Rhodopirellula baltica belongs to the deep branching phylum Planctomycetes and is of scientific interest for several reasons: due to its abundance and carbohydrate metabolism, it is regarded as environmentally relevant among marine microbes; it displays morphological peculiarities (peptidoglycan-free proteinaceous cell wall, intracellular compartmentalization, cell cycle due to reproduction via budding).

Research emphasis was the following:

• taxonomic re-examination of the planctomycetes and description Rhodopirellula baltica;

• establishment of cultivation in defined mineral media as basis for subsequent functional studies

• establishment of the first 2-DE reference map (558 non-redundant proteins) as framework for further experiments. In total, 146 proteins contained a predicted signal peptide suggesting their translocation out of the intracellular compartment, the pirellulosome;

• catabolic protein signatures of R. baltica cultures adapted to aerobic growth with eight different carbohydrates. Almost all enzymes of glycolysis and TCA cycle were identified and showed very stable protein abundances across all test conditions. Most of the substrate specifically regulated proteins were either dehydrogenases/oxidoreductases or proteins of unknown function which are unique for R. baltica. Results suggest novel reactions/enzymes for carbohydrate breakdown.

• investigations on growth phase-dependent changes of the protein composition revealed several candidates possibly involved in the development of R. baltica morphotypes (swarmer versus attached cells). In addition, first insights were obtained in the protein signature characterizing transition into stationary phase.

Collaborations:

DSMZ Braunschweig (B.J. Tindall), MPI Bremen (R. Amann, F.O. Glöckner), MPI Berlin (J. Gobom, R. Reinhardt), University Kiel (H. Schlesner)