Extracellular matrix chemistry tunes bacterial biofilm metabolism and optimizes fitness

Chemically complex extracellular matrices define cellular microenvironments and shape cell behavior. We hypothesized a composition--properties--function relationship in these natural living materials, where interactions among matrix components govern material properties and cellular physiology. Using Pseudomonas aeruginosa biofilms as a model system, we show that electrostatic interactions between the cationic polysaccharide Pel and extracellular DNA (eDNA) regulate retention of pyocyanin (PYO), a redox-active metabolite that supports anaerobic metabolism via extracellular electron transfer (EET). Biofilm-mimetic hydrogels and natural biofilms revealed that altering Pels charge via pH adjustment or chemical acetylation, or tuning the Pel:eDNA ratio, predictably modulates PYO retention and EET efficiency. Functionally, a lower Pel:eDNA ratio enhances metabolism under oxygen limitation, whereas a higher ratio promotes survival under antibiotic stress. These findings highlight how matrix chemistry encodes tunable material properties that confer biofilm fitness advantages and establish a materials-based framework for understanding extracellular matrices in multicellular communities.