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Darsonval M.,CNRS Food Processing and Microbiology Laboratory | Msadek T.,Institute Pasteur Paris | Msadek T.,French National Center for Scientific Research | Alexandre H.,CNRS Food Processing and Microbiology Laboratory | And 2 more authors.
Applied and Environmental Microbiology

Oenococcus oeni is a wine-associated lactic acid bacterium mostly responsible for malolactic fermentation in wine. In wine, O. oeni grows in an environment hostile to bacterial growth (low pH, low temperature, and ethanol) that induces stress response mechanisms. To survive, O. oeni is known to set up transitional stress response mechanisms through the synthesis of heat stress proteins (HSPs) encoded by the hsp genes, notably a unique small HSP named Lo18. Despite the availability of the genome sequence, characterization of O. oeni genes is limited, and little is known about the in vivo role of Lo18. Due to the lack of genetic tools for O. oeni, an efficient expression vector in O. oeni is still lacking, and deletion or inactivation of the hsp18 gene is not presently practicable. As an alternative approach, with the goal of understanding the biological function of the O. oeni hsp18 gene in vivo, we have developed an expression vector to produce antisense RNA targeting of hsp18 mRNA. Recombinant strains were exposed to multiple stresses inducing hsp18 gene expression: Heat shock and acid shock. We showed that antisense attenuation of hsp18 affects O. oeni survival under stress conditions. These results confirm the involvement of Lo18 in heat and acid tolerance of O. oeni. Results of anisotropy experiments also confirm a membrane-protective role for Lo18, as previous observations had already suggested. This study describes a new, efficient tool to demonstrate the use of antisense technology for modulating gene expression in O. oeni. © 2015, American Society for Microbiology. Source

Ryona I.,Cornell University | Leclerc S.,Institute National Superieur des science Agronomiques | Sacks G.L.,Cornell University
Journal of Agricultural and Food Chemistry

Environmental factors affecting degradation of 3-isobutyl-2-methoxypyrazine (IBMP, "green pepper aroma") in wine grapes (V. vinifera) are widely studied, but the degradation pathway is not defined. We hypothesized that IBMP is demethylated to 3-isobutyl-2-hydroxypyrazine (IBHP) during fruit maturation effectively reversing the final putative step of IBMP biosynthesis. A quantification method for IBHP was developed using solid-phase extraction coupled to one- or two-dimensional gas chromatography-mass spectrometry with a recovery of ca. 80%. IBMP and IBHP in bell peppers (Capsicum annuum) and V. vinifera (cv. Cabernet Franc , Riesling , Pinot noir ) were then measured at different maturities. IBMP and IBHP were inversely correlated in both bell peppers (R2 = 0.958) and Cabernet Franc grapes (R2 = 0.998) over a range of maturities. In bell peppers, we observed a significant decline in IBMP (125 to 15 ng/mL) and increase in IBHP (undetectable to 42 ng/mL) during ripening. In grapes, all cultivars had comparable IBHP concentrations preveraison (64 to 88 pg/mL) but differed in IBHP concentration by 2 orders of magnitude at the final sampling point (undetectable to 235 pg/mL). Higher preveraison IBMP was correlated with higher final IBHP across the three grape cultivars, with the order Cabernet Franc > Riesling > Pinot noir for both IBMP and IBHP. Acid hydrolysis resulted in a significant increase (33%) in IBHP in Cabernet Franc, indicating that IBHP exists partially in a bound form in grapes. © 2010 American Chemical Society. Source

Hijazi B.,Belgium Institute for Agricultural and Fisheries Research | Hijazi B.,Institute National Superieur des science Agronomiques | Hijazi B.,CNRS Laboratory for the Study of Learning and Development | Hijazi B.,Ghent University | And 7 more authors.
Sensors (Switzerland)

A 3D imaging technique using a high speed binocular stereovision system was developed in combination with corresponding image processing algorithms for accurate determination of the parameters of particles leaving the spinning disks of centrifugal fertilizer spreaders. Validation of the stereo-matching algorithm using a virtual 3D stereovision simulator indicated an error of less than 2 pixels for 90% of the particles. The setup was validated using the cylindrical spread pattern of an experimental spreader. A 2D correlation coefficient of 90% and a Relative Error of 27% was found between the experimental results and the (simulated) spread pattern obtained with the developed setup. In combination with a ballistic flight model, the developed image acquisition and processing algorithms can enable fast determination and evaluation of the spread pattern which can be used as a tool for spreader design and precise machine calibration. © 2014 by the authors; licensee MDPI, Basel, Switzerland. Source

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