Petri, Ralf (2000) Diversität nitratreduzierender Bakteriengemeinschaften in den Sedimenten der Ostsee und Untersuchungen zur Phylogenie der respiratorischen Nitratreduktase. (PhD/ Doctoral thesis), Christian-Albrechts-Universität zu Kiel, Kiel, Germany, 161 pp.

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Abstract

On the basis of available nitrate reductase gene sequences primer pairs were designed to specifically amplify gene stretches of the -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. Since the proteins for nitrate reduction (NarH) and nitrite oxidation (NorB), which may have evolved from one common progenitor, are highly orthologous within bacterial and archaeal species the primer systems can be used for phylogenetic and diversity analysis of both functional groups, nitrate reducers and nitrite oxidizers. Analysis of communities from Baltic Sea sediments revealed information about the diversity and the interactions of the environmental community. Numerous bands could be extracted from DG-DGGE gels, sequenced and classified within the phylogenetic tree of reference sequences. None of the bands could be identified by comparison to sequences from reference organisms but many of them could be ordered to taxonomic groups like proteobacteria or Gram-positive bacteria. The molecular analysis of the Baltic Sea sediments was completed with results from isolation of nitrate reducing bacteria from environmental samples. Both techniques revealed large differences between the various sampling stations which could be 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 iversity.

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