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Notre étude a porté sur six souches d’Escherichia coli (BL 21, JM 105, JM 109, HB 101 et XL blue) dont E.Coli (BL 21) est lysogène pour le bactériophage 𝛌. D’abord, nous avons vérifié les caractéristiques morphologiques et physiologiques des souches d’E.Coli utilisées et, aussi confirmer leurs résistances ou sensibilités à l’antibiotique qui est l’acide nalidixique appartenant à la famille des quinolones. Ensuite, nous avons réalisé l’induction du phage 𝛌 chez la bactérie lysogène BL21 via les rayons UV en milieu liquide afin de déterminer la dose d’irradiation qui induit le cycle lytique et qui était d’1 minute pour une distance de 19 cm de la source des rayons UV (puissance 30 w et une longueur d’onde de 254 nm). Enfin, nous avons décrit les mécanismes génétiques intervenant lors de l’induction physique qui est un commutateur entre lysogénie et virulence.

 
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Soil salinity is an important abiotic stress which significantly affects seedling growth and seed quality. Legumes are very important plants both ecologically and agriculturally because they are able to interact symbiotically with rhizobia for biological nitrogen fixation. Before beginning the experimental part of the thesis, we conducted a bibliographic search that describes the biological approach to adaptation to salinity of Medicago truncatula Gaertn., Genetic and physiological standpoint. In order to have more information on early seedling development under salinity stress, it will be interesting to examine radicle growth in comparison to plumule elongation under different salinity stress conditions. In this study, we assessed the variability of four genotypes of the plant model Medicago truncatula under four levels of salt stress (distilled water as control 0, 68, 102 and 137 mM) of sodium chloride (NaCl) solution. In order to evaluate the degree of radicle sensitivity, we measured the plumule length to radicle length ratio. Also, we investigated the relationship between storage protein content, seed weight and salinity tolerance degree. The results show that Tru 131 and Tru 673 genotypes, with a low ratio and high storage protein content, are more tolerant to salinity stress than the sensitive genotypes Tru 26 and Jemalong. We concluded that the most tolerant genotype Tru 131 with rich protein and high seed weight can be cultivated in saline and semi-arid areas in Algeria and Mediterranean regions to improve the legumes productivity. Although, the genotype Tru 673 that had a low seed vigour, appear tolerant (low ratio) despite coming from ‘aged seeds’. This additional data shows the influence of ‘aged seeds’ on seed vigour and root growth because seeds contain all of the genetic resources of the plant. Seed storage proteins from four genotypes of the plant model Medicago truncatula were electrophoretically separated by SDS-PAGE in order to find protein bands as markers for genotypes characterization in relation to salt stress. A total of 20 protein bands with molecular weight ranging from 10 to > 80 kD were recorded. Among the genotypes, the tolerant genotype (Tru 131) represented maximum number of protein bands. The clustering by UPGMA showed variability between the genotypes studied and are assembled into three groups. The variability of protein profiles suggested that these selected genotypes can be a good source for crop improvement through hybridization programs. The data analysis of germination aptitude showed that the Tru 131 genotype had the best germinatif ability, compared to (Jemalong). The soluble protein analysis, showed a high protein synthesis during salt stress application in the tolerant genotype compared to the sensitive one (Jemalong). The results showed also that the tolerant genotype T131 expresses a better root growth compared to Jemalong with a high guaiacol peroxidase activity, which has a protective role against the molecules (ROS) accumulated during oxidative stress. The analysis of antioxidants in the case of high salinity shows increasing quantity of ascorbate (ASC-DHA) and Glutathione (GSH-GSSG) in the tolerant genotype T131. At the molecular level and in order to position 9 new accessions of the model species Medicago truncatula compared to the two contrasting genotypes to salt stress (Tru 131 and Jemalong), molecular analysis using four EST-SSR markers was performed. The results showed a moderate genetic diversity among different accessions of Medicago truncatula studied. This work requires an agronomic characterization with salt stress in order to find relationship between the EST-SSR markers and phenotype for salt stress tolerance

 
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In our study, we assessed the phenotypic variability of eleven ecotypes of M. truncatula Gaertn. under salt stress (137 mM NaCl) compared to the control at the germination stage. For the analysis of seedling growth under salinity stress, it will be useful to study root growth elongation. Several studies are focalized in root development because it is the most sensitive part of the plant and controls rapid transmission information to other plant parts. The Results showed that Tru 131 ecotype, with a high ratio (Root more vigorous than shoot) is more tolerant to salinity stress than the sensitive ecotypes. For the molecular analysis, four expressed sequence tag-simple sequence repeat EST-SSRs primers (MTIC 044, MTIC 124, MTIC 077 and MTIC 335) were used to show genetic variability in different ecotypes of M. truncatula Gaertn. Comparing with the two contrasting genotypes Tru 131, tolerant genotype and Jemalong, sensitive one. The polymorphic information content (PIC) ranged from 0.12 to 0.49. These EST-SSRs markers were more polymorphic except MTIC 044. We have chosen the most polymorphic EST-SSR (MTIC124) in order to determine a potential link between this marker and salt stress tolerance. The results obtained from “ Unigene and Uniprot” databases of highly similarity proteins sequences with the EST- SSR (MTIC 124), showed that this locus encode cysteine proteinase inhibitor, and was expressed principally in root in M. truncatula. This data suggest that this locus is involved in salinity tolerance, and it is appropriate for understanding salt stress tolerance mechanisms in Medicago truncatula Gaertn.

 
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Legumes are very important plants both ecologically and agriculturally because they are able to interact symbiotically with rhizobia for biological nitrogen fixation and soil fertilization. Medicago truncatula Gaertn. is an important model legume rich in protein. Salinity represents, today, the major cause of land degradation and crop productivity limitation around the world and affects physiology and metabolism in legumes. In this study, we analyzed the physiological and biochemical responses of rootlets in two contrasting ecotypes of Medicago truncatula (Tru 131, tolerant and Jemalong, sensitive) to different level of NaCl, (68, 102 and 137 mM). Results showed that the tolerant ecotype has a lower water potential than Jemalong. Root protein content of Tru 131 was decreased than Jemalong, this can be explained by accumulation of protein oxidation in the sensitive genotype. Moreover, NaCl increased guaiacol peroxidase activity GPX in rootlets of Tru 131, this enzyme has a protective role against the molecules ROS accumulated during oxidative stress. On the other hand, under salt stress the total content of ascorbate (ASC + DHA) and Glutathione (GSH + GSSG) was increased in the tolerant genotype Tru 131 compared to Jemalong. These results show how the tolerant genotype activate the antioxidative defense system at root level against damages caused by oxidative stress under salinity.

 
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En Algérie, les sols sont soumis à une forte érosion hydrique due aux conditions climatiques drastiques qui diminuent le couvert végétal. Cette érosion affecte plus de 28 % des terres de l’Algérie du Nord. Ce sont les terres à fortes pentes des massifs telliens qui sont les plus touchées (Hadjiat, 1997 ; Nedjraoui, 2003). Sur ces sols nus en pente, l’utilisation des espèces annuelles à resemis naturel et des légumineuses herbacées pérennes doit être fortement encouragée (Abdelguerfi et al., 2008). A cet effet, la culture des légumineuses comme la luzerne, s’avère une bonne alternative pour contrer les aléas fréquents de l’environnement tels que les stress abiotiques afin de contribuer efficacement à la lutte contre les changements climatiques.

 
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I'm Postdoctoral researcher, i'm interested in differents areas of plant breeding in relationship to abiotic stress plant and Soil Sciences-Plant Breeding -Abiotic Stress-Bioinformatics-Genomics-Agronomy and crop science-Plant physiology-Seed science-Legume

Address: Plant Ecology Laboratory. Department of Biology.
BP 1524. Faculty of SNV. University of Oran 1 Ahmed Ben Bella.
31000-Oran –Algeria

[ Modifié: jeudi 2 avril 2020, 23:33 ]
 
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TCE L1 COURS 5

[ Modifié: jeudi 2 avril 2020, 18:10 ]
 
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Dear students

You will find the 4th lesson entitled FOOD CHAINS AND FOOD WEBS attached here. The other lessons will be posted as soon as possible. Even the key answers will be given, but at least try to do the tasks before getting the answers.

Much of success.

Your teacher

K. KHALLADI

[ Modifié: jeudi 2 avril 2020, 18:11 ]
 
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مقال مهم تناول فيه صاحبة العلاقة الجدلية بين التصوف والروج جوهرا وعقلا

 
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كتاب مهم نهج فيه صاحبه منهج الاخباريين القدامى،، والكتاب يدخل ضمن ما يعرف بعلم الجفر أو الجفريات وتناول فيه 

صاحبه موضوع دخول الفرسيين إلى البلاد العربية(مصر والجزائر)

وذكر جرائمهم وأفعالهم مع حاكمهم الطاغية آنذا نبليون بونابرت

كما يتنبئ فيه بدخول الفرنسيين إلى الجزائر.