Feast or friction? How marine polysaccharides shape bacterial life

Dr Jana Maßing
MARUM Center for Marine Environmental Sciences
Universität Bremen, Germany

Algae secrete megatons of complex glycans into the ocean. These compounds are considered a major carbon and energy source for heterotrophic microbes capable of degrading them using carbohydrateactive enzymes. However, this seems contradictory given the high abundance of these compounds, which remain largely resistant to microbial degradation.

For over 500 million years, these algae have evolved under constant microbial pressure in highly interconnected, permanently aqueous marine systems that promote microbial persistence and transmission - environments that have in the past facilitated some of the most severe human epidemics. To date, no adaptive immune mechanisms have been described in algae, highlighting the potential importance of alternative antimicrobial strategies.

We hypothesise that the secreted polysaccharide fucoidan is a broadly acting anti-pathogenic compound class involved in this evolutionary success. Hence what worked so well for algae for millions of years may also hold clues on how to develop glycan-based compounds to combat and evolutionary constrain human pathogens. Although, we are just beginning to explore the role of fucoidan our work, along with previous studies has shown strong effects of fucoidans on bacterial communities.

Our findings reveal that fucoidan functions as a biologically active matrix component that modulates bacterial physiology. Our results support the idea that complex cell-surface glycans can constrain microbial activity and suggest an unexpected mechanism by which algae may regulate microbial processes.