scholarly journals Contribution of Type IV Pili to the Virulence of Aeromonas salmonicida subsp. salmonicida in Atlantic Salmon (Salmo salar L.)

2008 ◽  
Vol 76 (4) ◽  
pp. 1445-1455 ◽  
Author(s):  
Jessica M. Boyd ◽  
Andrew Dacanay ◽  
Leah C. Knickle ◽  
Ahmed Touhami ◽  
Laura L. Brown ◽  
...  
Keyword(s):  
Atlantic Salmon ◽  
Bacterial Pathogen ◽  
Aeromonas Salmonicida ◽  
Type Iv Pili ◽  
Wild Type ◽  
Gene Encoding ◽  
Force Microscopy ◽  
Type Iv ◽  
Atomic Force ◽  
Pilin Subunit

ABSTRACT Aeromonas salmonicida subsp. salmonicida, a bacterial pathogen of Atlantic salmon, has no visible pili, yet its genome contains genes for three type IV pilus systems. One system, Tap, is similar to the Pseudomonas aeruginosa Pil system, and a second, Flp, resembles the Actinobacillus actinomycetemcomitans Flp pilus, while the third has homology to the mannose-sensitive hemagglutinin pilus of Vibrio cholerae. The latter system is likely nonfunctional since eight genes, including the gene encoding the main pilin subunit, are deleted compared with the orthologous V. cholerae locus. The first two systems were characterized to investigate their expression and role in pathogenesis. The pili of A. salmonicida subsp. salmonicida were imaged using atomic force microscopy and Tap- and Flp-overexpressing strains. The Tap pili appeared to be polar, while the Flp pili appeared to be peritrichous. Strains deficient in tap and/or flp were used in live bacterial challenges of Atlantic salmon, which showed that the Tap pilus made a moderate contribution to virulence, while the Flp pilus made little or no contribution. Delivery of the tap mutant by immersion resulted in reduced cumulative morbidity compared with the cumulative morbidity observed with the wild-type strain; however, delivery by intraperitoneal injection resulted in cumulative morbidity similar to that of the wild type. Unlike the pili of other piliated bacterial pathogens, A. salmonicida subsp. salmonicida type IV pili are not absolutely required for virulence in Atlantic salmon. Significant differences in the behavior of the two mutant strains indicated that the two pilus systems are not redundant.

scholarly journals Nanoscale Characterization and Determination of Adhesion Forces of Pseudomonas aeruginosa Pili by Using Atomic Force Microscopy

2006 ◽  
Vol 188 (2) ◽  
pp. 370-377 ◽  
Author(s):  
Ahmed Touhami ◽  
Manfred H. Jericho ◽  
Jessica M. Boyd ◽  
Terry J. Beveridge
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Atomic Force Microscopy ◽  
Type Iv Pili ◽  
Adhesion Forces ◽  
Chain Polymer ◽  
Force Microscopy ◽  
Type Iv ◽  
Atomic Force ◽  
Force Curves ◽  
The Individual

ABSTRACT Type IV pili play an important role in bacterial adhesion, motility, and biofilm formation. Here we present high-resolution atomic force microscopy (AFM) images of type IV pili from Pseudomonas aeruginosa bacteria. An individual pilus ranges in length from 0.5 to 7 μm and has a diameter from 4 to 6 nm, although often, pili bundles in which the individual filaments differed in both length and diameter were seen. By attaching bacteria to AFM tips, it was possible to fasten the bacteria to mica surfaces by pili tethers. Force spectra of tethered pili gave rupture forces of 95 pN. The slopes of force curves close to the rupture force were nearly linear but showed little variation with pilus length. Furthermore, force curves could not be fitted with wormlike-chain polymer stretch models when using realistic persistence lengths for pili. The observation that the slopes near rupture did not depend on the pili length suggests that they do not represent elastic properties of the pili. It is possible that this region of the force curves is determined by an elastic element that is part of the bacterial wall, although further experiments are needed to confirm this.

scholarly journals Biofilm formation by Pseudomonas aeruginosa wild type, flagella and type IV pili mutants

2003 ◽  
Vol 48 (6) ◽  
pp. 1511-1524 ◽  
Author(s):  
Mikkel Klausen ◽  
Arne Heydorn ◽  
Paula Ragas ◽  
Lotte Lambertsen ◽  
Anders Aaes-Jørgensen ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Biofilm Formation ◽  
Type Iv Pili ◽  
Wild Type ◽  
Type Iv

scholarly journals Trans-dimerization of JAM-A regulates Rap2 and is mediated by a domain that is distinct from the cis-dimerization interface

2014 ◽  
Vol 25 (10) ◽  
pp. 1574-1585 ◽  
Author(s):  
Ana C. Monteiro ◽  
Anny-Claude Luissint ◽  
Ronen Sumagin ◽  
Caroline Lai ◽  
Franziska Vielmuth ◽  
...  
Keyword(s):  
Epithelial Cell Proliferation ◽  
Wild Type ◽  
Transfected Cells ◽  
Force Microscopy ◽  
Atomic Force ◽  
Unique Site ◽  
Dimerization Interface ◽  
In Trans ◽  
In Cis ◽  
Common Cell

Junctional adhesion molecule-A (JAM-A) is a tight junction–associated signaling protein that regulates epithelial cell proliferation, migration, and barrier function. JAM-A dimerization on a common cell surface (in cis) has been shown to regulate cell migration, and evidence suggests that JAM-A may form homodimers between cells (in trans). Indeed, transfection experiments revealed accumulation of JAM-A at sites between transfected cells, which was lost in cells expressing cis- or predicted trans-dimerization null mutants. Of importance, microspheres coated with JAM-A containing alanine substitutions to residues 43NNP45 (NNP-JAM-A) within the predicted trans-dimerization site did not aggregate. In contrast, beads coated with cis-null JAM-A demonstrated enhanced clustering similar to that observed with wild-type (WT) JAM-A. In addition, atomic force microscopy revealed decreased association forces in NNP-JAM-A compared with WT and cis-null JAM-A. Assessment of effects of JAM-A dimerization on cell signaling revealed that expression of trans- but not cis-null JAM-A mutants decreased Rap2 activity. Furthermore, confluent cells, which enable trans-dimerization, had enhanced Rap2 activity. Taken together, these results suggest that trans-dimerization of JAM-A occurs at a unique site and with different affinity compared with dimerization in cis. Trans-dimerization of JAM-A may thus act as a barrier-inducing molecular switch that is activated when cells become confluent.

scholarly journals Loss of PRCD alters number and packaging density of rhodopsin in rod photoreceptor disc membranes

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Emily R. Sechrest ◽  
Joseph Murphy ◽  
Subhadip Senapati ◽  
Andrew F. X. Goldberg ◽  
Paul S.-H. Park ◽  
...  
Keyword(s):  
High Fidelity ◽  
Rod Photoreceptor ◽  
Photoreceptor Degeneration ◽  
Wild Type ◽  
Photoreceptor Outer Segment ◽  
Rod Photoreceptors ◽  
Force Microscopy ◽  
Atomic Force ◽  
Photoreceptor Neurons ◽  
Precise Role

Abstract Progressive rod-cone degeneration (PRCD) is a small protein localized to photoreceptor outer segment (OS) disc membranes. Several mutations in PRCD are linked to retinitis pigmentosa (RP) in canines and humans, and while recent studies have established that PRCD is required for high fidelity disc morphogenesis, its precise role in this process remains a mystery. To better understand the part which PRCD plays in disease progression as well as its contribution to photoreceptor OS disc morphogenesis, we generated a Prcd-KO animal model using CRISPR/Cas9. Loss of PRCD from the retina results in reduced visual function accompanied by slow rod photoreceptor degeneration. We observed a significant decrease in rhodopsin levels in Prcd-KO retina prior to photoreceptor degeneration. Furthermore, ultrastructural analysis demonstrates that rod photoreceptors lacking PRCD display disoriented and dysmorphic OS disc membranes. Strikingly, atomic force microscopy reveals that many disc membranes in Prcd-KO rod photoreceptor neurons are irregular, containing fewer rhodopsin molecules and decreased rhodopsin packing density compared to wild-type discs. This study strongly suggests an important role for PRCD in regulation of rhodopsin incorporation and packaging density into disc membranes, a process which, when dysregulated, likely gives rise to the visual defects observed in patients with PRCD-associated RP.

Structure and assembly-disassembly properties of wild-type transthyretin amyloid protofibrils observed with atomic force microscopy

2011 ◽  
Vol 24 (3) ◽  
pp. 467-476 ◽  
Author(s):  
Ricardo H. Pires ◽  
Maria J. Saraiva ◽  
Ana M. Damas ◽  
Miklós S. Z. Kellermayer
Keyword(s):  
Atomic Force Microscopy ◽  
Wild Type ◽  
Force Microscopy ◽  
Atomic Force

scholarly journals Quantitative atomic force microscopy measurements of Acinetobacter morphology

2020 ◽  
Author(s):  
C. Phoebe Lostroh ◽  
Caroline M. Boyd ◽  
Nicholas Lammers ◽  
Kaleb S. Roush ◽  
Sara L. Worsham ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Growth Curve ◽  
Cell Shape ◽  
Nanometer Scale ◽  
Growth Media ◽  
Wild Type ◽  
Acinetobacter Baylyi ◽  
Force Microscopy ◽  
Atomic Force ◽  
Morphology Changes

Abstract Acinetobacter baylyi are variously reported as spherical or rod-shaped. Here we use atomic force microscopy (AFM) to make quantitative nanometer-scale measurements of cellular length and width for thousands of individual cells. We quantify the heterogeneity of populations grown in varying environmental conditions that dramatically affect cell shape. In particular, we look at morphology changes across a growth curve, and we examine cells from populations grown in various growth media. We also examine the morphology of a minC mutant, which suggests an interpretation for the morphological types observed in wild type cells.

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