Genes involved in matrix formation in Pseudomonas aeruginosa PA14 biofilms

Abstract

SummaryPseudomonas aeruginosa forms diverse matrixenclosed surface-associated multicellular assemblages (biofilms) that aid in its survival in a variety of environments. One such biofilm is the pellicle that forms at the air-liquid interface in standing cultures. We screened for transposon insertion mutants of P. aeruginosa PA14 that were unable to form pellicles. Analysis of these mutants led to the identification of seven adjacent genes, named pel genes, the products of which appear to be involved in the formation of the pellicle's extracellular matrix. In addition to being required for pellicle formation, the pel genes are also required for the formation of solid surface-associated biofilms. Sequence analyses predicted that three pel genes encode transmembrane proteins and that five pel genes have functional homologues involved in carbohydrate processing. Microscopic and macroscopic observations revealed that wild-type P. aeruginosa PA14 produces a cellulase-sensitive extracellular matrix able to bind Congo red; no extracellular matrix was produced by the pel mutants. A comparison of the carbohydrates produced by the wild-type strain and pel mutants suggested that glucose was a principal component of the matrix material. Together, these results suggest that the pel genes are responsible for the production of a glucose-rich matrix material required for the formation of biofilms by P. aeruginosa PA14.

Genetic determinants of biofilm development of opaque and translucent Vibrio parahaemolyticus

“…As a result, this screen has enabled identification of biofilm determinants that we might not have detected using the crystal violet assay. Consistent with our findings in V. parahaemolyticus, a pellicle screen was recently implemented in Pseudomonas aeruginosa PA14 to discover new genetic determinants involved in the production of a carbohydrate containing extracellular matrix component (Friedman and Kolter, 2004).…”

“…This medium has been used to detect cell surface appendages, extracellular matrix production, A- layer proteins, and as an indicator of virulence (Kay et al, 1985;Collinson et al, 1993;Romling and Rohde, 1999;Romling et al, 2000;Zogaj et al, 2003;Friedman and Kolter, 2004). OP or TR parental strains have rough colony morphologies when grown on Congo red medium (Fig.…”

Calcium-Induced Virulence Factors Associated with the Extracellular Matrix of MucoidPseudomonas aeruginosaBiofilms

“…Similar results were obtained using a mutant derivative of the nonmucoid strain P. aeruginosa PAO1 engineered to overproduce alginate (25,60). On the other hand, results using wild-type P. aeruginosa PAO1 and PA14 showed that alginate was not associated with biofilms (72) and that a second polysaccharide likely encoded by a separate polysaccharide biosynthetic gene cluster may provide the extracellular matrix material for those cells (18,19,29). In another report, using P. aeruginosa PAO1, DNA was suggested to be the extracellular matrix material, since the addition of DNase to biofilms dispersed the bacteria (64).…”

High-Resolution Visualization ofPseudomonas aeruginosaPAO1 Biofilms by Freeze-Substitution Transmission Electron Microscopy

“…A recent study describing the EPS of PAO1 biofilms identified the major carbohydrate moieties in this to include glucose, rhamnose, mannose, xylose, 3-deoxy-D-manno-oct-2-ulosonic acid (KDO),N-acetylgalactosamine, N-acetylfucosamine, and N-acetylglucosamine (70). More recently, two genetic loci (psl and pel) responsible for the production of mannose-rich (psl) and glucose-rich (pel) polymer components of P. aeruginosa EPS (18,19,52) were identified. With the exception of KDO with its ionizable carboxylate, most of the sugars described in these studies are neutrally charged or sugars with a possible ionizable amine group (depending on polymeric linkage), which may be difficult to stain.…”