Dynamics of Biofilm Matrix Assembly in the Model Organism Pseudomonas Aeruginosa

Abstract

Bacteria form multicellular aggregates called biofilms. A crucial component of these aggregates is a protective matrix that holds the community together. Biofilm matrix composition varies depending upon bacterial species but typically includes exopolysaccharides (EPS), proteins, and extracellular DNA (eDNA). Pseudomonas aeruginosa, which is clinically important and also one of the model biofilm organisms, assembles aggregates using the structurally distinct EPS Psl and Pel, the matrix protein CdrA, and eDNA. Interestingly, both Psl and Pel localize to the periphery of aggregates. To examine how this peripheral localization occurs, we applied confocal laser scanning microscopy (CLSM) of live biofilms along with complementary biochemical and microbiological approaches to investigate three key variables: matrix degradation, production, and retention. We observed that biofilms retain matrix degrading enzymes, resulting in matrix components that are partially degraded without loss of biofilm biomass. These results suggest that matrix turnover is a normal aspect of biofilm physiology and does not necessarily precede biofilm aggregate disassembly as has been previously thought.