHLs of the correct type, in an appropriate location, or in sufficient quantities to activate SdiA. However, the results obtained with turtles represent the first demonstration of SdiA activity in animals

The Classification of an Unknown Protein 3H04

An unclassified protein in the Protein Data Bank, 3H04, was selected as a protein of interest. Research was performed in silico to gain key information on the structure, sequence, and homology of protein 3H04. This research was guided using the BASIL Project’s protocols on in silico research. Several databases were utilized to study protein 3H04. Based on the data gathered, unclassified protein 3H04 is an aminopeptidase that cleaves prolyl-dipeptidyl peptide bonds through alpha beta hydrolase function