Diversität nitratreduzierender Bakteriengemeinschaften in den Sedimenten der Ostsee und Untersuchungen zur Phylogenie der respiratorischen Nitratreduktase.

On the basis of available nitrate reductase gene sequences primer pairs were designed to specifically amplify gene stretches of the b-subunit of the membrane-bound nitrate reductase (narH) and applied to DNA from new isolates and reference species as well as environmental DNA. According to phylogenetic calculations the respiratory nitrate reduction is one of the most original physiological functions of prokaryotic life, which was already present in the "urkaryotes" together with other respiratory functions like sulfate reduction. The highly congruent evolution of the 16S rDNA and narH allows the phylogenetic classification of sequences from environmental DNA. Based on these group-specific primers nitrate-reducing bacterial communities from Baltic Sea sediments were investigated with various molecular techniques. Numerous bands could be extracted from DG-DGGE gels, sequenced and classified within the phylogenetic tree of reference sequences. In addition to the molecular analysis of the Baltic Sea sediment communities nitrate reducing bacteria from environmental samples were isolated and physiologically investigated. Both approaches revealed large differences between the various sampling stations which were discussed due to chemical and physical conditions. The shallow water sediments from the sampling stations "westliche Ostsee" and "finnischer Meerbusen" showed a strong coupling of nitrification and denitrification processes within the uppermost sediment layers which could be inferred from diversity analysis as well. The "sulfidic" sampling stations at deep basins within the central Baltic Sea revealed a competition of nitrate reducers and sulfate reducers on organic material which led to a strong stratification of the bacterial diversity.