title: Influence of csgD and ompR on Nanomechanics, Adhesion Forces, and Curli Properties of E. coli.
abstract: Curli are bacterial appendages involved in the adhesion of cells to surfaces; their synthesis is regulated by many genes such as csgD and ompR. The expression of the two curli subunits (CsgA and CsgB) in Escherichia coli (E. coli) is regulated by CsgD; at the same time, csgD transcription is under the control of OmpR. Therefore, both genes are involved in the control of curli production. In this work, we elucidated the role of these genes in the nanomechanical and adhesive properties of E. coli MG1655 (a laboratory strain not expressing significant amount of curli) and its curli-producing mutants overexpressing OmpR and CsgD, employing atomic force microscopy (AFM). Nanomechanical analysis revealed that the expression of these genes gave origin to cells with a lower Young's modulus (E) and turgidity (P0), whereas the adhesion forces were unaffected when genes involved in curli formation were expressed. AFM was also employed to study the primary structure of the curli expressed through the freely jointed chain (FJC) model for polymers. CsgD increased the number of curli on the surface more than OmpR did, and the overexpression of both genes did not result in a greater number of curli. Neither of the genes had an impact on the structure (total length of the polymer and number and length of Kuhn segments) of the curli. Our results further suggest that, despite the widely assumed role of curli in cell adhesion, cell adhesion force is also dictated by surface properties because no relation between the number of curli expressed on the surface and cell adhesion was found.
authors.affiliation: Cardiff School of Pharmacy and Pharmaceutical Science, Cardiff University , Cardiff, U.K. CF10 3NB.
authors.forename: Stefano
authors.initials: S
authors.lastname: Perni
authors.affiliation: Cardiff School of Pharmacy and Pharmaceutical Science, Cardiff University , Cardiff, U.K. CF10 3NB.
authors.forename: Emily Callard
authors.initials: EC
authors.lastname: Preedy
authors.affiliation: Department of Biomolecular Sciences and Biotechnology, University of Milan , 20122 Milan, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Landini
authors.affiliation: Cardiff School of Pharmacy and Pharmaceutical Science, Cardiff University , Cardiff, U.K. CF10 3NB.
authors.forename: Polina
authors.initials: P
authors.lastname: Prokopovich
mesh_terms: D001422:Bacterial Adhesion / Q000502:physiology*; D001426:Bacterial Proteins / Q000378:metabolism*; D055119:Elastic Modulus; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C499694:CsgD protein, E coli; D029968:Escherichia coli Proteins; D015534:Trans-Activators; C112177:osmolarity response regulator proteins; C077481:Crl protein, Bacteria