The pel polysaccharide can serve a structural and protective role in the biofilm matrix of Pseudomonas aeruginosa

• Published in: PLoS pathogens Vol. 7; no. 1; p. e1001264
• Main Authors: Colvin, Kelly M, Gordon, Vernita D, Murakami, Keiji, Borlee, Bradley R, Wozniak, Daniel J, Wong, Gerard C L, Parsek, Matthew R
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01-01-2011; Public Library of Science (PLoS)
• Subjects: Alginates; Anti-Bacterial Agents - pharmacology; Antimicrobial agents; Bacterial Adhesion; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Biofilms; Biofilms - growth & development; Experiments; Extracellular Matrix - physiology; Gene Expression Regulation, Bacterial; Genetic aspects; Microbial mats; Microbial polysaccharides; Microbial Sensitivity Tests; Microbial Viability - drug effects; Microbiology; Microbiology/Medical Microbiology; Microbiology/Microbial Growth and Development; Operons; Physiological aspects; Polysaccharides, Bacterial - genetics; Polysaccharides, Bacterial - metabolism; Pseudomonas aeruginosa; Pseudomonas aeruginosa - drug effects; Pseudomonas aeruginosa - growth & development; Pseudomonas aeruginosa - physiology; Tobramycin - pharmacology
• ISSN: 1553-7374; 1553-7366; 1553-7374
• DOI: 10.1371/journal.ppat.1001264

Bacterial extracellular polysaccharides are a key constituent of the extracellular matrix material of biofilms. Pseudomonas aeruginosa is a model organism for biofilm studies and produces three extracellular polysaccharides that have been implicated in biofilm development, alginate, Psl and Pel. Significant work has been conducted on the roles of alginate and Psl in biofilm development, however we know little regarding Pel. In this study, we demonstrate that Pel can serve two functions in biofilms. Using a novel assay involving optical tweezers, we demonstrate that Pel is crucial for maintaining cell-to-cell interactions in a PA14 biofilm, serving as a primary structural scaffold for the community. Deletion of pelB resulted in a severe biofilm deficiency. Interestingly, this effect is strain-specific. Loss of Pel production in the laboratory strain PAO1 resulted in no difference in attachment or biofilm development; instead Psl proved to be the primary structural polysaccharide for biofilm maturity. Furthermore, we demonstrate that Pel plays a second role by enhancing resistance to aminoglycoside antibiotics. This protection occurs only in biofilm populations. We show that expression of the pel gene cluster and PelF protein levels are enhanced during biofilm growth compared to liquid cultures. Thus, we propose that Pel is capable of playing both a structural and a protective role in P. aeruginosa biofilms.