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Endospore pili - flexible, stiff and sticky nanofibers
Department of Paraclinical Sciences, Faculty of Veterinary Medicine, Norwegian University of Life Sciences (NMBU), Ås, Norway.
Umeå University, Faculty of Science and Technology, Department of Physics.ORCID iD: 0000-0002-0496-6692
Umeå University, Faculty of Science and Technology, Department of Physics.ORCID iD: 0000-0002-0168-0197
Umeå University, Faculty of Science and Technology, Department of Physics.
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2023 (English)In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 122, no 13, p. 2696-2706Article in journal (Refereed) Published
Abstract [en]

Species belonging to the Bacillus cereus group form endospores (spores) whose surface is decorated with micrometers-long and nanometers-wide endospore appendages (Enas). The Enas have recently been shown to represent a completely novel class of Gram-positive pili. They exhibit remarkable structural properties making them extremely resilient to proteolytic digestion and solubilization. However, little is known about their functional and biophysical properties. In this work, we apply optical tweezers to manipulate and assess how wild type and Ena-depleted mutant spores immobilize on a glass surface. Further, we utilize optical tweezers to extend S-Ena fibers to measure their flexibility and tensile stiffness. Finally, by oscillating single spores, we examine how the exosporium and Enas affect spores’ hydrodynamic properties. Our results show that S-Enas (μm long pili) are not as effective as L-Enas in immobilizing spores to glass surfaces but are involved in forming spore to spore connections, holding the spores together in a gel-like state. The measurements also show that S-Enas are flexible but tensile stiff fibers, which support structural data suggesting that the quaternary structure is composed of subunits arranged in a complex to produce a bendable fiber (helical turns can tilt against each other) with limited axial fiber extensibility. Lastly, the results show that the hydrodynamic drag is 1.5-times higher for wild type spores expressing S- and L-Enas compared to mutant spores expressing only L-Enas or ”bald spores” lacking Ena, and 2-times higher compared to spores of the exosporium deficient strain. This study unveils novel findings on the biophysics of S- and L-Enas, their role in spore aggregation, binding of spores to glass, and their mechanical behavior upon exposure to drag forces.

Place, publisher, year, edition, pages
Elsevier, 2023. Vol. 122, no 13, p. 2696-2706
Keywords [en]
aggregation, pili, adhesion, optical tweezers, spore
National Category
Biophysics Other Physics Topics Microbiology
Identifiers
URN: urn:nbn:se:umu:diva-208834DOI: 10.1016/j.bpj.2023.05.024ISI: 001059849200001PubMedID: 37218131Scopus ID: 2-s2.0-85160684458OAI: oai:DiVA.org:umu-208834DiVA, id: diva2:1761402
Part of project
Biophysical and Physicochemical Fingerprinting of Single Bacterial Spores, Swedish Research Council
Funder
Swedish Research Council, 2019-04016Available from: 2023-06-01 Created: 2023-06-01 Last updated: 2025-09-30Bibliographically approved
In thesis
1. Spotlight the killer: detecting harmful chemical and biological agents using optical spectroscopy
Open this publication in new window or tab >>Spotlight the killer: detecting harmful chemical and biological agents using optical spectroscopy
2025 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Lyset på mördaren : detektion av skadliga kemiska och biologiska ämnen med hjälp av optisk spektroskopi
Abstract [en]

Harmful chemical and biological agents are a significant threat to health and prosperity worldwide. Recent years have seen an increase in wars and conflicts around the globe, raising concerns about the potential deployment of chemical and biological warfare agents. On a less speculative level, harmful chemicals such as narcotic substances cause immense humanitarian and economic damage through overdoses and associated healthcare costs, while microbes such as pathogenic bacteria and parasites cause hospital-acquired infections and food spoilage at a cost of approximately 1 trillion euros every year. To combat the threat of these harmful agents, we must thus develop rapid and effective detection and diagnostic methods for harmful agents, allowing us to effectively deploy specific treatments and preventative measures.

Classically, while there exist numerous methods for the detection of both harmful chemical and biological agents, they often come with limitations that inhibit their effectiveness. These inhibitions often take the form of bulky equipment that is difficult to apply in the field or time-consuming preparation and measurement processes.

In this thesis we will explore an alternative category of assays for detecting and characterizing harmful materials – optical spectroscopy. Optical spectroscopy is a category of material characterization methods that use light to probe a material. While probing the material, we receive a signal characteristic of the molecules, chemical, and biological structure of our material. These optical spectroscopic methods, such as Raman spectroscopy and fluorescence spectroscopy, can be used to characterize a material within the span of minutes or even seconds, making them ideal for detection applications. Furthermore, they can often be made portable or even handheld, making them a great tool for initial field indication of harmful materials, ahead of thorough lab analysis.

I sincerely hope the studies presented herein can serve as a stepping stone to future technologies and detection assays, capable of saving both money and lives. 

Place, publisher, year, edition, pages
Umeå: Umeå University, 2025. p. 72
Keywords
Sensing, Raman spectroscopy, SERS, Fluorescence spectroscopy, CWA, nerve agents, bacterial spores, Cryptosporidium
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:umu:diva-244830 (URN)978-91-8070-780-0 (ISBN)978-91-8070-779-4 (ISBN)
Public defence
2025-10-24, Aula Anatomica, Biologihuset, 907 36, Umeå, Umeå, 13:00 (English)
Opponent
Supervisors
Note

This work was done in collaboration with, and with support from, the Swedish Defece Research Agency (FOI).

Available from: 2025-10-03 Created: 2025-09-30 Last updated: 2025-10-22Bibliographically approved

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Malyshev, DmitryÖberg, RasmusDahlberg, TobiasAndersson, Magnus

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