Emerging Roles of the Exopolysaccharide Matrix and Surface Sensing in Bacterial Communication and Ecology

Biofilms are surface-adhered, organized multicellular communities that are fundamental to the microbiology and ecology of bacteria. A canonical feature of bacterial biofilms is exopolysaccharides (EPS), which are secreted by bacteria during biofilm formation in response to increased c-di-GMP signaling. EPS molecules are known to function as cell-to-surface and cell-to-cell adhesins ('molecular glues'), and as structural components of the extracellular matrix. What is missing in microbiology is an understanding of precisely how EPS impacts bacterial surface sensing, signaling, intercellular communication, and motility behavior that ultimately lays the foundations of the bacterial biofilm, especially at a sufficient level of detail that allows deterministic engineering of bacterial social behavior. In our early work on Pseudomonas aeruginosa, the Psl EPS has been shown to be secreted on surfaces and act as trails for bacteria to follow during the initial stages of biofilm formation. At present, control of the exact structure, composition, and spatial location of bacterial EPS is an intractable problem, which makes it difficult to study how bacteria interact with their EPS at molecular resolution.