A simple and rapid lysis method for preparation of genomic DNA from Gram-negative bacteria

A very efficient, simple and economic lysis method for rapid preparation of genomic DNA from Gramnegative bacteria was developed. This method includes a novel step lysis by treatment with carvacrol followed by simple ethanol precipitation. The procedure was realised without using of detergents or enzymes. Moreover, the resultant genomic DNA was in good quantity and quality and can be used successfully for restriction endonucleases digestion, PCR amplification and others types of molecular biology manipulations.Keywords: Genomic DNA, lysis, carvacrol, Gram-negative bacteria, Escherichia coli, Erwinia chrysanthem

Comparative study of the antifungal activity of some essential oils and their major phenolic components against Aspergillus niger using three different methods

This study aimed to evaluate the antimould activity of oregano, thyme, rosemary and clove essential oils and some of their main constituents: eugenol, carvacrol and thymol against Aspergillus niger. This antifungal activity was assessed using broth dilution, disc diffusion and micro atmosphere methods. In both agar diffusion and micro atmosphere tests, all the investigated agents showed no inhibitory effect on Aspergillus niger growth at concentrations lower than 10% (v/v). However, broth dilution test showed the highest sensitivity. Using this method, the minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) values of the tested agents were between 0.025 and 1%. The anti-Aspergillus effect of oregano and thyme oils was more potent than that of clove and rosemary oils. Concerning the phenolic compounds, thymol and carvacrol proved to have better anti-Aspergillus effect than eugenol. Accordingly, we can say that the antifungal efficacy of these agents is better appreciated when they are applied directly into liquid medium than when they are applied as volatiles or diffused in solid medium. Therefore, as these agents are active at low concentrations, they could be used in the formulation of natural preparations, and thereby could be proposed in therapeutic or hygienic contexts.Key words: Essential oils, thymol, carvacrol, antifungal activity, Aspergillus niger, micro atmosphere, agar diffusion, broth dilution

Mise en évidence de téphrites à néphéline syntectoniques dans le bassin cambrien de Sidi Saïd Maâchou (Meseta côtière, Maroc); signification géodynamique

Based on a combined structural, petrographic, and geochemical analysis, a new interpretation of the basic magmatism of Sidi Saïd Maâchou (coastal Meseta) in two stages of emplacement is proposed. The first stage is characterized by transitional pyroclastic flows that have accompanied the opening of the West-Mesetian basin, during the Cambrian; the second stage is made of dykes of basalts, dolerites, and tephrites bearing nepheline. The emplacement of this undersaturated alkaline magma is associated to a sinistral submeridian shear zone which has been activated at the end of the Caledonian orogenesis, by a mantellic advection.Basée sur des critères structuraux, pétrographiques et géochimiques, une réinterprétation du magmatisme basique de Sidi Saîd Maâchou (meseta côtière) en deux stades de mise en place est proposée. Le premier stade est caractérisé par des coulées pyroclastiques transitionnelles accompagnant l’ouverture du bassin ouest mésétien au Cambrien. Le second stade, de nature fissural, comprend des basaltes, dolérites et téphrites à néphéline spécifiques d’un magmatisme alcalin sous-saturé. La mise en place de ce dernier est associée à un couloir de cisaillement senestre subméridien activé à la fin de l’orogenèse calédonienne, engendrant un flux géothermique élevé

Effect of a natural food additive rich in thyme essential oil on methane emissions in dairy cows

L’objectif de ce travail consiste à évaluer l’effet de l’addition à la ration alimentaire, d’un additif alimentaire naturel riche en huile essentielle de thym sur la quantité de méthane émise par les vaches laitières. Le méthane est à la fois un puissant gaz à effet de serre et une vraie perte énergétique pour les ruminants. Sa réduction est bénéfique pour les animaux et pour l’environnement. Afin de tester l’effet de cet additif alimentaire naturel riche en huile essentielle de thym sur l’émission du méthane par les vaches laitières, cinq vaches de race croisées Holstein ont été utilisées, la ration alimentaire quotidienne est composée de 4 kg d’aliment concentré industriel, 2 kg de foin de luzerne et 2 kg de paille de blé. Après une adaptation de deux semaines au régime alimentaire, des mesures de la production du méthane ont été réalisées. Ensuite, 50 g du produit riche en huile essentielle de thym ont été ajoutés quotidiennement à la ration de base (soit 7,15 g/kg MS), et après deux semaines d’adaptation, une deuxième mesure du méthane a été effectuée. Un troisième essai a été réalisé en ajoutant 100 g du même produit à la même ration de base (soit 14,3 g/Kg MS), et une troisième mesure de méthane a été réalisée après les deux semaines d’adaptation. La quantité journalière de méthane produite par les cinq vaches a été estimée à environ 195,9 l/j. L’addition du produit riche en huile essentielle de thym à la ration de base a été à l’origine d’une réduction de méthane produit en moyenne de 21,6% lorsque le produit a été ajouté à la dose de 7,15 g/kg de matière sèche et de 31,8% à la dose de 14,3 g/kg de MS.  Mots clés: Additif alimentaire, Production du méthane, Huile essentielles de thym, Vache laitière, Effet de serre.The objective of this study was to evaluate the effect of a natural feed additive rich in thyme essential oil on the methane emission by the dairy cows. The methane is a powerful greenhouse gas representing a true energy loss for the ruminants and its reduction is beneficial for the animals and the environment. In order to test the effect of this natural feed additive, rich in thyme essential oil  on the emission of methane by ruminants, five dairy cattle of Holstein breed were used and received a ration composed of 4 kg of industrial concentrated feed, 2 kg of alfalfa hay and 2 kg of wheat straw with free access to drinking water. After two weeks of adaptation to the feed, measurements of the production of methane were carried out without feed additive. Then, 50 g of the product rich thyme essential oil were daily added to the basic ration (7.15 g/kg DM) during two weeks of adaptation and measurement of methane was taken in the third week. In the third period, 100 g of the same product was added to the same ration (14.3 g/Kg DM), and measurements of methane were carried out after the two weeks of adaptation. The quantity of methane produced by the five cows was estimated to average 195.9 liter/day. The addition of the product rich in thyme essential oil to the basic ration reduced methane emission on average by 21.6% when the feed additive was added with an amount of 7.15 g/kg dry matter, and a reduction on average of 31.8% with the amount was of 14.3 g/kg of dry matter. Keywords: Feed additive, Methane production, Thyme essential oil, Dairy cow, Greenhouse effect

Classical and sequential limit analysis revisited

Classical limit analysis applies to ideal plastic materials, and within a linearized geometrical framework implying small displacements and strains. Sequential limit analysis was proposed as a heuristic extension to materials exhibiting strain hardening, and within a fully general geometrical framework involving large displacements and strains. The purpose of this paper is to study and clearly state the precise conditions permitting such an extension. This is done by comparing the evolution equations of the full elastic–plastic problem, the equations of classical limit analysis, and those of sequential limit analysis. The main conclusion is that, whereas classical limit analysis applies to materials exhibiting elasticity – in the absence of hardening and within a linearized geometrical framework –, sequential limit analysis, to be applicable, strictly prohibits the presence of elasticity – although it tolerates strain hardening and large displacements and strains. For a given mechanical situation, the relevance of sequential limit analysis therefore essentially depends upon the importance of the elastic–plastic coupling in the specific case considered