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

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

Bacterial Flagella: Twist and Stick, or Dodge across the Kingdoms

The flagellum organelle is an intricate multiprotein assembly best known for its rotational propulsion of bacteria. However, recent studies have expanded our knowledge of other functions in pathogenic contexts, particularly adherence and immune modulation, e.g., for Salmonella enterica, Campylobacter jejuni, Pseudomonas aeruginosa, and Escherichia coli. Flagella-mediated adherence is important in host colonisation for several plant and animal pathogens, but the specific interactions that promote flagella binding to such diverse host tissues has remained elusive. Recent work has shown that the organelles act like probes that find favourable surface topologies to initiate binding. An emerging theme is that more general properties, such as ionic charge of repetitive binding epitopes and rotational force, allow interactions with plasma membrane components. At the same time, flagellin monomers are important inducers of plant and animal innate immunity: variation in their recognition impacts the course and outcome of infections in hosts from both kingdoms. Bacteria have evolved different strategies to evade or even promote this specific recognition, with some important differences shown for phytopathogens. These studies have provided a wider appreciation of the functions of bacterial flagella in the context of both plant and animal reservoirs

Cyanide effluent treatment by electrocoagulation using airlift reactor: Modeling and optimization by response surface methodology

The extraction processes of gold, silver, and various metals from ores consume 13% of 1.1 million metric tons of hydrogen cyanide produced worldwide annually. Therefore, developing efficient processes to treat the issuing effluents before releasing them into the environment is imperative. In this context, the present study aims to evaluate the effect of three factors: inter-electrodes distance (d), current density (J) and electrolysis time (t) on the cyanide removal efficiency by a combination between Electro-Coagulation process and Internal Loop Airlift Reactor. Employing an airlift reactor enables an effective dispersion of the coagulant without the need for additional stirring. The optimization of the process was conducted using Response Surface Methodology in conjunction with Box–Behnken Design. The statistical analysis results reveal that electrolysis time(t)and current density (J) have significant effects on reactor performance to reduce cyanide with a confidence level of 99%, and 97.5%, respectively. The multiple regression analysis method demonstrates the model's overall predictability as the coefficient of determination was 98 % for the cyanide removal efficiency. The investigation inside the RSM 2 and 3-dimensional graphs allowed us to define the optimal domains of the variables to reduce cyanide. At a current density of 68 A.m−2 and an inter-electrodes distance of 13mm during 57.5min of electrolysis time, 98.27% of cyanide removal is achieved. The knowledge obtained through this study using the airlift reactor operating in batch mode and the EC process for the treatment of cyanide effluent confirms EC's ability to successfully remove cyanide and might be useful for the transposition from batch to continuous mode

Cell wall characteristics and structure of hydrated and dry leaves of the resurrection plant Craterostigma wilmsii, a microscopical study.

The cell wall architecture of leaf tissues of the resurrection plant Craterostigma wilmsii at various stages of dehydration and rehydration was studied using electron microscopy and immunocytochemistry with antibodies to a hemicellulose (xyloglucan) and pectins. Upon dehydration, the cell walls were shown to fold extensively. It is thought that this folding may prevent excessive mechanical stress developing between the cell wall and the plasmalemma. Our immunocytochemical results show a significant increase in labelling of xyloglucan and unesterified pectins in the cell wall during drying, with levels declining again during rehydration. These components are known to play an important structural role within the cell wall, giving it more tensile strength. It is hypothesised that this increase in tensile strength allows the cell wall to contract and then fold as the plant dries and ultimately prevents the total inward collapse of the cell walls in dry tissue. The increased tensile strength may also be necessary to prevent the cell wall from unfolding and expanding too rapidly upon rehydration, thus allowing plasmalemma-cell wall connections to be reestablished