PLANT POLYSACCHARIDES AS CARDINAL DETERMINANTS OF ROOT-ASSOCIATED BIOFILM DEVELOPMENT

The natural habitat of Bacillus subtilis is the soil, where it forms complex multicellular communities termed biofilms on plant roots and resides within the root’s rhizosphere. Bacillus biofilms play a beneficial role in maintaining the optimal rhizosphere environment, which supports plant growth and protects it from fungal and bacterial pathogens. One key question in the interaction between B. subtilis and plant roots is the mechanisms by which Bacillus subtilis adapts to its host. We suggest that the colonization leading to a successful interaction can be facilitated by plant polysaccharides. Thus, we study the metabolism of root polysaccharides and their possible regulatory effect on gene expression and gene acquisition of B. subtilis. Our work demonstrates that plant polysaccharides can serve as a secondary carbon source as well as signals that activate highly specific biofilm signalling pathways for each plant polysaccharide independently. These bacterial responses then allow B. subtilis to respond to various plant cell wall polysaccharides from neighbouring roots or roots of different ages, leading to a beneficial interaction between B. subtilis and plant roots.