Titre :	Identification polyphasique des souches d’actinobactéries isolées d’échantillons de sols semi-arides : Caractérisation structurale des antibiotiques produits.
Type de document :	texte imprimé
Auteurs :	Nassima Leulmi, Auteur ; Abderrahmane Boulahrouf, Directeur de thèse
Editeur :	جامعة الإخوة منتوري قسنطينة
Année de publication :	2018
Importance :	174 f.
Format :	30 cm.
Note générale :	2 copies imprimées disponibles
Langues :	Français (fre)
Catégories :	Français - Anglais Biologie
Tags :	Actinobactéries  Streptomyces  sols semi-arides  antibiotiques  polyéthers ionophores  cytotoxicité  Actinobacteria  Semi-arid soils  Antibiotics  ionophoric polyethers  Cytotoxicity  الاكتينوبكتيريا  ترب شبه جافة  المضادات الحيوية  polyéthers  ionophores التسمم الخلوي
Index. décimale :	570 Sciences de la vie. Biologie
Résumé :	Actinobacteria are a group of filamentous bacteria, mainly inhabit the soil. They are known for producing a wide variety of bioactive molecules, especially antibiotics. Is in this context that our research work focused. A total of 99 isolates were recovered from a semi-arid soi,collected from; rhizospheric associated soil (Khenchela), mountain soil (Mount chélia region, khenchela) and Sebkha soil (Oum El bouaghi). Three strains (SF10, SFKH4 and SFKH10), were selected, based on preliminary screening for antimicrobial activity. The isolates were identified as belonging to the genus Streptomyces, based on phenotypic and chemotaxonomic study. Phylogenetic analysis revealed that the strains SF10, SFKH4 and SFKH10 were most closely related to Streptomyces youssoufiensis, Streptomyces spororaveus and Streptomyces coeruleorubidus with a pairwise 16S rRNA gene sequence similarity of 99, 8, 99 % and 99%. Ethyl acetate extracts provied by the culture of the strains on solid culture were tested for their antimicrobial activity against the test microorganisms. The structure elucidation of the biologically active molecules, purified by different chromatographic methods, was carried out by coupling several techniques of mass spectrometry and Nuclear Magnetic Resonance (1H NMR, 13C NMR, MS, MS tandem, IR and UV-Visible). Streptomyces youssoufiensis SF10 strain produced several molecules belonging to ionophoric polyethers family, abierixin, nigericin, epinigericin, and the newly isolated grisorixin methyl ester. Moreover, only one molecule, belonging to macrotetrolides family (dinactin), was obtained from Streptomyces coeruleorubidus SFKH10 strain. In addition, the partial characterization of the molecules secreted by S. spororaveus SFKH4 strain has shown its capacity to produce a large variety of complexes compounds having high molecular weight. The presence of epimeric forms of nigericin/epinigericin and grisorixin/epigrisorixin has spurred DFT (Density Functional Theory) computational calculations. This analysis was able to provide the relative stability of the most favored epimers. This consideration is of general interest and can be applied to the wide class of naturally occurring polycyclic polyethers. On the other hand, the study of the cytotoxicity of the purified and identified molecules revealed that both nigericin and grisorixin methyl ester showed to affect glioblastoma stem cells proliferation in a dose-dependent manner, with a higher activity for the more lipophilic grisorixin methyl ester (IC50 values of 3.85 and 3.05 μM for VIPI and COMI humain glioblastoma stem cells, respectively). In conclusion, the present study has revealed the potential of semi-arid Algerian ecosystems as a good source for bioactives molecules-producing actinobacteria, specialy Streptomyces youssoufienisis SF10 strain whose secondary metabolites profile has not been studied so far by bioguided method. The clear antiproliferative activity of grisorixin methyl ester on glioblastoma stem cells represents a promising starting point aimed to the development of new drug candidates in the treatment of glioblastoma multiforme.
Diplôme :	Doctorat en sciences
Permalink :	https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=11029

Identification polyphasique des souches d’actinobactéries isolées d’échantillons de sols semi-arides : Caractérisation structurale des antibiotiques produits. [texte imprimé] / Nassima Leulmi, Auteur ; Abderrahmane Boulahrouf, Directeur de thèse . - جامعة الإخوة منتوري قسنطينة, 2018 . - 174 f. ; 30 cm.
2 copies imprimées disponibles

Langues : Français (fre)

Catégories :	Français - Anglais Biologie
Tags :	Actinobactéries  Streptomyces  sols semi-arides  antibiotiques  polyéthers ionophores  cytotoxicité  Actinobacteria  Semi-arid soils  Antibiotics  ionophoric polyethers  Cytotoxicity  الاكتينوبكتيريا  ترب شبه جافة  المضادات الحيوية  polyéthers  ionophores التسمم الخلوي
Index. décimale :	570 Sciences de la vie. Biologie
Résumé :	Actinobacteria are a group of filamentous bacteria, mainly inhabit the soil. They are known for producing a wide variety of bioactive molecules, especially antibiotics. Is in this context that our research work focused. A total of 99 isolates were recovered from a semi-arid soi,collected from; rhizospheric associated soil (Khenchela), mountain soil (Mount chélia region, khenchela) and Sebkha soil (Oum El bouaghi). Three strains (SF10, SFKH4 and SFKH10), were selected, based on preliminary screening for antimicrobial activity. The isolates were identified as belonging to the genus Streptomyces, based on phenotypic and chemotaxonomic study. Phylogenetic analysis revealed that the strains SF10, SFKH4 and SFKH10 were most closely related to Streptomyces youssoufiensis, Streptomyces spororaveus and Streptomyces coeruleorubidus with a pairwise 16S rRNA gene sequence similarity of 99, 8, 99 % and 99%. Ethyl acetate extracts provied by the culture of the strains on solid culture were tested for their antimicrobial activity against the test microorganisms. The structure elucidation of the biologically active molecules, purified by different chromatographic methods, was carried out by coupling several techniques of mass spectrometry and Nuclear Magnetic Resonance (1H NMR, 13C NMR, MS, MS tandem, IR and UV-Visible). Streptomyces youssoufiensis SF10 strain produced several molecules belonging to ionophoric polyethers family, abierixin, nigericin, epinigericin, and the newly isolated grisorixin methyl ester. Moreover, only one molecule, belonging to macrotetrolides family (dinactin), was obtained from Streptomyces coeruleorubidus SFKH10 strain. In addition, the partial characterization of the molecules secreted by S. spororaveus SFKH4 strain has shown its capacity to produce a large variety of complexes compounds having high molecular weight. The presence of epimeric forms of nigericin/epinigericin and grisorixin/epigrisorixin has spurred DFT (Density Functional Theory) computational calculations. This analysis was able to provide the relative stability of the most favored epimers. This consideration is of general interest and can be applied to the wide class of naturally occurring polycyclic polyethers. On the other hand, the study of the cytotoxicity of the purified and identified molecules revealed that both nigericin and grisorixin methyl ester showed to affect glioblastoma stem cells proliferation in a dose-dependent manner, with a higher activity for the more lipophilic grisorixin methyl ester (IC50 values of 3.85 and 3.05 μM for VIPI and COMI humain glioblastoma stem cells, respectively). In conclusion, the present study has revealed the potential of semi-arid Algerian ecosystems as a good source for bioactives molecules-producing actinobacteria, specialy Streptomyces youssoufienisis SF10 strain whose secondary metabolites profile has not been studied so far by bioguided method. The clear antiproliferative activity of grisorixin methyl ester on glioblastoma stem cells represents a promising starting point aimed to the development of new drug candidates in the treatment of glioblastoma multiforme.
Diplôme :	Doctorat en sciences
Permalink :	https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=11029