Change search
ReferencesLink to record
Permanent link

Direct link
Physical Properties of Biopolymers Assessed by Optical Tweezers: Analysis of folding and refolding of bacterial pili
Umeå University, Faculty of Science and Technology, Physics.
Umeå University, Faculty of Science and Technology, Physics.
Umeå University, Faculty of Science and Technology, Chemistry.
Umeå University, Faculty of Medicine, Molecular Biology (Faculty of Medicine). (Uhlin)
Show others and affiliations
2008 (English)In: ChemPhysChem, ISSN 1439-4235, Vol. 9, no 2, 221-235 p.Article in journal (Refereed) Published
Abstract [en]

Bacterial adhesion to surfaces mediated by specific adhesion organelles that promote infections, as exemplified by the pili of uropathogenic E. coli, is studied mostly at the level of cell-cell interactions and thereby reflects the averaged behavior of multiple pili. The role of pilus rod structure has therefore only been estimated from the outcome of experiments involving large numbers of organelles at the same time. It has, however, lately become clear that the biomechanical behavior of the pilus shafts play an important, albeit hitherto rather unrecognized, role in the adhesion process. For example, it has been observed that shafts from two different strains, even though they are similar in structure, result in large differences in the ability of the bacteria to adhere to their host tissue. However, in order to identify all properties of pilus structures that are of importance in the adhesion process, the biomechanical properties of pili must be assessed at the single-molecule level. Due to the low range of forces of these structures, until recently it was not possible to obtain such information. However, with the development of force-measuring optical tweezers (FMOT) with force resolution in the low piconewton range, it has lately become possible to assess forces mediated by individual pili on single living bacteria in real time. FMOT allows for a more or less detailed mapping of the biomechanical properties of individual pilus shafts, in particular those that are associated with their elongation and contraction under stress. This Mi- nireview presents the FMOT technique, the biological model system, and results from assessment of the biomechanical properties of bacterial pili. The information retrieved is also compared with that obtained by atomic force microscopy.

Place, publisher, year, edition, pages
2008. Vol. 9, no 2, 221-235 p.
Keyword [en]
bacterial adhesion, force spectroscopy, mechanical properties, optical tweezers´, single-molecule studies
URN: urn:nbn:se:umu:diva-17336DOI: doi:10.1002/cphc.200700389OAI: diva2:157009
Available from: 2008-01-25 Created: 2008-01-25 Last updated: 2010-03-03Bibliographically approved
In thesis
1. Construction of force measuring optical tweezers instrumentation and investigations of biophysical properties of bacterial adhesion organelles
Open this publication in new window or tab >>Construction of force measuring optical tweezers instrumentation and investigations of biophysical properties of bacterial adhesion organelles
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Optical tweezers are a technique in which microscopic-sized particles, including living cells and bacteria, can be non-intrusively trapped with high accuracy solely using focused light. The technique has therefore become a powerful tool in the field of biophysics. Optical tweezers thereby provide outstanding manipulation possibilities of cells as well as semi-transparent materials, both non-invasively and non-destructively, in biological systems. In addition, optical tweezers can measure minute forces (< 10-12 N), probe molecular interactions and their energy landscapes, and apply both static and dynamic forces in biological systems in a controlled manner. The assessment of intermolecular forces with force measuring optical tweezers, and thereby the biomechanical structure of biological objects, has therefore considerably facilitated our understanding of interactions and structures of biological systems.

Adhesive bacterial organelles, so called pili, mediate adhesion to host cells and are therefore crucial for the initial bacterial-cell contact. Thus, they serve as an important virulence factor. The investigation of pili, both their biogenesis and their expected in vivo properties, brings information that can be of importance for the design of new drugs to prevent bacterial infections, which is crucial in the era of increased bacterial resistance towards antibiotics.

In this thesis, an experimental setup of a force measuring optical tweezers system and the results of a number of biomechanical investigations of adhesive bacterial organelles are presented. Force measuring optical tweezers have been used to characterize three different types of adhesive organelles under various conditions, P, type 1, and S pili, which all are expressed by uropathogenic Escherichia coli. A quantitative biophysical force-extension model, built upon the structure and force response, has been developed. It is found, that this model describes the biomechanical properties for all three pili in an excellent way. Various parameters in their energy landscape, e.g., bond lengths and transition barrier heights, are assessed and the difference in behavior is compared. The work has resulted in a method that in a swift way allows us to probe different types of pili with high force and high spatial resolution, which has provided an enhanced understanding of the biomechanical function of these pili.

Abstract [sv]

Optisk pincett är en teknik i vilken mikrometerstora objekt, inkluderande levande celler och bakterier, beröringsfritt kan fångas och förflyttas med hög noggrannhet enbart med hjälp av ljus. Den optiska pincetten har därmed blivit ett kraftfullt verktyg inom biofysiken, som möjliggör enastående precisions-manipulering av celler och semi-transparenta objekt. Dessutom kan denna manipulation göras intracellulärt, dvs. utan att fysiskt öppna eller penetrera cellernas membran. Den optiska pincetten kan även mäta mycket små krafter och interaktioner (< 10-12 N) samt applicera både statiska och dynamiska krafter i biologiska system med utmärkt precision. Optisk pincett är därför en utmärkt teknik för mätning av intermolekylära krafter och för bestämning av biomekaniska strukturer och dess funktioner.

Vissa typer av bakterier har specifika vidhäftningsorganeller som kallas för pili. Dessa förmedlar vidhäftningen till värdceller och är därför viktiga vid bakteriens första kontakt. En djupare förståelse av pilis uppbyggnad och biomekanik kan därmed ge information, som kan vara vital i framtagandet av nya mediciner som förhindrar bakteriella infektioner. Detta är av stor vikt i skenet av den ökande antibiotikaresistensen i vårt samhälle.

I denna avhandling presenteras konstruktionen av en experimentell uppställning av kraftmätande optiskt pincett tillsammans med resultat från biomekaniska undersökningar av vidhäftande bakteriella organeller. Kraftmätande optisk pincett har använts för att karakterisera tre olika typer av pili, P, typ 1, och S pili, vilka kan uttryckas av uropatogena Escherichia coli. En kvantitativ biofysikalisk modell som beskriver deras förlängningsegenskaper under pålagd kraft har konstruerats. Modellen bygger på pilis strukturella uppbyggnad samt på dess respons som uppmäts med den kraftmätande optiska pincetten. Modellen beskriver de biomekaniska egenskaperna väl för alla tre pili. Dessutom kan ett antal specifika bindnings- och subenhetsparametrar bestämmas, t.ex. interaktionsenergier och bindningslängder. Skillnaden mellan dessa parametrar hos de tre pilis samt deras olika kraftrespons har jämförts. Detta arbete har dels resulterat i en förbättrad förståelse av pilis biomekaniska funktion och dels i en metod som, med hög noggrannhet, tillåter oss att bestämma ett antal biomekaniska egenskaper hos olika organeller på ett effektivt sätt.

Place, publisher, year, edition, pages
Umeå: Fysik, 2007. 79 p.
optical tweezers, biological physics, unfolding, Escherichia coli, force measurements, energy landscape, dynamic force spectroscopy, manipulation, polymers, pili
National Category
Physical Sciences
urn:nbn:se:umu:diva-1425 (URN)978-91-7264-435-9 (ISBN)
Public defence
2007-11-30, N450, Naturvetarhuset, Umeå Universitet Campus, Umeå, 13:00 (English)
Available from: 2007-11-08 Created: 2007-11-08 Last updated: 2009-08-19Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Andersson, MagnusAxner, OveAlmqvist, FredrikUhlin, Bernt EricFällman, Erik
By organisation
PhysicsChemistryMolecular Biology (Faculty of Medicine)
In the same journal

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 196 hits
ReferencesLink to record
Permanent link

Direct link