Exploiting Enzymatic Machineries of Bacteria to Resolve Marine Polysaccharide Turnover

• Applicant: Professor Dr. Jan-Hendrik Hehemann
• Subject Area: Microbial Ecology and Applied Microbiology ; Biochemistry
• Term: from 2014 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 259266681

The goal of this research project is to (i) characterize the proteomic machinery used by marine microbes to consume algal polysaccharides and develop and apply this set of well characterized CAZymes for the rational and durable analysis of algal polysaccharide mixture, analogous to the use of restriction enzymes in analyzing DNA, and (ii) use these enzymes as diagnostic tools to measure turnover of algal polysaccharides in seawater. The mechanistic data derived from this established approach - transferred to marine systems - will serve to clarify kinetics of turnover of algal glycans by bacteria and shed light on this black box of the marine carbon cycle.Algal polysaccharides are the most abundant carbon and energy resource in marine systems. Their widely recognized relevance stands in stark contrast to the lack of available tools that allow measuring and identifying distinguished types of polysaccharides in seawater. Glycans have heterogeneous structures and occur as mixtures in nature, hindering their purification from seawater and identification with spectroscopic methods. Thus, it remains challenging to establish the kinetics of marine glycan turnover.The work proposed here recognizes that marine bacteria use specific enzymes to resolve the structures of algal polysaccharides. Bacteria degrade and catabolize polysaccharides with carbohydrate active enzymes (CAZymes) that have active sites adapted to unique monomer sequences. This molecular recognition is key for efficient bacterial catabolism of algal glycans. This "key lock" recognition is also the key criterion for our use of CAZymes as diagnostic tools to reveal algal carbohydrates in seawater in the following manner: CAZymes that degrade select algal glycans (mannans, beta-glucans), will be characterized. These CAZymes can then be used to hydrolyze mannans and beta-glucans from microalgae. This enzymatic splitting creates products (oligo- and monosaccharides), which we can measure with standard chemical assays to establish the quantity of the respective polymeric glycan in the seawater sample. Thus, with CAZymes it is here proposed to measure the production of select polysaccharides i.e. during algal blooms and to establish their degradation rates by bacterial communities. Our data will help to instruct models reconstructing turnover of carbohydrates of the "Sweet Ocean" - the largest, most dynamic, yet least understood carbon pool on earth.

• DFG Programme: Independent Junior Research Groups