title: The effects of low-shear stress on Adherent-invasive Escherichia coli.
abstract: The impact of low-shear stress (LSS) was evaluated on an Adherent-invasive Escherichia coli clinical isolate (AIEC strain O83:H1) from a Crohn's disease patient. High-aspect ratio vessels (HARVs) were used to model LSS conditions to characterize changes in environmental stress resistance and adhesion/invasive properties. Low-shear stress-grown cultures exhibited enhanced thermal and oxidative stress resistance as well as increased adherence to Caco-2 cells, but no changes in invasion were observed. An AIEC rpoS mutant was constructed to examine the impact of this global stress regulator. The absence of RpoS under LSS conditions resulted in increased sensitivity to oxidative stress while adherence levels were elevated in comparison with the wild-type strain. TnphoA mutagenesis and rpoS complementation were carried out on the rpoS mutant to identify those factors involved in the LSS-induced adherence phenotype. Mutagenesis results revealed that one insertion disrupted the tnaB gene (encoding tryptophan permease) and the rpoS tnaB double mutant exhibited decreased adherence under LSS. Complementation of the tnaB gene, or medium supplemented with exogenous indole, restored adhesion of the rpoS tnaB mutant under LSS conditions. Overall, our study demonstrated how mechanical stresses such as LSS altered AIEC phenotypic characteristics and identified novel functions for some RpoS-regulated proteins.
authors.affiliation: Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555-1070, USA.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Allen
authors.forename: David W
authors.initials: DW
authors.lastname: Niesel
authors.forename: Alfredo G
authors.initials: AG
authors.lastname: Torres
mesh_terms: D026905:Amino Acid Transport Systems / Q000235:genetics; D001422:Bacterial Adhesion / Q000235:genetics / Q000502:physiology*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics; D002460:Cell Line; D003424:Crohn Disease / Q000382:microbiology; D004251:DNA Transposable Elements; D004926:Escherichia coli / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics; D017353:Gene Deletion; D005816:Genetic Complementation Test; D006358:Hot Temperature; D006801:Humans; D016254:Mutagenesis, Insertional; D018384:Oxidative Stress; D012808:Sigma Factor / Q000096:biosynthesis / Q000235:genetics
chemical_list: D026905:Amino Acid Transport Systems; D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D029968:Escherichia coli Proteins; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; C035131:TnaB protein, E coli