Extraction and characterization of new antibacterials produced by predatory actinobacteria of marine origin ; Extraction et caractérisation de nouveaux antibactériens produits par les actinobactéries prédatrices d'origine marine

This thesis work is part of the research of new ways to fight against multidrug-resistant bacteria. The approach followed is the screening of non-obligate marine predatory actinobacteria for multidrug-resistant bacteria. In this study, the isolation of predatory actinobacteria was carried out from the marine waters of the Moroccan Atlantic coast. Amongst the 142 potential predatory bacteria isolated from marine water of the Moroccan Atlantic coast, four Actinobacteria showed the aptitude to grow on agar-agar with Micrococcus luteus as the sole source of nutrients. In co-culture on solid medium, the four selected isolates showed an ability to grow on different types of bacteria cells (Gram +, Gram-) and including multidrug-resistant bacteria. However, in monoculture, the antibacterial activities in a rich medium (Bennett) was tested using agar cylinders method. The selected actinobacterial isolates showed a variable activity spectrum. Using the polyphasic approach, the taxonomic position of the four selected facultative actinobacterial predators showed that they belong to the Streptomyces genus. S. griseoflavus EMM111 strain was retained to assess its ability to prey and reduce Methicillin-resistant Staphylococcus aureus by predation. Thermochemolysis-GC-MS was used to characterize the prey and the predator through their membrane fatty acids released as methyl esters (FAMEs). The co-culture of predator and prey monitored for 15 days induced an increase in the total amount of methylated fatty acids biomarker of S. griseoflavus EMM111 thus demonstrating the predation. The last part of this work was dedicated to the extraction of the molecules involved in predation by S. griseoflavus EMM111. After fractionation, using chromatographic methods, several molecules were identified, one of it was di(2-ethylhexyl) phthalate, that has bactericidal activity. ; Ce travail de thèse s’inscrit dans le cadre de la recherche de nouveaux moyens de lutte contre les bactéries multirésistantes. L’approche suivie est le criblage ...