Deep-sea hydrothermal vents are microbiologically well characterised, light-independent ecosystems where primary production is completely based on chemo autotrophy. In contrast, shallow water hydrothermal vents (SWHVs) have been largely ignored by microbial ecologist although these sulphide-rich vents are exciting model systems for the co-occurrence of chemoautotrophic and phototropic microbial communities. This project intends to provide an in depth picture on the biodiversity and spatial distribution of the microbial communities involved in biogeochemical cycling of sulphur at a tropical SWHV at the west coast of Dominica. For the first time, state-of-the- art, cultivation-independent techniques for microbial community analyses will be applied to such systems. The obtained data will be combined with physicochemical analyses of the SWHV fluids and the surrounding sediment. A recently developed 16S reran-based oligonucleotide micro array for the detection of all sulphate- reducing prokaryotes (Saps) will be extended to also cover all yet known oxidizing-oxidizing prokaryotes (SOPs). This DNA micro array will then be used to rapidly screen for the richness of these ecologically important sulphur- cycling microbial guilds at the SWHV. In addition, yet uncultured Saps will be identified by phylogenetic surveys of dissimulator (bi)sulphite reduces genes (drab) retrieved from the SWHV samples. Based on these data, the spatial distribution and abundance of Saps and SOPs will be quantitatively analysed by fluorescence in site hybridisation in combination with high-end confocal laser scanning microscopy and digital image analysis. These investigations on free living and benthos prokaryotes will be complemented by including prokaryotes occurring as simians of animals at the vent site. The phylogeny, abundance and distribution of the microbial simians will be analysed by 16S reran sequence retrieval and quantitative FISH.
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