title: Self-produced exopolysaccharide is a signal that stimulates biofilm formation in Pseudomonas aeruginosa.
abstract: Bacteria have a tendency to attach to surfaces and grow as structured communities called biofilms. Chronic biofilm infections are a problem because they tend to resist antibiotic treatment and are difficult to eradicate. Bacterial biofilms have an extracellular matrix that is usually composed of a mixture of polysaccharides, proteins, and nucleic acids. This matrix has long been assumed to play a passive structural and protective role for resident biofilm cells. Here we show that this view is an oversimplification and that the biofilm matrix can play an active role in stimulating its own synthesis. Working with the model biofilm bacterium Pseudomonas aeruginosa, we found that Psl, a major biofilm matrix polysaccharide for this species, acts as a signal to stimulate two diguanylate cyclases, SiaD and SadC, to produce the intracellular secondary messenger molecule c-di-GMP. Elevated intracellular concentrations of c-di-GMP then lead to the increased production of Psl and other components of the biofilm. This mechanism represents a unique positive feedback regulatory circuit, where the expression of an extracellular polysaccharide promotes biofilm growth in a manner analogous to autocrine signaling in eukaryotes.
authors.affiliation: Department of Microbiology, University of Washington, Seattle, WA 98195, USA.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Irie
authors.forename: Bradley R
authors.initials: BR
authors.lastname: Borlee
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: O'Connor
authors.forename: Preston J
authors.initials: PJ
authors.lastname: Hill
authors.forename: Caroline S
authors.initials: CS
authors.lastname: Harwood
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Wozniak
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Parsek
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D018441:Biofilms / Q000254:growth & development*; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D005109:Extracellular Matrix / Q000502:physiology; D025461:Feedback, Physiological; D005798:Genes, Bacterial; D019761:Phosphorus-Oxygen Lyases / Q000235:genetics / Q000378:metabolism; D011135:Polysaccharides, Bacterial / Q000502:physiology*; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000502:physiology*; D015290:Second Messenger Systems; D015398:Signal Transduction
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D011135:Polysaccharides, Bacterial; C064841:exopolysaccharide, Pseudomonas; C062025:bis(3',5')-cyclic diguanylic acid; D019761:Phosphorus-Oxygen Lyases; C060720:diguanylate cyclase; D006152:Cyclic GMP