Étude bactériologique comparative des fromages frais marocains commercialisés (Mahlabats) et des fromages fabriqués au laboratoire

Vingt échantillons de fromage frais traditionnel marocain (jben) fabriqué à partir du lait cru, prélevés de cinq laiteries traditionnelles (Mahlabats) de la ville de Kenitra ;ont été soumis à des analyses microbiologiques, à fin de mettre en évidence leur qualité bactériologique et de les comparer avec le fromage contrôlé préparé au laboratoire . Les résultats obtenus montrent que le pH moyen de ces échantillons commercialisés est de 4,25 et l'acidité moyenne est de 87,4D°. Ces valeurs sont respectivement de l’ordre de 4,18 et 83D au niveau des fromages contrôlés (10 échantillons). La charge microbienne aérobie totale est en moyenne de 1,14 107UFC/g, alors que pour les fromages contrôlés les valeurs oscillent entre 3 et 9.106UFC/g. La flore d'origine fécale (coliformes totaux et fécaux) est plus importante dans les fromages commercialisés et en moyenne respectives de 1,04.103 UFC/g et 5,7.104 UFC/g. Les fromages contrôlés sont dépourvus de toute contamination d’origine fécale. Nous avons souligné également l’absence totale des Staphylocoques, Salmonelles et clolésstriduims dans tous les échantillons analysés.Mots-clés : fromage frais, qualité bactériologique

Effet du traitement salin sur la croissance du blé dur (Triticum durum Desf.)

L'effet du traitement salin sur la croissance est étudié chez deux cultivars du blé dur ( Triticum durum Desf.) à sensibilités différentes vis-à-vis du stress salin et cultivés au Maroc: "Kyperounda" et "Karim". Les résultats obtenus montrent qu'avec l'avancement du cycle végétatif, la croissance (mesurée par la matière sèche) est de plus en plus affectée par le traitement salin et ceci d'une manière plus marquée chez la variété "Kyperounda". Les équations de régression établies (reliant)a matière sèche et la conductivité électrique de la solution d'arrosage) permettent de prédire l'effet de la salinité sur différents stades de la croissance et de déterminer des indices caractéristiques de la variété: seuil "S", taux de réduction "t", concentration provoquant 20% de réduction (C20) et concentration provoquant 50% de réduction de la croissance (C 50). Ces deux derniers paramètres sont respectivement égaux à 20/t + S et 50/t + S. D'autre part, la comparaison des différents stades montre que la germination reste peu sensible alors qu'à la fin de la montaison par exemple des chutes de la croissance de 20% et 50% sont provoqués par 3,06 gll et 6,11 gll pour "Karim" et 2,47 gll et 4,87 gll pour "Kyperounda". Enfin, nous proposons l'approche de prédiction utilisée pour apprécier la production des espèces fourragères quand on irrigue avec une eau salée

Inhibition of Golgi function causes plastid starch accumulation

Little is known about possible interactions between chloroplasts and the Golgi apparatus, although there is increasing evidence for a direct Golgi to chloroplast transport pathway targeting proteins to their destinations within the membranes and stroma of plastids. Here data are presented showing that a blockage of secretion results in a significant increase of starch within plastids. Golgi disassembly promoted either by the secretory inhibitor brefeldin A or through an inducible Sar1-GTP system leads to dramatic starch accumulation in plastids, thus providing evidence for a direct interaction between plastids and Golgi activity. The possibility that starch accumulation is due either to elevated levels of cytosolic sugars because of loss of secretory Golgi activity or even to a blockage of amylase transport from the Golgi to the chloroplast is discussed

GO-PROMTO Illuminates Protein Membrane Topologies of Glycan Biosynthetic Enzymes in the Golgi Apparatus of Living Tissues

The Golgi apparatus is the main site of glycan biosynthesis in eukaryotes. Better understanding of the membrane topology of the proteins and enzymes involved can impart new mechanistic insights into these processes. Publically available bioinformatic tools provide highly variable predictions of membrane topologies for given proteins. Therefore we devised a non-invasive experimental method by which the membrane topologies of Golgi-resident proteins can be determined in the Golgi apparatus in living tissues. A Golgi marker was used to construct a series of reporters based on the principle of bimolecular fluorescence complementation. The reporters and proteins of interest were recombinantly fused to split halves of yellow fluorescent protein (YFP) and transiently co-expressed with the reporters in the Nicotiana benthamiana leaf tissue. Output signals were binary, showing either the presence or absence of fluorescence with signal morphologies characteristic of the Golgi apparatus and endoplasmic reticulum (ER). The method allows prompt and robust determinations of membrane topologies of Golgi-resident proteins and is termed GO-PROMTO (for GOlgi PROtein Membrane TOpology). We applied GO-PROMTO to examine the topologies of proteins involved in the biosynthesis of plant cell wall polysaccharides including xyloglucan and arabinan. The results suggest the existence of novel biosynthetic mechanisms involving transports of intermediates across Golgi membranes

Identification of woolliness response genes in peach fruit after post-harvest treatments

Woolliness is a physiological disorder of peaches and nectarines that becomes apparent when fruit are ripened after prolonged periods of cold storage. This disorder is of commercial importance since shipping of peaches to distant markets and storage before selling require low temperature. However, knowledge about the molecular basis of peach woolliness is still incomplete. To address this issue, a nylon macroarray containing 847 non-redundant expressed sequence tags (ESTs) from a ripe peach fruit cDNA library was developed and used. Gene expression changes of peach fruit (Prunus persica cv. O'Henry) ripened for 7 d at 21 °C (juicy fruit) were compared with those of fruit stored for 15 d at 4 °C and then ripened for 7 d at 21 °C (woolly fruit). A total of 106 genes were found to be differentially expressed between juicy and woolly fruit. Data analysis indicated that the activity of most of these genes (>90%) was repressed in the woolly fruit. In cold-stored peaches (cv. O'Henry), the expression level of selected genes (cobra, endopolygalacturonase, cinnamoyl-CoA-reductase, and rab11) was lower than in the juicy fruit, and it remained low in woolly peaches after ripening, a pattern that was conserved in woolly fruit from two other commercial cultivars (cv. Flamekist and cv. Elegant Lady). In addition, the results of this study indicate that molecular changes during fruit woolliness involve changes in the expression of genes associated with cell wall metabolism and endomembrane trafficking. Overall, the results reported here provide an initial characterization of the transcriptome activity of peach fruit under different post-harvest treatments