Masterarbeit / Master's Thesis
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MASTERARBEIT / MASTER’S THESIS Titel der Masterarbeit / Title of the Master‘s Thesis Description of two novel and as-yet uncultured endosymbionts of Acanthamoeba spp. verfasst von / submitted by Stefanie Michels BSc angestrebter akademischer Grad / in partial fulfilment of the requirements for the degree of Master of Science (MSc) Wien, 2016 / Vienna 2016 Studienkennzahl lt. Studienblatt / A 066 830 degree programme code as it appears on the student record sheet: Studienrichtung lt. Studienblatt / Masterstudium Molekulare Mikrobiologie, mikrobielle degree programme as it appears on Ökologie und Immunbiologie the student record sheet: Betreut von / Supervisor: Univ.-Prof. Dr. Matthias Horn 2 Table of content 1. Introduction ......................................................................................................................................... 7 1.1 Endosymbiosis and other definitions ............................................................................................. 7 1.2 Diversity of bacterial endosymbionts in free-living amoebae ........................................................ 8 1.3 General physiology of bacterial endosymbiosis ........................................................................... 11 1.3.1 The intracellular life-style ...................................................................................................... 11 1.3.2 Chlamydial metabolism and physiologic activity .................................................................. 12 1.4 Aim of the study ........................................................................................................................... 15 2. Material and Methods ........................................................................................................................ 17 2.1 Technical supply and computer software .................................................................................... 17 2.2 Consumables ................................................................................................................................ 18 2.3 Molecular biology kits .................................................................................................................. 18 2.4 Probes and primers ...................................................................................................................... 19 2.5 Growth media, buffers and other chemical solutions .................................................................. 20 2.6 Methods ....................................................................................................................................... 24 2.6.1 Isolation of amoebae of free-living amoebae using non-nutrient agar plates seeded with food bacteria ..................................................................................................................................... 24 2.6.2 Axenization of free-living amoebae ...................................................................................... 25 2.6.3 Fluorescence in-situ hybridization (FISH) .............................................................................. 25 2.6.4 16S rRNA gene sequencing of axenized amoeba cultures .................................................... 26 2.6.5 Cultivation of identified Acanthamoeba spp. HSC ................................................................ 31 2.6.6 Curing of Acanthamoeba spp. HSC ....................................................................................... 31 2.6.7 Defining the host range of endosymbionts ........................................................................... 32 2.6.8 Isolation of genomic DNA ...................................................................................................... 32 2.6.9 HeLa cell infection assay ....................................................................................................... 33 2.6.10 Growth comparison ............................................................................................................ 34 2.6.11 Infection cycles ................................................................................................................... 36 3 2.6.12 Extracellular infectivity Assay ............................................................................................. 37 2.6.13 Glucose Assay ..................................................................................................................... 38 3. Results ................................................................................................................................................ 41 3.1 Isolation of free-living amoebae using non-nutrient agar plates seeded with Gram-negative food bacteria and axenic cultivation .............................................................................................................. 41 3.2 Identification of novel endosymbionts of Acanthamoeba spp. ................................................... 42 3.2.1 Fluorescence in-situ hybridization results ............................................................................. 42 3.2.2 16S/18S rRNA gene sequencing results of amoeba cultures harboring endosymbionts ...... 43 3.3 Phylogenetic analysis ................................................................................................................... 45 3.4 Host range of the endosymbionts HSC3 and HSC8 ...................................................................... 47 3.4.1 Curing of the natural Acanthamoeba sp. HSC host ............................................................... 47 3.4.2 Infection of different Acanthamoeba spp., human and insect cell lines ............................... 48 3.5 Characterization of Endosymbiont of Acanthamoeba sp. HSC3 .................................................. 49 3.5.1 The endosymbiont HSC3 has a biphasic infection cycle ........................................................ 49 3.5.2 Uninfected Acanthamoeba sp. HSC show faster growth in comparison to acanthamoebae harbouring the endosymbiont HSC3 ................................................................................................. 51 3.5.3 Influence of the endosymbiont HSC3 on acanthamoeba viability ........................................ 53 3.5.4 Influence of nutrient availability on infectivity ..................................................................... 55 3.6 Endosymbiont of Acanthamoeba sp. HSC8 .................................................................................. 58 3.6.1 The infection cycle of endosymbiont HSC8 ........................................................................... 58 3.6.2 Uninfected Acanthamoeba sp. HSC show faster growth in comparison to acanthamoebae harbouring the endosymbiont HSC8 ................................................................................................. 61 3.6.3 Influence of the endosymbiont HSC8 on acanthamoeba viability ........................................ 63 3.6.4 Maintenance of infectivity during host-free incubation ....................................................... 65 4. Discussion ........................................................................................................................................... 69 4.1 Detection of endosymbionts of free-living amoebae .................................................................. 69 4.1.1 Isolation and axenization of free-living amoebae ................................................................. 69 4.1.2 Detection of endosymbionts within free-living amoebae using FISH ................................... 69 4.2 Identification and phylogenetic analysis of endosymbionts of Acanthamoeba sp. ..................... 70 4.3 Curing of natural Acanthamoeba spp. HSC host .......................................................................... 72 4.4 Host range of endosymbionts of Acanthamoeba spp. HSC3 and HSC8 ...................................... 73 4.4.1 HSC3 and HSC8 are able to infect a variety of Acanthamoeba spp. ..................................... 73 4 4.4.2 HSC3 and HSC8 are incapable to infect mammalian and insect cells .................................... 74 4.5 Characterization of the endosymbiont of Acanthamoeba sp. HSC3 ............................................ 76 4.5.1 The developmental cycle of the chlamydia HSC3 ................................................................. 76 4.5.2 Influence of the endosymbiont on growth and fitness of amoebae hosts ........................... 78 4.5.3 Host-free survival capability and maintenance of infectivity in relation to nutrient availability .......................................................................................................................................... 80 4.6 Characterization of the endosymbiont of Acanthamoeba sp. HSC8 ............................................ 82 4.6.1 The infection cycle of the endosymbiont HSC8 .................................................................... 82 4.6.2 Influence of the endosymbiont on growth and fitness of amoebae hosts ........................... 84 4.6.3 Host-free survival capacity and maintenance of infectivity .................................................. 86 5. Abstract .............................................................................................................................................. 89 6. Zusammenfassung .............................................................................................................................. 91 Appendix ...................................................................................................................................................