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Cours De Microorganismes Des Milieux Extrêmes République Algérienne Démocratique et Populaire Ministère de l’Enseignement Supérieur et de la Recherche Scientifique Université Abderahmane MIRA-Bejaia Faculté des Sciences de la Nature et de la Vie Département de Microbiologie Cours de Microorganismes des milieux extrêmes Melle DJINNI Ibtissem Maitre de Conférences Année Universitaire 2016/2017 « Les micro-organismes peuvent faire ce que vous voulez. Il suffit d’imaginer comment. » Koki HORIKOSHI « La nature a plus d’imagination que nos rêves. » Protéus, société de biotechnologie France. SOMMAIRE Listes des figures et tableaux Préface Introduction I. La diversité microbienne……………………………………………………………………….. 1 1. Les trois domaines du vivant ........................................................................................................ 1 1.1. Le domaine Bacteria…………………………………………………………………... ........... 3 1.2. Le domaine Archeae .................................................................................................................. 6 1.3. Le domaine Eucarya ................................................................................................................. 8 II. Last Universal Common Ancestor (LUCA) ................................................................................ 8 Chapitre I : L’extrêmophilie I. Notion d’extrêmophiles ................................................................................................................ 10 1. La diversité écologique ................................................................................................................ 10 2. Biodiversité des extrêmophiles .................................................................................................... 14 II. Propriétés des extrêmophiles ....................................................................................................... 17 III. Importance et applications biotechnologique des extrêmophiles .............................................. 18 1. Exploitation de l'adaptation extrêmophile .................................................................................... 18 1.1. Utilisation des cellules entières ................................................................................................. 18 1.1.1. Réduction des métaux toxiques .............................................................................................. 19 1.1.2. Oxydation et biolixiviation ..................................................................................................... 19 1.1.3. Biominéralisation et bioimmobilisation ................................................................................. 20 1.1.4. La chélation à la surface des bactéries ................................................................................... 21 1.2. Utilisation des biomolécules ..................................................................................................... 22 1.2.1. Protéines et enzymes .............................................................................................................. 22 Carboxylestérases : lipases et estérases… ......................................................................................... 23 Protéases et peptidases ..................................................................................................................... 24 Glycosidases ..................................................................................................................................... 24 Chapitre II : Les Thermophiles I. Définition et classification ............................................................................................................ 28 II. Ecologie des thermophiles .......................................................................................................... 29 1. Les biotopes naturels .................................................................................................................... 30 2. Les biotopes artificiels ................................................................................................................. 32 III. Echantillonnage et culture ......................................................................................................... 32 IV. Diversité taxonomique et métabolique ...................................................................................... 33 1. Voies métaboliques des thermophiles .......................................................................................... 35 V. Adaptations physiologiques à la thermophilie ............................................................................ 36 1. Aspects physiologiques et morphologique ................................................................................... 36 1.1. La perméabilité membranaire .................................................................................................... 37 1.2. Teneur en G+C .......................................................................................................................... 37 2. Les protéines ................................................................................................................................ 37 3. Accumulation de solutés compatibles .......................................................................................... 38 VI. Applications biotechnologiques des thermophiles .................................................................... 39 1. Conversion de la lignocellulose en hydrogène ............................................................................. 39 2. Le biofuel ..................................................................................................................................... 43 Chapitre III : Les Halophiles I. Définition et classification ............................................................................................................ 45 II. Ecologie des halophiles ............................................................................................................... 46 III. Diversité taxonomique et métabolique des microorganismes halophiles et halotolérants ........ 48 1. Les archaea halophiles ................................................................................................................. 48 2. Caractéristiques générales des archaea halophiles extrêmes ........................................................ 52 2.1. Caractères culturaux et morphologiques ................................................................................... 52 2.2. Caractères physiologiques et biochimiques… .......................................................................... 53 3. Les bactéries halophiles ............................................................................................................... 54 3.1. Taxonomie et physiologie ......................................................................................................... 54 IV. Mécanismes d’adaptation à la vie en milieu hypersalin ............................................................ 57 1. Régulation de la pression osmotique ............................................................................................ 58 2. Adaptation des protéines à l’hypersalinité ................................................................................... 59 3. Adaptation des acides nucléiques à l’hypersalinité ..................................................................... 61 V. Potentiel biotechnologique des organismes halophiles ............................................................... 62 1. Production d’enzymes .................................................................................................................. 63 1.1. Les enzymes lipolytiques .......................................................................................................... 65 1.2. Les enzymes protéolytiques ...................................................................................................... 66 1.3. Les enzymes amylolytiques ...................................................................................................... 66 Chapitre IV : Autre extrêmophiles I. Introduction ................................................................................................................................... 67 II. Les psychrophiles ........................................................................................................................ 67 1. Définition ..................................................................................................................................... 67 2. Biodiversité des microorganismes psychrophiles ........................................................................ 68 2.1. Les écosystèmes aquatiques froids ............................................................................................ 70 2.1.1. Atmosphère et nuages ............................................................................................................ 70 2.1.2. Neige ...................................................................................................................................... 70 2.1.3. Glaciers ................................................................................................................................... 71 3. Stratégies d’adaptation des microorganismes psychrophiles et leur études métaboliques .......... 71 3.1. Adaptation environnementale ................................................................................................... 72 3.2. Adaptation
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