title: A chemosensory system that regulates biofilm formation through modulation of cyclic diguanylate levels.
abstract: Pseudomonas aeruginosa causes chronic biofilm infections, and its ability to attach to surfaces and other cells is important for biofilm formation and maintenance. Mutations in a gene called wspF, part of a putative chemosensory signal-transduction operon, have been shown to result in cell aggregation and altered colony morphology. The WspF phenotypes depend on the presence of WspR, which is a member of a family of signal transduction proteins known as response regulators. It is likely that the effect of the wspF mutation is to cause constitutive activation of WspR by phosphorylation. WspR contains a GGDEF domain known to catalyze formation of a cytoplasmic signaling molecule cyclic diguanylate (c-diGMP). We determined that purified WspR catalyzed the formation of c-diGMP in vitro and phosphorylation stimulated this activity. We observed increased cellular levels of c-diGMP and increased biofilm formation in a wspF mutant. Expression of a protein predicted to catalyze degradation of c-diGMP reversed the phenotypes of a wspF mutant and inhibited biofilm initiation by wild-type cells, indicating that the presence of c-diGMP is necessary for biofilm formation. A transcriptome analysis showed that expression levels of at least 560 genes were affected by a wspF deletion. The psl and pel operons, which are involved in exopolysaccharide production and biofilm formation, were expressed at high levels in a wspF mutant. Together, the data suggest that the wsp signal transduction pathway regulates biofilm formation through modulation of cyclic diguanylate levels.
authors.affiliation: Department of Microbiology, Box 357242, University of Washington, 1959 Northeast Pacific Street, Seattle, WA 98195, USA.
authors.forename: Jason W
authors.initials: JW
authors.lastname: Hickman
authors.forename: Delia F
authors.initials: DF
authors.lastname: Tifrea
authors.forename: Caroline S
authors.initials: CS
authors.lastname: Harwood
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development*; D002855:Chromatography, Thin Layer; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D049452:Green Fluorescent Proteins; D018613:Microscopy, Confocal; D016296:Mutagenesis; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D049452:Green Fluorescent Proteins; C062025:bis(3',5')-cyclic diguanylic acid; D006152:Cyclic GMP