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Stefan Becker

Institution:University of Bremen
Room:MARUM Pavillon, room 0040
Phone:+49 421 218 - 65752
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Other webpage(s):Stefan's MARUM web page
Stefan Becker

PhD project:

Beta-glucan recycling by marine microbes

One of the most abundant marine carbon and energy sources are algal polysaccharides. However, due to their heterogeneous structures and because their occurrence as mixtures in nature, the quantification and qualification of the different types of polysaccharides in seawater lacks suitable tools for their measurement.

Marine bacteria are able to catabolize algal polysaccharides by using specific carbohydrate active enzymes (CAZymes), which is why these enzymes can also be used as diagnostic tools to analyze algal polysaccharides in seawater. CAZymes hydrolyze polysaccharides and the created oligo- and monosaccharides can be quantified afterwards. This information is used to draw conclusions from the production of polysaccharides during algal blooms and their degradation by bacteria.

In order to analyze a mixture of algal polysaccharides we need a set of well-characterized CAZymes, so the first step of this PhD project focuses the synthetization and characterization of the ecological relevant laminarin polysaccharide utilization loci (PUL) of Formosa agaraphila. This includes cloning, isolation and characterization of these proteins via both structural enzymology and activity screenings. Through mutagenesis we will additionally investigate the importance of residues identified by the structural studies as participating in the affinity and specificity of the interactions. In the second step we then want to apply this tool box of enzymes towards a quantification of laminarin turnover in seawater. First we want to test the setup in a lab experiment and afterwards apply this setup to natural environments.

Eventually we will have a mechanistic and quantitative understanding how bacteria catabolize laminarin in the environment. For the future we will have established a framework that can be extended towards the marine catabolism of other complex carbon resources.

Thesis committee:

Dr. Jan-Hendrik HehemannUniversity of Bremen
Prof. Carol ArnostiUniversity of North Carolina at Chapel Hill, USA
Prof. Dr. Thorsten DittmarUniversity of Oldenburg
Dr. Bernhard FuchsMax Planck Institute for Marine Microbiology, Bremen