Bacteroides enzymes digest diatom alpha-mannan

• Applicant: Professor Dr. Jan-Hendrik Hehemann
• Subject Area: Microbial Ecology and Applied Microbiology
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 277249973

Biochemical and structural studies of enzymes that degrade algal polysaccharides are key to understand why certain glycans are more slowly digested and become a carbon dioxide sink in the ocean. Discoveries of putative alpha-mannan-degrading PULs in bloom-associated bacteria by the POMPU consortium partners, and our recently established purification of alpha-mannan from marine diatoms connect bacteria with diatoms in the carbon cycle. In the second phase of POMPU we have discovered hitherto unknown enzymes that initiate degradation of this alpha-mannan from diatoms. This is a particularly relevant process, since diatoms are responsible for about one quarter of earth’s photosynthesis. The respective enzymes are encoded in a polysaccharide utilization locus (PUL) that is common in marine Bacteroidetes thriving during diatom blooms. The focus of this proposal will be two endo-acting enzymes for which our preliminary experiments show that they initiate the mannan degradation cascade. We will investigate these endo-acting mannanases with the aim of obtaining biochemical specificity data and crystal structures in complex with fragments of the mannan substrate. Final aim will be to reconstruct the degradation cascade of alpha-mannan from diatoms, which will be crucial to uncover the role of diatom alpha-mannan for carbon dioxide cycling versus carbon dioxide sequestration.

• DFG Programme: Research Units
• Subproject of: FOR 2406: Proteogenomics of Marine Polysaccharide Utilization (POMPU)