Dueholm, Morten S.1; Søndergaard, Mads T2; Nilsson, Martin5; Christiansen, Gunna6; Stensballe, Allan7; Overgaard, Michael Toft2; Givskov, Michael Christian8; Tolker-Nielsen, Tim5; Otzen, Daniel E.1; Nielsen, Per H1
1 Department of Chemistry and Bioscience, The Faculty of Engineering and Science, Aalborg University, VBN2 Section of Biotechnology, The Faculty of Engineering and Science, Aalborg University, VBN3 The Faculty of Engineering and Science (ENG), Aalborg University, VBN4 EcoDesign, The Faculty of Engineering and Science, Aalborg University, VBN5 Department of Systems Biology6 Institut for Biomedicin - Medicinsk Mikrobiologi og Immunologi7 Department of Health Science and Technology, The Faculty of Medicine, Aalborg University, VBN8 Department of Microbiology
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.
Microbiologyopen, 2013, Vol 2, Issue 3, p. 365-382