The matrix is a defining feature of biofilms and supports the formation of structures that enhance access to oxygen in difterent biofilm models. Using pseudomonas aeruginosa of matrix to in-biofilm eculogy and evolvability. Pel polysaccharide is a critical maxtrix component in pellicle (air-liquid in ferface)and colony (solid-surface) biofilms. Pel production could be exhunced. Pel production that were disfavored in colonies but not in pellioles. Pellicles favored spontaneous mutants with enhanced.