Bright, Monika
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Bright, Monika
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Bright, Monika
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Item-typ:Veröffentlichung, The Bacterial Ectosymbionts of the Ciliate Kentrophoros(2017-10-24); ; ; Kentrophoros is a single-celled eukaryote that has a symbiosis with sulfur-oxidizing bacteria. This thesis investigates the diversity and functional significance of this symbiosis through molecular ecology and genomics. The bacteria belong to a single lineage in the Gammaproteobacteria that is specifically associated with Kentrophoros. Kentrophoros also constitutes a monophyletic group, despite their morphological diversity, which includes new species discovered during this work. Mitochondrial genes of Kentrophoros show evidence of rapid diversification during their evolutionary history. Genomes of the symbionts encode pathways for sulfur oxidation, but none of the known pathways for autotrophic carbon fixation. Instead they have the genetic potential for uptake and usage of organic carbon substrates, suggesting that this symbiosis is based on chemolithoheterotrophy, instead of chemosynthesis, as previously thought. The ecophysiological consequences of such a metabolism are discussed.Dissertation578 835 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Transmission of bacterial symbionts in the gutless oligochaete Olavius algarvensis(2016-01-27); ; ; The essential role that symbioses between bacteria and animals play for life on earth has been a major topic of scientific research for the past fifty years. We now understand that eukaryotic life could not have evolved without the intricate influence of bacteria, which impact physiological, metabolic, nutritional, developmental and evolutionary processes in many eukaryotic phlya. One model system for such associations is the well-studied symbiosis between the gutless oligochaete Olavius algarvensis, from the island of Elba, Italy, and its obligate consortium of chemoautotrophic sulphide-oxidizing gamma-proteobacteria and sulphate reducing delta-proteobacteria. The complete nutritional dependency of the host to its symbionts has led to the reduction of the digestive tract and the excretory system. The aim of this thesis is to investigate how this symbiosis is maintained over consecutive generations. In particular I examine whether symbionts are transmitted into the next host generation vertically by smearing from the parent worm during oviposition, horizontally by uptake from the environment, or by both these modes. To answer this question further investigation into worm ecology, development and molecular methodological advancement had to be made.Dissertation463 249 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Acquisition and activity of bacterial symbionts in marine invertebrates(2012-10-26); ; ; Chemosynthetic symbioses evolved multiple times in a wide diversity of host species and from many different bacterial lineages. The symbionts provide nutrition to the hosts by fixing CO2 into biomass using reduced inorganic compounds as energy sources. This gives the hosts a physiological advantage to colonize and thrive in nutrient poor habitats. Two key questions that have emerged in symbiosis research are 1) how do the hosts acquire their symbionts and 2) what reduced compounds can be used by the symbionts as energy source to fix CO2 into biomass. This PhD thesis consists of two parts that will each deal with one of these two fundamental questions. In the first part of this thesis, two manuscripts describe the symbiont colonization of host tissues in the deep-sea mussel Bathymodiolus from hydrothermal vents. Bathymodiolus harbors its chemosynthetic symbionts intracellularly in gill tissues and, as in all bivalves, the gills grow throughout the mussel's life. This raises the question how the newly developed gill tissues are colonized by symbionts. Symbiont colonization of newly formed gill tissues was investigated using fluorescence in situ hybridization with symbiont-specific probes on semi-thin sections of whole juveniles. In addition, posterior ends of adult gills were also analyzed, as new gill filament formation occurs here. In the smallest juveniles, symbionts had colonized a wide range of epithelial tissues, revealing a widespread distribution of symbionts in many different juvenile organs. In contrast, juveniles larger than 9 mm had symbionts only in their gills. These observations indicate an ontogenetic shift in symbiont colonization from an indiscriminate infection of almost all epithelia in early life stages to spatially restricted colonization of gills in later developmental stages of Bathymodiolus. Analyses of the posterior end of both juvenile and adult gill tissues further showed that all gill filaments except the first most recently formed 7 to 9 filaments harbored symbionts. Newly formed gill tissues of Bathymodiolus are thus initially symbiont free and only later become infected with symbionts as they extend and differentiate, suggesting a life long de novo colonization by the endosymbionts of aposymbiotic host cells. In the second part of this thesis I investigated the physiological capabilities of the symbionts of Olavius algarvensis. This marine worm lacks both a digestive and excretory system. Instead it relies on a symbiotic community of two gammaproteobacterial sulfur oxidizers, two deltaproteobacterial sulfate reducers, and a spirochete for nutrition and waste recycling. External energy sources for the symbiotic association have remained enigmatic because of extremely low concentrations of reduced sulfur compounds and organic substrates in the worms habitat. Using a metaproteomic approach and incubation experiments I showed that hydrogen (H2) and carbon monoxide (CO) are additional energy sources for the symbiosis of O. algarvensis. The finding of elevated CO and H2 concentrations in the worm s habitat further confirmed the ecological importance of both substrates for the worm symbiosis. One of the sulfur-oxidizing symbionts incorporated high amounts of CO2 into its biomass in the presence of CO, which was determined using 13C-labeled bicarbonate in the incubation medium and subsequent nanoSIMS analyses. The metaproteomic study further revealed a high expression of proteins involved in highly efficient pathways and high-affinity uptake transporters for the recycling and conservation of energy, nitrogen, and carbon sources. This indicates that the nutrient-poor nature of the worm s habitat exerted a strong selective pressure in shaping this association.Dissertation216 149 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Characterization of host-symbiont molecular interactions and evolutionary relationships in the gutless oligochaete Olavius algarvensis(2016-06-01); ; ; The marine gutless oligochaete O. algarvensis lives in obligate symbiosis with a chemosynthetic bacterial consortium that exclusively provides it with nutrition. This thesis contributes to a better understanding of how this essential symbiosis is maintained, both on a physiological and immunological level (chapter IV), as well as from an evolutionary perspective (chapter II). This is addressed by using metagenomics, -proteomics and -transcriptomics to better understand symbiont transmission, diversity, co-divergent evolution and the molecular adaptations of the host that allow it to intimately associate with a diverse and physiologically demanding chemosynthetic consortium (anoxia and noxious substances). Furthermore, chapter III provides the first functional genomic description of the spirochaetal symbiont of O. algarvensis, showing that it is most likely a beneficial symbiont involved in the utilization and funneling of environmentally derived organic nutrients into the symbiosis.Dissertation332 183