Characterization of bacterial enzymes degrading sulfated polysaccharides from algae

Polysaccharides from diatoms form a large reservoir of organic carbon. This pool is generally seen as labile as it can undergo rapid consumption by marine heterotrophic bacteria. It also has been realized that anionic polysaccharides can escape rapid microbial degradation and form transparent exopolymeric particles that are strongly connected to aggregation of organic matter and subsequent sinking, which is known as the biological carbon pump. Hence we need to understand which and how polysaccharides can escape rapid microbial consumption and can actually form particles. There are several indications that diatoms produce complex sulfated heteropolysaccharides that could be semi-labile and have a low turnover rate. Such candidates are fucose containing sulfated polysaccharides (FCSP). As natural polysaccharides are in a heterogeneous mixture, analytical chemical methods cannot decipher their structure. But bacteria evolved carbohydrate active enzymes (CAZymes) containing active sides unique to monomeric motifs in polysaccharides. We want to deploy this enzymatic machinery to systematically depolymerise FCSP into smaller fragments that can be chemically analysed. Therefor our major aims are: i) Development of a CAZyme toolbox specific for FCSPs degradation. ii) Identification of the diatoms which produce FCSPs. iii) Measure whether FCSP are accumulating in the marine environment. In our recent work, we successfully cloned and expressed at least four enzymes acting as fucanases and we could provide a proof of concept that our CAZymes can be used to analyse FCSP