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Helix-like bio-polymers can act as effective dampers for bacteria in flows
Umeå University, Faculty of Science and Technology, Department of Physics. (The Biophysics and Biophotonics group)
Umeå University, Faculty of Science and Technology, Department of Physics. (The Biophysics and Biophotonics group)
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Physics. (The Biophysics and Biophotonics group)
2012 (English)In: European Biophysics Journal, ISSN 0175-7571, E-ISSN 1432-1017, Vol. 41, no 6, 551-560 p.Article in journal (Refereed) Published
Abstract [en]

Biopolymers are vital structures for many liv- ing organisms; for a variety of bacteria, adhesion polymers play a crucial role for the initiation of colonization. Some bacteria express, on their surface, attachment organelles (pili) that comprise subunits formed into stiff helix-like structures that possess unique biomechanical properties. These helix-like structures possess a high degree of flexi- bility that gives the biopolymers a unique extendibility. This has been considered beneficial for piliated bacteria adhering to host surfaces in the presence of a fluid flow. We show in this work that helix-like pili have the ability to act as efficient dampers of force that can, for a limited time, lower the load on the force-mediating adhesin-receptor bond on the tip of an individual pilus. The model presented is applied to bacteria adhering with a single pilus of either of the two most common types expressed by uropathogenic Escherichia coli, P or type 1 pili, subjected to realistic flows. The results indicate that for moderate flows (~25 mm/s) the force experienced by the adhesin-receptor interaction at the tip of the pilus can be reduced by a factor of ~6 and ~4, respectively. The uncoiling ability pro- vides a bacterium with a ‘‘go with the flow’’ possibility that acts as a damping. It is surmised that this can be an important factor for the initial part of the adhesion process, in particular in turbulent flows, and thereby be of use for bacteria in their striving to survive a natural defense such as fluid rinsing actions.

Place, publisher, year, edition, pages
Springer, 2012. Vol. 41, no 6, 551-560 p.
Keyword [en]
fimbriae, pili, uncoiling, damping, bacterial adhesion
National Category
Other Physics Topics Biophysics
Research subject
Physics; biology
Identifiers
URN: urn:nbn:se:umu:diva-54018DOI: 10.1007/s00249-012-0814-8OAI: oai:DiVA.org:umu-54018DiVA: diva2:515002
Available from: 2012-04-11 Created: 2012-04-11 Last updated: 2017-12-07Bibliographically approved
In thesis
1. The mechanics of adhesion polymers and their role in bacterial attachment
Open this publication in new window or tab >>The mechanics of adhesion polymers and their role in bacterial attachment
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Bacterial resistance to antibiotics is increasing at a high rate in both developing and developed countries. To circumvent the problem of drug-resistant bacterial pathogens, we need to develop new effective methods, substances, and materials that can disarm and prevent them from causing infections. However, to do this we first need to find new possible targets in bacteria to approach and novel strategies to apply.Escherichia coli (E. coli) bacteria is a normal member of the intestinal microflora of humans and mammals, but frequently cause diverse intestinal and external diseases by means of virulence factors, which leads to hundreds of million sick people each year with a high mortality rate. An E. coli bacterial infection starts with adhesion to a host cell using cell surface expressed adhesion polymers, called adhesion pili. Depending on the local environment different types of pili are expressed by the bacteria. For example, bacteria found in the gastrointestinal tract commonly express different pili in comparison to those found in the urinary tract and respiratory tract. These pili, which are vital for bacterial adhesion, thereby serve as a new possible approach in the fight against bacterial infections by targeting and disabling these structures using novel chemicals. However, in order to develop such chemicals, better understanding of these pili is needed.Optical tweezers (OT) can measure and apply forces up to a few hundred pN with sub-pN force resolution and have shown to be an excellent tool for investigating mechanical properties of adhesion pili. It has been found that pili expressed by E. coli have a unique and complex force-extension response that is assumed to be important for the ability of bacteria to initiate and maintain attachment to the host cells. However, their mechanical functions and the advantage of specific mechanical functions, especially in the initial attachment process, have not yet been fully understood.In this work, a detailed description of the pili mechanics and their role during cell adhesion is presented. By using results from optical tweezers force spectroscopy experiments in combination with physical modeling and numerical simulations, we investigated how pili can act as “shock absorbers” through uncoiling and thereby lower the fluid force acting on a bacterium. Our result demonstrate that the dynamic uncoiling capability of the helical part of the adhesion pili modulate the force to fit the optimal lifetime of its adhesin (the protein that binds to the receptor on the host cell), ensuring a high survival probability of the bond.iiiSince the attachment process is in proximity of a surface we also investigated the influence of tether properties and the importance of different surface corrections and additional force components to the Stokes drag force during simulations. The investigation showed that the surface corrections to the Stokes drag force and the Basset force cannot be neglected when simulating survival probability of a bond, since that can overestimate the probability by more than an order of magnitude.Finally, a theoretical and experimental framework for two separate methods was developed. The first method can detect the presence of pili on single cells using optical tweezers. We verified the method using silica microspheres coated with a polymer brush and E. coli bacteria expressing; no pili, P pili, and type 1 pili, respectively. The second method was based on digital holography microscopy. Using the diffraction of semi-transparent object such as red blood cells, we showed that this method can reconstruct the axial position and detect morphological changes of cells.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2015. 65 p.
Keyword
Pili, optical tweezers, bacterial adhesion, fimbriae, uncoiling
National Category
Other Physics Topics Biophysics
Identifiers
urn:nbn:se:umu:diva-109524 (URN)978-91-7601-331-1 (ISBN)
Public defence
2015-10-23, Naturvetarhuset, N420, Umeå universitet, Umeå, 13:00 (English)
Opponent
Supervisors
Available from: 2015-10-02 Created: 2015-09-30 Last updated: 2015-10-02Bibliographically approved

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Zakrisson, JohanWiklund, KristerAxner, OveAndersson, Magnus

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