MARUM Research Academy

Degradation of the marine red algal polysaccharide carrageenan by human gut bacteria

Algal polysaccharides in the marine environment provide carbon for microbes that can scavenge these molecules with specialized protein pathways. These polysaccharide degradation pathways are often not restricted to one ecosystem but rather exchanged via horizontal gene transfer. This allows bacteria from different environments to expand their ability to consume new polysaccharides. Human gut bacteria have similarly evolved by gene transfer to degrade marine algal polysaccharides such as porphyran, agar and alginate. Another red algal polysaccharide ‘Carrageenan’ is a relatively recent addition in the Westerner’s diet. It is used extensively by the food industry as an emulsifying agent but it remained unknown whether the gut bacteria could metabolize this polysaccharide.

My PhD project focuses on a human gut bacterium that has evolved to specifically capture, catabolize and consume carrageenan using a multi-protein membrane system. Since this degradation pathway stems from marine bacteria, the biochemical and microbial mechanism of carrageenan degradation in the gut ecosystem contributes to the understanding of organic matter degradation in the sea.