Roseobacter

Roseobacter

Representatives of the Roseobacter group are the most common prokaryotes in marine ecosystems. These bacteria are physiologically very versatile and play an important role in global marine biogeochemical cycles. The TRR 51 aims at understanding the evolutionary, genetic and physiological principles which are the foundation of payoff of these bacteria. To achieve this the Roseobacter group is investigated starting from the ecosystem to the system biology of model organisms respective to the major biogeochemical and metabolic processes and their genetic and genomic basics.

Summary

The overarching goal of this Transregional Collaborative Research Centre (CRC) TRR 51 “Roseobacter” is a
comprehensive understanding of the evolutionary and adaptational success of the Roseobacter group in
marine ecosystems.

Representatives of this group are also characterized by very different and versatile physiologies. The mission of TRR51 is to study the Roseobacter group in terms of evolution and phylogeny and the structure and content of the genomes in terms of their versatile physiology and ecology. These studies include environmental and biogeographical studies at the Community level, as well as detailed work on the physiology of individual organisms and systems biology studies of two model organisms, Dinoroseobacter shibae and Phaeobacter inhibbens DSM 17395. The investigations in the third application phase will focus on interactions of these organisms, mainly with two algae from coastal seas,  the cosmopolitan coastal diatom Thalassiosira rotula and Prorocentrum minimum, a cosmopolitan toxic dinoflagellate. Furthermore, interactions with and the importance of phages are another focus of investigation.

The work is still divided into project area A with a focus on ecology and evolution, project area B with a focus on genetics and physiology and project area C with a focus on the systems biology of the two model organisms.

The environmental studies, mainly located in Project Area A, will complete the analyses of the samples and data collected during two voyages with the research vessel Sonne in the Pacific Ocean on a transect along the 180th longitude between the water masses of the southern polar front at 52°S and subarctic areas in the Bering Sea at 59°N. The work included sampling of the water column and surface sediment for measurements of the activity and composition of bacterial communities, metagenomic, transcriptomic, proteomic and geometabolomic studies. These investigations aim at a comprehensive and synoptic analysis of these data together with data from previous voyages in the Atlantic and Southern Ocean to establish a synoptic prediction model of the functional role of pelagic and benthic Roseobacter representatives.

Studies with the model organisms D. shibae and P. inhibens, native to all three project areas, focus on interactions with the two model algae T. rotula and P. minimum. The genomes of both algae will be sequenced. Topics include the influence of the interactions on the endo- and exometabolomes of both partners, the role of specific metabolites on algal growth, the role of quorum sensing, oxygen partial pressure, iron and temperature on growth regulation and metabolite exchange, and the importance of extrachromosomal elements. The different effects of direct physical interactions and interactions mediated only by solute exchange are specifically studied. Transcriptional and proteomic approaches will be used in most of the planned studies, as well as the modelling of the metabolic interactions of both partners.