title: The Pseudomonas fluorescens SBW25 wrinkly spreader biofilm requires attachment factor, cellulose fibre and LPS interactions to maintain strength and integrity.
abstract: The wrinkly spreader (WS) isolate of Pseudomonas fluorescens SBW25 forms a substantial biofilm at the air-liquid interface. The biofilm is composed of an extracellular partially acetylated cellulose-fibre matrix, and previous mutagenesis of WS with mini-Tn5 had identified both the regulatory and cellulose-biosynthetic operons. One uncharacterized WS mutant, WS-5, still expressed cellulose but produced very weak biofilms. In this work, the mini-Tn5 insertion site in WS-5 has been identified as being immediately upstream of the tol-pal operon. Like Tol-Pal mutants of other Gram-negative bacteria, WS-5 showed a "leaky-membrane" phenotype, including the serendipitous ability to utilize sucrose, increased uptake of the hydrophilic dye propidium iodide, and the loss of lipopolysaccharide (LPS) expression. WS-5 cells were altered in relative hydrophobicity, and showed poorer recruitment and maintenance in the biofilm than WS. The WS-5 biofilm was also less sensitive to chemical interference during development. However, growth rate, cellulose expression and attachment were not significantly different between WS and WS-5. Finally, WS-5 biofilms could be partially complemented with WS-4, a biofilm- and attachment-deficient mutant that expressed LPS, resulting in a mixed biofilm with significantly increased strength. These findings show that a major component of the WS air-liquid biofilm strength results from the interactions between LPS and the cellulose matrix of the biofilm--and that in the WS biofilm, cellulose fibres, attachment factor and LPS are required for biofilm development, strength and integrity.
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Spiers
authors.affiliation: School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand.|Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK.
authors.forename: Paul B
authors.initials: PB
authors.lastname: Rainey
mesh_terms: D001422:Bacterial Adhesion / Q000235:genetics; D018441:Biofilms / Q000254:growth & development*; D002482:Cellulose / Q000096:biosynthesis / Q000378:metabolism*; D004251:DNA Transposable Elements; D005109:Extracellular Matrix / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial / Q000235:genetics; D005809:Genes, Regulator / Q000235:genetics; D008070:Lipopolysaccharides / Q000378:metabolism; D011551:Pseudomonas fluorescens / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D004251:DNA Transposable Elements; D008070:Lipopolysaccharides; D002482:Cellulose