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Impact of an alpha helix and a cysteine-cysteine disulfide bond on the resistance of bacterial adhesion pili to stress
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)ORCID iD: 0000-0002-9835-3263
2021 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 118, no 21, article id e2023595118Article in journal (Refereed) Published
Abstract [en]

Escherichia coli express adhesion pili that mediate attachment to host cell surfaces and are exposed to body fluids in the urinary and gastrointestinal tracts. Pilin subunits are organized into helical polymers, with a tip adhesin for specific host binding. Pili can elastically unwind when exposed to fluid flow forces, reducing the adhesin load, thereby facilitating sustained attachment. Here we investigate biophysical and structural differences of pili commonly expressed on bacteria that inhabit the urinary and intestinal tracts. Optical tweezers measurements reveal that Class 1a pili of uropathogenic E. coli (UPEC), as well as Class 1b of enterotoxigenic E. coli (ETEC), undergo an additional conformational change beyond pilus unwinding, providing significantly more elasticity to their structure than ETEC Class 5 pili. Examining structural and steered molecular dynamics simulation data, we find this difference in Class 1 pili subunit behavior originates from an alpha-helical motif that can unfold when exposed to force. A disulfide bond cross-linking beta-strands in Class 1 pili stabilizes subunits, allowing them to tolerate higher forces than Class 5 pili that lack this covalent bond. We suggest that these extra contributions to pilus resiliency are relevant for the UPEC niche since resident bacteria are exposed to stronger, more transient drag forces compared to those experienced by ETEC bacteria in the mucosa of the intestinal tract. Interestingly, Class 1b ETEC pili include the same structural features seen in UPEC pili, while requiring lower unwinding forces that are more similar to those of Class 5 ETEC pili.

Place, publisher, year, edition, pages
2021. Vol. 118, no 21, article id e2023595118
National Category
Other Physics Topics Biophysics
Identifiers
URN: urn:nbn:se:umu:diva-181870DOI: 10.1073/pnas.2023595118ISI: 000659436300016Scopus ID: 2-s2.0-85106364234OAI: oai:DiVA.org:umu-181870DiVA, id: diva2:1540786
Funder
Swedish Research CouncilThe Kempe FoundationsAvailable from: 2021-03-30 Created: 2021-03-30 Last updated: 2023-09-05Bibliographically approved
In thesis
1. KNOW YOUR ENEMY: Characterizing Pathogenic Biomaterials Using Laser Tweezers
Open this publication in new window or tab >>KNOW YOUR ENEMY: Characterizing Pathogenic Biomaterials Using Laser Tweezers
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Diseases caused by pathogenic agents such as bacteria and viruses result in devastating costs on personal and societal levels. However, it is not just the emergence of new diseases that is problematic. Antibiotic resistance among bacteria makes uncomplicated infections difficult and lethal. Resilient disease-causing spores spread in hospitals, the food industry, and water supplies requiring effective detection and disinfection methods. Further, we face complex neurological diseases where no effective treatment or diagnostic methods exist. Thus, we must increase our fundamental understanding of these diseases to develop effective diagnostic, detection, disinfection, and treatment methods.

Classically, the methods used for detecting and studying the underlying mechanics of pathogenic agents work on a large scale, measuring the average macroscopic behavior and properties of these pathogens. However, just as with humans, the average behavior is not always representative of individual behavior. Therefore, it is also essential to investigate the characteristics of these pathogens on a single cell or particle level. 

This thesis develops and applies optical techniques to characterize pathogenic biomaterial on a single cell or particle level. At the heart of all these studies is our Optical Tweezers (OT) instrument. OT are a tool that allows us to reach into the microscopic world and interact with it. Finally, by combining OT with other experimental techniques, we can chemically characterize biomaterials and develop assays that mimic different biological settings. Using these tools, we investigate bacterial adhesion, disinfection, and detection of pathogenic spores and proteins.

Hopefully, the insights of these studies can lessen the burden on society caused by diseases by helping others develop effective treatment, diagnostic, detection, and disinfection methods in the future. 

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2022. p. 73
Keywords
Optical Tweezers, Laser Tweezers, Raman Spectroscopy, Bacterial Adhesion, Biophysics, Pili, Bacterial Spores, Endospores, Oocysts, Cryptosporidium, Optics
National Category
Biophysics Atom and Molecular Physics and Optics
Research subject
biology; Physics
Identifiers
urn:nbn:se:umu:diva-192471 (URN)978-91-7855-726-4 (ISBN)978-91-7855-727-1 (ISBN)
Public defence
2022-03-11, NAT.D.410, Naturvetarhuset, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2022-02-18 Created: 2022-02-14 Last updated: 2022-02-15Bibliographically approved

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Dahlberg, TobiasAndersson, Magnus

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