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Abstract

Besides their challenging and ancient energy metabolism, and applied relevance, much of the interest in sulphate-reducing bacteria arises from their ecophysiological significance in marine environments (Widdel, 1998). In the biologically highly active shelf sediments they contribute to more than 50% of organic carbon remineralization (Jørgensen, 1982), which can only be explained by complete substrate oxidation (Fenchel and Jørgensen, 1977). While this capacity is not present among the frequently isolated and intensively studied Desulfovibrio spp., it could be demonstrated with e.g. the newly isolated Desulfobacter postgatei (Widdel and Pfennig, 1981) and Desulfobacterium autotrophicum (Brysch et al., 1987). The latter employs the C1/CO-dehydrogenase pathway for complete oxidation of acetate to CO2 as well as for CO2-fixation (Schauder et al., 1989). Most of the known sulphate-reducing bacteria can be grouped into the two deltaproteobacterial families Desulfovibrionaceae (Devereux et al., 1990) or Desulfobacteriaceae (Widdel and Bak, 1992). This phylogenetic distinction is to a large extent paralleled by the capacities for incomplete (to acetate) and complete (to CO2) oxidation of organic substrates, respectively. At present, more than 450 prokaryotic genomes have been completely sequenced and about 1000 further prokaryotic genomes are in progress (http://www.genomesonline.org). While most genome projects primarily reflect biotechnological or biomedical research interests, environmentally relevant microorganisms have been selected for genome sequencing projects only during the last few years. This chapter provides an overview of the technologies involved and of the current status of genomic research with sulphate-reducing prokaryotes.