The large square image is a horizontal view of the biofilm, and the rectangular image is a side view of the biofilm. A representative biofilm image for each sample is shown. The biofilm thickness of each sample was calculated by averaging the maximum thicknesses of the nine image stacks. For each strain, biofilm images were obtained for nine areas covering 2.0 × 10 5 μm 2 along the flow cell. The images of the biofilms that formed on the glass coverslips were acquired by CLSM after 22 and 66 h under flow conditions. These values were normalized to the results for PAO1 ( A 540, 0.295). The values at the top (0 h) indicate the initial attachment values obtained in a 1-h attachment microtiter dish assay of the cultures used in the flow cells. After 1 h of incubation without flow to allow the cells to attach, a continuous flow of Jensen's medium was started. Cultures of each strain were grown in Jensen's medium (OD 600, ∼0.5) with or without arabinose and were injected into a flow cell device. Biofilms of PAO1, WFPA800 (Δ psl), and WFPA801 (Δ psl/p BAD- psl) were analyzed in a continuous-culture flow cell system. Psl contributes to biofilm formation and structure following initial attachment. aeruginosa adhesion, which is critical for initiation and maintenance of the biofilm structure.

We propose that Psl has an important role in P. This translated into significant changes in the architecture of the biofilm. Overproduction of the Psl polysaccharide led to enhanced cell-surface and intercellular adhesion of P. Analysis of biofilms formed by the Deltapsl/p(BAD)-psl strain indicated that expression of the psl operon is required to maintain the biofilm structure at steps postattachment. aeruginosa strain (Deltapsl/p(BAD)-psl) by replacing the psl promoter region with araC-p(BAD), so that expression of psl could be controlled by addition of arabinose. To study the potential roles of Psl apart from attachment, we generated a psl-inducible P. Our results showed that psl is required for attachment to a variety of surfaces, independent of the carbon source. In this study, we investigated the adherence properties of this DeltapslAB mutant using biotic surfaces (epithelial cells and mucin-coated surfaces) and abiotic surfaces. aeruginosa PAO1 strain with disruption of pslA and pslB (DeltapslAB) was severely compromised, indicating that psl has a role in cell-surface interactions. The 15-gene psl operon encodes a putative polysaccharide that plays an important role in biofilm initiation in nonmucoid P. The ability to form biofilms in the airways of people suffering from cystic fibrosis is a critical element of Pseudomonas aeruginosa pathogenesis.

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