Bacterial utilization of anionic polysaccharides from macroalgae

Abstract

About two thirds of Earth is covered by oceans of which less than 2 % constitute marine vegetation. Yet, marine vegetation serves crucial ecosystem functioning and is especially vital to the health of coastal ecosystems. Macroalgae display one group of marine vegetation which can form ecological habitats that are not only impressive by their dimensions but also with regards to biodiversity and primary production. Among algal compounds, polysaccharides play an important role as bioactive polymers and food source for heterotrophic organisms. Especially anionic polysaccharides are of high scientific interest as they define the 3D structure of the algae and sequester carbon in form of sinking particles from the photic zone to the deep sea. Detailed insights into the enzymatic machinery of heterotrophic bacteria capable to utilize algal polysaccharides contributes to a better understanding of carbon cycling and food web dynamics in the marine environment. In the present dissertation, I investigated different aspects of bacterial utilization of three anionic polysaccharides from macroalgae – ulvan, alginate and fucoidan. The research in the present dissertation delivered molecular insights into the function and structure of glycan-degrading enzymes. These findings will contribute to a greater understanding of the utilization of anionic polysaccharides by marine heterotrophic bacteria. Consequently, using bacterial enzymes as analytical tools to investigate the turnover rates of anionic polysaccharides will elucidate their fate in the marine carbon cycle.