title: Conformation change in a self-recognizing autotransporter modulates bacterial cell-cell interaction.
abstract: Bacteria mostly live as multicellular communities, although they are unicellular organisms, yet the mechanisms that tie individual bacteria together are often poorly understood. The adhesin involved in diffuse adherence (AIDA-I) is an adhesin of diarrheagenic Escherichia coli strains. AIDA-I also mediates bacterial auto-aggregation and biofilm formation and thus could be important for the organization of communities of pathogens. Using purified protein and whole bacteria, we provide direct evidence that AIDA-I promotes auto-aggregation by interacting with itself. Using various biophysical and biochemical techniques, we observed a conformational change in the protein during AIDA-AIDA interactions, strengthening the notion that this is a highly specific interaction. The self-association of AIDA-I is of high affinity but can be modulated by sodium chloride. We observe that a bile salt, sodium deoxycholate, also prevents AIDA-I oligomerization and bacterial auto-aggregation. Thus, we propose that AIDA-I, and most likely other similar autotransporters such as antigen 43 (Ag43) and TibA, organize bacterial communities of pathogens through a self-recognition mechanism that is sensitive to the environment. This could permit bacteria to switch between multicellular and unicellular lifestyles to complete their infection.
authors.affiliation: Canada Research Chair on Bacterial Animal Diseases, Université de Montréal, Saint-Hyacinthe, Québec J2S 7C6, Canaada.
authors.forename: Victoria
authors.initials: V
authors.lastname: Girard
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Côté
authors.forename: Marie-Eve
authors.initials: ME
authors.lastname: Charbonneau
authors.forename: Manuel
authors.initials: M
authors.lastname: Campos
authors.forename: Frédéric
authors.initials: F
authors.lastname: Berthiaume
authors.forename: Mark A
authors.initials: MA
authors.lastname: Hancock
authors.forename: Nadeem
authors.initials: N
authors.lastname: Siddiqui
authors.forename: Michael
authors.initials: M
authors.lastname: Mourez
mesh_terms: D018830:Adhesins, Escherichia coli / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D001422:Bacterial Adhesion / Q000187:drug effects / Q000502:physiology*; D003432:Cross-Linking Reagents / Q000494:pharmacology; D003840:Deoxycholic Acid / Q000494:pharmacology; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D008968:Molecular Conformation; D055503:Protein Multimerization; D012965:Sodium Chloride / Q000494:pharmacology; D020349:Surface Plasmon Resonance
chemical_list: C075559:AIDA-I protein, E coli; D018830:Adhesins, Escherichia coli; D003432:Cross-Linking Reagents; D003840:Deoxycholic Acid; D012965:Sodium Chloride