Diversity and Ecology of Marine Planctomycetes

Abstract

Planctomycetes are widely distributed in terrestrial and aquatic habitats, but little is known about their detailed physiology. Recently, a group of Planctomycetes were discovered, which anaerobically oxidizes ammonium to dinitrogen gas - the anammox bacteria. The anammox process was shown to play an important role in the loss of fixed nitrogen in marine oxygen minimum zones (OMZs). In this thesis, the particle association of anammox bacteria in the Namibian OMZ was investigated, as well as the co-occurring microbial community and their potential contribution to the anammox process. Furthermore, the diversity of marine anammox bacteria was studied by a comparative analysis of 16S rRNA gene sequences and 16S-23S rRNA intergenic spacer regions (ITS). A greater microdiversity than previously assumed was observed and a new cluster of a novel anammox species was found, for which the name Candidatus Scalindua arabica is proposed. To investigate the metabolic potential of chemoorganoheterotrophic planctomycetes, five fosmids generated from marine samples and related to so far uncultured planctomycetes were sequenced, annotated and compared with all available planctomycete genomes.