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SigmaB (σB) Regulates IS256-Mediated Staphylococcus aureus Biofilm Phenotypic Variation
No full textBiofilm formation in Staphylococcus aureus is subject to phase variation, and biofilm-negative derivatives emerge sporadically from a biofilm-positive bacterial population. To date, the only known mechanism for generating biofilm phenotypic variation in staphylococci is the reversible insertion/excision of IS256 in biofilm-essential genes. In this study, we present evidence suggesting that the absence of the sigma(B) transcription factor dramatically increases the rate of switching to the biofilm-negative phenotype in the clinical isolate S. aureus 15981, under both steady-state and flow conditions. The phenotypic switching correlates with a dramatic increase in the number of IS256 copies in the chromosomes of biofilm-negative variants, as well as with an augmented IS256 insertion frequency into the icaC and the sarA genes. IS256-mediated biofilm switching is reversible, and biofilm-positive variants could emerge from biofilm-negative sigma(B) mutants. Analysis of the chromosomal insertion frequency using a recombinant IS256 element tagged with an erythromycin marker showed an almost three-times-higher transposition frequency in a Delta sigma(B) strain. However, regulation of IS256 activity by sigma(B) appears to be indirect, since transposase transcription is not affected in the absence of sigma(B) and IS256 activity is inhibited to wild-type levels in a Delta sigma(B) strain under NaCl stress. Overall, our results identify a new role for sigma(B) as a negative regulator of insertion sequence transposition and support the idea that deregulation of IS256 activity abrogates biofilm formation capacity in S. aureus
Calibration transfer between NIR diode array and FT-NIR spectrophotometers for measuring the soluble solids contents of apple
No full textPrediction models of soluble solids contents of fruit obtained with a specific near-infrared spectrophotometer cannot be directly transferred to another spectrophotometer. In this research, a piecewise direct standardization method has been used for this task. As a result, a calibration model for soluble solids contents of apple developed on a Fourier transform based spectrophotometer has been successfully transferred to a diode array (DA) spectrophotometer. The standardization procedure was performed on a data set of 477 Jonagored apples and root mean squared error of prediction of 0.85 degrees Brix was obtained. Additionally, the necessity of calibration transfer procedures between two DA spectrophotometers of the same type and model has also been found. (C) 2007 Elsevier B.V. All fights reserved
Spinosad bait treatments as alternative to malathion to control the Mediterranean fruit fly Ceratitis capitata (Diptera : Tephritidae) in the Mediterranean Basin
Get PDFCurrent Ceratitis capitata (Wiedemann) control in Spain is based primarily on applications of organophosphate insecticides, especially malathion, mixed with protein baits. In Spain, one of the current research lines is focused on finding more environmentally friendly insecticides. One such alternative is the insecticide spinosad. We compared two formulations and various concentrations of spinosad bait treatments (10% Spintor Cebo(R)) and 0.05, 0.1, and 0.15% Spintor 480 SC(R)+0.5% Nu-lure) under laboratory conditions and found all treatments to be effective in causing high mortality of C. capitata adults within 6 days of exposure to 0-, 3-, or 6-day-old residues. Field trials demonstrated that 5% Spintor Cebo(R), 0.1% Spintor 480 SC(R)+0.5% Nu-lure, and 0.5% Malafin 50(R)+0.5% Nu-lure reduced C. capitata adults similarly and protected fruit from C capitata damage to a similar extent. Both spinosad treatments will be promising as a replacement for malathion in bait sprays. (C) Pesticide Science Society of Japan
Adecuación del tratamiento de desverdización para minimizar alteraciones fisiológicas durante la comercialización de mandarinas
Get PDFLas mandarinas tempranas alcanzan los valores mínimos exigidos de porcentaje de zumo e índice de madurez antes que la coloración comercial de la piel, por lo que, en buena parte, son sometidas a tratamiento de desverdización. En la actualidad se utiliza el sistema de flujo continuo intermitente con 2-5 ppm de etileno, humedad relativa superior al 90%, temperatura de 20-22ºC, concentración de CO2 menor del 0,2% y de O2 superior al 20%. Siendo éstas las condiciones óptimas del tratamiento de desverdización con etileno, es inevitable que si la duración del mismo se prolonga excesivamente puedan aparecer alteraciones fisiológicas relacionadas con la senescencia durante la posterior comercialización, especialmente el ennegrecimiento y caída de cálices. En este trabajo se analiza la respuesta de cambio de color y la sensibilidad a las alteraciones fisiológicas de las variedades de mayor interés comercial, incluidas las nuevas mutaciones extratempranas de clementina Oronules de atractivo color naranja-rojizo intenso (Basol, Prenules, Clemenrubi, Cultifort y Orogros). La desverdización en las mismas condiciones ambientales antes señaladas, pero sin adición de etileno exógeno, resulta en una disminución de la velocidad de cambio de color pero también en una menor incidencia de alteraciones fisiológicas. Teniendo en cuenta estos factores hemos establecido tratamientos generales de desverdización en función del índice de color inicial y el destino final a la U.E. o a países de ultramar, procurando siempre minimizar las alteraciones fisiológicas al final de la comercialización. Cuando el índice de color (IC=1000.a/L.b) en la recolección es superior a –5, los frutos pueden ser desverdizados sin etileno, llegando a destino con adecuado color comercial. También se exponen en este trabajo los resultados positivos obtenidos con la aplicación postcosecha, previa a la desverdización con etileno, de diversas auxinas de síntesis. La aplicación de formulaciones del ácido 2,4 diclorofenoxiacético y del 3,5,6 tricloro-2 piridil-oxiacético, en inmersión a concentraciones de 10 ppm logró, en algunas variedades, una significativa reducción de la caída y ennegrecimiento del cáliz sin afectar negativamente al cambio de color ni a otros parámetros y atributos de calidad evaluados
Desarrollo de un sensor de aromas para la evaluación de la calidad de productos agroalimentarios
Get PDFEl Centro de Agroingeniería del Instituto Valenciano de Investigaciones Agrarias (IVIA) ha trabajado durante los últimos siete años en el desarrollo de un sensor de aromas basado en sensores de gases semiconductores. En la actualidad, este tipo de sensores se utilizan en muchos sectores, entre ellos, el sector agroalimentario. El sensor de aromas ha demostrado su capacidad de estimar la calidad de dos productos de naturaleza muy diferentes: aceite de oliva y mosto destinado a vinificación. Por un lado, hoy en día el control de calidad para el aceite de oliva se realiza bien mediante paneles sensoriales, bien mediante análisis químicos. El coste económico es bastante elevado para los dos casos. Los sensores de aromas pueden resolver, parcialmente, este problema. El sensor de aromas permite detectar tres atributos negativos y establecer su intensidad: el rancio, el avinado y el atrojado. Por otro lado, actualmente apenas existen controles de calidad de las uvas en las bodegas a pesar de la gran influencia que representa su estado en la calidad final del vino. El sensor de aromas supone la posibilidad de incorporar un nuevo sensor a la evaluación de la calidad del mosto, ya que es capaz de predecir de forma rápida el contenido en ácido glucónico procedente de la acción de hongos (Botrytis cinerea) sobre la uva en el campo. El bajo coste de los sensores que lo componen y la rápida velocidad de respuesta del sensor de aromas si lo comparamos con otros métodos, permiten hacer pensar en su viabilidad para
integrarlo en el proceso productivo de las bodegas. Los resultados obtenidos con el sensor de aromas permiten asegurar que el Centro de AgroIngeniería del IVIA ha desarrollado dos métodos de medida reproducibles que es un logro que pocos grupos de investigación a nivel mundial han conseguido
Light acclimation in rose (Rosa hybrida cv. Grand Gala) leaves after pruning: Effects on chlorophyll a fluorescence, nitrate reductase, ammonium and carbohydrates
No full textChanges in light intensity have a particular effect on the photosynthetic apparatus. Most of the studies on light acclimation in higher plants have focused on the effects of fixed light intensity. Few works deal on sudden changes in light intensity due to pruning for long periods of time. Pruning the bent shoots in roses (cv. Grand Gala) can modify the light interception in internal leaves and change their photosynthetic reactions. Before pruning, internal leaves were acclimated to low light intensity and after pruning, internal and external leaves received the same light intensity. The aim of this work was to find out how the photosynthetic light reaction, measured by chlorophyll (Chl) a fluorescence in internal and external leaves of arched shoot could be modulated by light changes. Other parameters described as light dependent were also measured: nitrate reductase (NR) activity, NH4+, sucrose and starch levels. Internal and external leaves in rose have shown a high plasticity, rapid and dynamical acclimation, in response to changes in incident sunlight produced by pruning, that can be explained by Chl a fluorescence parameters. The modified NR activity, NH4+,, sucrose and starch levels were difficult to associated with light intensity changes, and their modulation could be the response to long-time light acclimation
Evaluación del riesgo ambiental del cultivo en campo de ciruelos europeos transgénicos sensibles y resistentes a Plum pox virus
Get PDFEl impacto ambiental de la liberación al campo de ciruelos europeos (Prunus domestica L.) transgénicos portadores del gen de la proteína de la cápsida (CP) de Plum pox virus (PPV) se ha evaluado durante un periodo de ocho años, en una finca experimental de Liria, Valencia, y los resultados obtenidos se
revisan y discuten en este trabajo. La variabilidad molecular de poblaciones de PPV que infectan ciruelos transgénicos se comparó con la de poblaciones de PPV que infectan ciruelos no transgénicos, así
como el número y las especies de pulgones (vectores de transmisión del virus) y otros artrópodos que
visitaron los dos tipos de árboles del campo experimental. Además, se estudió la posibilidad de que en
los ciruelos transgénicos emergieran virus recombinantes (entre el ARNm del transgén y el ARN de un
virus infectivo) con propiedades biológicas alteradas y potencialmente peligrosas. Para los ensayos se
utilizaron cinco líneas transgénicas de ciruelo europeo (la línea C5 ‘HoneySweet’ resistente a PPV y las
líneas C4, C6, PT6 y PT23, susceptibles a PPV) y ciruelos europeos y japoneses (P. salicina Lind) no transgénicos. No se detectaron diferencias entre la variabilidad de las poblaciones de PPV presentes en
ciruelos transgénicos y no transgénicos ni en el número y especies de pulgones y otros artrópodos que
visitaron ciruelos transgénicos y convencionales. Tampoco se detectaron virus recombinantes viables
en las plantas transgénicas después de ocho años de exposición de las mismas a la infección natural
por PPV. Los datos indican que el cultivo en campo de ciruelos europeos transgénicos en condiciones
mediterráneas no supone ningún riesgo ambiental, en términos de los parámetros estudiados, más
allá del ocasionado por el cultivo de ciruelos convencionales
Pre-commercial sorting line for peaches firmness assessment
No full textIn the fruit and vegetable sector, the demand of quality has become an important demand for consumers. Whereas first requirement sheets mainly dealt with the visual aspect, currently there is an increasing interest in other quality features, such as maturity. Maturity can be assessed by measuring firmness and sugar content. Through contract CRAFT-1999-70106, funded by the European Union, the Instituto Valenciano de Investigaciones Agrarias (IVIA) has designed a firmness sensor capable of classifying peaches in three categories: very firm, firm and not firm. This paper describes the developed sensor which is based on the analysis of fruit impact on a load cell (curve of force vs time) and its integration in a pre-commercial sorting line. The repeatability tests have demonstrated that the firmness sensor can work appropriately at,a speed of 8 fruits s(-1) and the sensor is able to classify peaches according to their firmness with 80% repeatability. (c) 2007 Elsevier Ltd. All rights reserved
Effect of different extenders and washing of seminal plasma on buck semen storage at 5 degrees C
No full textIn this research, we compared the effect of three extenders for buck semen conservation; skimmed Milk (M), sodium Citrate (C) and a Tris-based diluent (T) and the washing of semen (removal of seminal plasma) on the in vitro viability of Murciano-Granadina goat spermatozoa stored at 5 degrees C for 72 h. Motility, acrosome integrity and HOS test were evaluated to assess in vitro sperm viability. Milk diluent provided higher in vitro viability of spermatozoa than semen diluted in T during storage at 5 degrees C. Motility in semen diluted in citrate and milk extenders was improved when semen was washed previously. In milk extender, membrane integrity (HOST) was also improved with the washing of semen. In conclusion, removal of seminal plasma could be necessary for successful chilled conservation of buck semen at 5 degrees C when M or C based diluents is used. Milk media and washing of seminal plasma appears to be a successful method to prolong the viability of Murciano-Granadina goat semen stored at 5 degrees C. The latest results must be confirmed in field assays
Efficient production of transgenic citrus plants using isopentenyl transferase positive selection and removal of the marker gene by site-specific recombination
No full textThe presence of marker genes conferring antibiotic resistance in transgenic plants represents a serious obstacle for their public acceptance and future commercialization. In citrus, selection using the selectable marker gene nptII, that confers resistance to the antibiotic kanamycin, is in general very effective. An attractive alternative is offered by the MAT system (Multi-Auto-Transformation), which combines the ipt gene for positive selection with the recombinase system R/RS for removal of marker genes from transgenic cells after transformation. Transformation with a MAT vector has been attempted in two citrus genotypes, Pineapple sweet orange (Citrus sinensis L. Osb.) and Carrizo citrange (C. sinensis L. Osb. x Poncirus trifoliata L. Raf.). Results indicated that the IPT phenotype was clearly distinguishable in sweet orange but not in citrange, and that excision was not always efficient and precise. Nevertheless, the easy visual detection of the IPT phenotype combined with the higher transformation efficiency achieved in sweet orange using this system open interesting perspectives for the generation of marker-free transgenic citrus plants