title: Expression of Fap amyloids in Pseudomonas aeruginosa, P. fluorescens, and P. putida results in aggregation and increased biofilm formation.
abstract: The fap operon, encoding functional amyloids in Pseudomonas (Fap), is present in most pseudomonads, but so far the expression and importance for biofilm formation has only been investigated for P. fluorescens strain UK4. In this study, we demonstrate the capacity of P. aeruginosa PAO1, P. fluorescens Pf-5, and P. putida F1 to express Fap fibrils, and investigated the effect of Fap expression on aggregation and biofilm formation. The fap operon in all three Pseudomonas species conferred the ability to express Fap fibrils as shown using a recombinant approach. This Fap overexpression consistently resulted in highly aggregative phenotypes and in increased biofilm formation. Detailed biophysical investigations of purified fibrils confirmed FapC as the main fibril monomer and supported the role of FapB as a minor, nucleating constituent as also indicated by bioinformatic analysis. Bioinformatics analysis suggested FapF and FapD as a potential β-barrel membrane pore and protease, respectively. Manipulation of the fap operon showed that FapA affects monomer composition of the final amyloid fibril, and that FapB is an amyloid protein, probably a nucleator for FapC polymerization. Our study highlights the fap operon as a molecular machine for functional amyloid formation.
authors.affiliation: Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Aalborg, Denmark.
authors.forename: Morten S
authors.initials: MS
authors.lastname: Dueholm
authors.forename: Mads T
authors.initials: MT
authors.lastname: Søndergaard
authors.forename: Martin
authors.initials: M
authors.lastname: Nilsson
authors.forename: Gunna
authors.initials: G
authors.lastname: Christiansen
authors.forename: Allan
authors.initials: A
authors.lastname: Stensballe
authors.forename: Michael T
authors.initials: MT
authors.lastname: Overgaard
authors.forename: Michael
authors.initials: M
authors.lastname: Givskov
authors.forename: Tim
authors.initials: T
authors.lastname: Tolker-Nielsen
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Otzen
authors.forename: Per H
authors.initials: PH
authors.lastname: Nielsen
mesh_terms: D000682:Amyloid / Q000235:genetics / Q000378:metabolism*; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development*; D019295:Computational Biology; D009876:Operon; D055503:Protein Multimerization; D011550:Pseudomonas aeruginosa / Q000378:metabolism / Q000502:physiology*; D011551:Pseudomonas fluorescens / Q000378:metabolism / Q000502:physiology*; D016958:Pseudomonas putida / Q000378:metabolism / Q000502:physiology*
chemical_list: D000682:Amyloid; D001426:Bacterial Proteins