Community Transcriptomics Reveals Drainage Effects on Paddy Soil Microbiome Across the Three Domains of Life
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Community transcriptomics reveals drainage effects on paddy soil microbiome across the three domains of life Dissertation zur Erlangung des akademischen Grades Doktor der Naturwissenschaften (Dr. rer. nat) dem Fachbereich Biologie der Philipps-Universität Marburg/Lahn vorgelegt von Rehab Abdallah aus Kairo, Ägypten Marburg an der Lahn | 2018 The experimental work for this thesis was carried out from October 2014 to April 2018 at the Max Planck Institute for Terrestrial Microbiology under supervision of PD Dr. Werner Liesack in the Department of Biogeochemistry and the Department of Organismic Interactions. The thesis was accepted by the Department of Biology of the Phillips University Marburg at the: 05/07/2018 First examiner: PD Dr. Werner Liesack Second examiner: Prof. Dr. Ralf Conrad Date of defense: 27/9/2018 Dedicated to my husband and my family Publication This thesis resulted in the following papers: Abdallah R. Z., Wegner C.E., Liesack W., Community transcriptomics reveals drainage effects on paddy soil microbiome across the three domains of life, (Submitted to Soil Biology and Biogeochemistry) Abdallah R. Z., Wegner C.E., Liesack W., The effect of incubation time on paddy soil microbial communities after drainage, (in preparation as short report) “Science knows no country, because knowledge belongs to humanity, and is the torch which illuminates the world” Louis Pasteur Table of contents Summary ............................................................................................................... i Zusammenfassung .............................................................................................. iii 1 Introduction .................................................................................................. 1 1.1 Methane budget, emissions, and global warming ...................................................... 1 1.2 Paddy soil and rice farming......................................................................................... 2 1.3 Biogeochemistry of rice paddies .................................................................................. 2 1.3.1 Microbial-biogeochemical cycles in surface and bulk soil ........................................ 2 Bacterial nitrogen, iron, and sulphur cycles ....................................................... 4 Soil organic matter and bio-polymer degradation in paddy soil ........................ 5 Carbohydrate Active Enzymes ........................................................................... 7 Methanogens and methanotrophs ....................................................................... 8 1.3.2 Rhizosphere soil ....................................................................................................... 10 1.4 Drainage and its importance to paddy soil .............................................................. 11 1.5 Oxygen and desiccation as environmental variables of drainage .......................... 12 1.6 Current knowledge on the response of microbial communities in paddy soil to drainage ................................................................................................................................... 13 1.7 Desiccation and oxygen as environmental stressors in pure culture studies ........ 14 1.8 Desiccation and its effect on microbial communities in other soil systems ........... 15 1.9 Molecular-ecology techniques used to assess the responses of microbial communities to environmental cues...................................................................................... 17 1.10 Engineered systems (microcosms) to study environmental stress under controlled conditions ................................................................................................................................ 18 1.11 Aim of the study and working hypothesis ................................................................ 18 2 Material and Methods ................................................................................ 20 2.1 Materials ..................................................................................................................... 20 2.1.1 Soil sample ............................................................................................................... 20 2.1.2 Instruments used ....................................................................................................... 20 2.1.3 Chemicals and reagents ............................................................................................ 21 2.1.4 Kits ........................................................................................................................... 22 2.2 Methods ....................................................................................................................... 23 2.2.1 Microcosm preparation, incubation, and drainage ................................................... 23 2.2.2 Sampling ................................................................................................................... 23 2.2.3 Measurement of soil physical and chemical parameters .......................................... 25 2.2.4 DNA and total RNA extraction and quality assessment .......................................... 26 2.2.5 cDNA synthesis and Illumina sequencing ............................................................... 26 2.2.6 qPCR and RT-qPCR................................................................................................. 27 2.2.7 Computational analysis ............................................................................................ 28 Demultiplexing and quality control .................................................................. 28 Extraction of SSU rRNA and mRNA datasets ................................................. 28 Diversity analyses ............................................................................................ 28 Analysis of SSU rRNA reads ........................................................................... 28 Analysis of mRNA transcripts ......................................................................... 29 2.2.8 Analysis of differential drainage effects .................................................................. 30 2.2.9 Statistical analysis and figures generation ............................................................... 30 3 Results .......................................................................................................... 31 3.1 Soil physical and chemical parameters .................................................................... 31 3.2 Sampling, extraction and purification of total RNA ............................................... 32 3.3 Absolute abundance of Bacteria, Archaea, and Fungi ............................................ 33 3.4 cDNA synthesis for Illumina RNA-Seq .................................................................... 33 3.5 Sequencing statistics of Illumina RNA-Seq ............................................................. 34 3.6 Effect of drainage on the microbial community composition ................................ 37 3.6.1 Microbial diversity and richness .............................................................................. 37 3.6.2 Drainage effects on domain level (Bacteria, Archaea, and Eukarya) ..................... 38 3.6.3 Effect of drainage on bacterial community composition ......................................... 39 3.6.4 Effect of drainage on archaeal community composition .......................................... 41 3.6.5 Effect of drainage on eukaryotic community composition ...................................... 41 3.7 Effect of drainage on community functioning ......................................................... 42 3.7.1 Effect of drainage on the gene expression of particular functional categories ........ 42 General cellular processes and stress response genes ...................................... 42 Transcripts involved in methane cycling ......................................................... 44 Plant bio-polymer degradation ......................................................................... 44 3.8 The impact of the pre-incubation period on the community response to drainage 48 3.8.1 The effect of pre-incubation period on SSU rRNA level ......................................... 48 3.8.2 The effect of pre-incubation period on mRNA level ............................................... 53 4 Discussion .................................................................................................... 58 4.1 Effects of drainage on soil physical and chemical parameters............................... 59 4.2 Effects of drainage on absolute abundance of Bacteria, Archaea, and Fungi....... 59 4.3 The use of a ‘double RNA approach’ – Illumina RNA sequencing (RNA-Seq) and computational analysis ........................................................................................................... 60 4.4 The development of drainage-specific microbial communities in paddy soil ....... 61 4.5 SSU rRNA dynamics versus mRNA turnover ......................................................... 64 4.6 Environmental factors driving drainage-induced community change .................. 65 4.7 Drainage-induced changes in functional gene expression ...................................... 68 4.7.1 Cellular processes: Decrease in cell motility but increase in transcription and translation ............................................................................................................................