K-048. Phenazine Production Influences Biofilm Initiation and Development in Pseudomonas Aeruginosa PA14

I. Ramos-Solis, L. Dietrich, D. Newman;
Massachusetts Inst. of Technology, Cambridge, MA.

Microorganisms produce a great variety of small compounds and although many of them have been found to have antibiotic properties, the physiological roles of these compounds are potentially as diverse as their chemical structures. Bacteria of the genus Pseudomonas are known for their ability to produce phenazines. In our laboratory it has been shown that phenazines, despite being called secondary metabolites for their supposed dispensability, are actively involved in the physiology of their producers. Recently, the role of these compounds as regulators of the expression of a limited set of genes has been uncovered. In this study we show that phenazines play an important role in biofilm development, affecting morphology of Pseudomonas aeruginosa multicellular communities. While attachment to surfaces followed by a decrease in cell motility are phenotypes associated with biofilm-producing strains, a phenazine defective mutant (Δphz) displays increased swarming motility and decreased irreversible attachment to polystyrene and glass surfaces, relative to the wild-type. Biofilm morphology was also altered in the Δphz mutant. When grown on agar plates, the Δphz mutant forms rough and dry colony biofilms that occupy a larger surface area in contrast to the smoother and smaller colonies formed by the wild-type. Similarly, in a flow-cell system, depending upon nutritional conditions, the Δphz mutant grows into large unstructured cell aggregates as opposed to the round highly-defined wild-type microcolonies. These results show that small molecules such as phenazines can impact biofilm development at different levels, probably by regulating cellular differentiation into efficient biofilm forming cells and/or by participating actively in the maintenance of the multicellular community.