Do Immobilization Methods Affect Force Spectroscopy Measurements of Single Bacteria?

Laura J. Waldman, Martha E. Grady

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


Increasing antibiotic resistance in bacteria is a critical issue that often leads to infections or other morbidities. Mechanical properties of the bacterial cell wall, such as thickness or elastic modulus, may contribute to the ability of a bacterial cell to resist antibiotics. Techniques like atomic force microscopy (AFM) are used to quantify bacterial cell mechanical properties and image cell structures at nanoscale resolutions. An additional benefit of AFM is the ability to probe samples submerged in liquids, meaning that live bacteria can be imaged or evaluated in environments that more accurately simulate in vivo conditions as compared to other methods like electron microscopy. However, because AFM measurements are highly sensitive to small perturbations in the deflection of the tip of a sensor probe brought into contact with the specimen, immobilization of bacteria prior to measurement is essential for accurate measurements. Traditional chemical fixatives crosslink the molecules within the bacterial cell wall, which prevent the bacteria from locomotion. While effective for imaging, chemical crosslinkers are known to affect the measured stiffness of eukaryotic cells and also may affect the measured stiffness of the bacterial cell wall. Alternative immobilization methods include Cell-Tak™, an adhesive derived from marine mussels that does not interact with the bacterial wall and filters with known pore sizes which entrap bacteria. Previous studies have examined the effect of these immobilization methods on successful imaging of bacteria but have not addressed differences in measured modulus. This study compares the effects of immobilization methods including chemical fixatives, mechanical entrapment in filters, and Cell-Tak™ on the stiffness of the bacterial cell wall as measured by force spectroscopy.

Original languageEnglish
Title of host publicationChallenges in Mechanics of Time-Dependent Materials and Mechanics of Biological Systems and Materials, Volume 2 - Proceedings of the 2022 Annual Conference on Experimental and Applied Mechanics
EditorsAlireza Amirkhizi, Jevan Furmanski, Christian Franck, Karen Kasza, Aaron Forster, Jon Estrada
Number of pages4
StatePublished - 2023
EventSEM Annual Conference and Exposition on Experimental and Applied Mechanics, 2022 - Pittsburgh, United States
Duration: Jun 13 2022Jun 16 2022

Publication series

NameConference Proceedings of the Society for Experimental Mechanics Series
ISSN (Print)2191-5644
ISSN (Electronic)2191-5652


ConferenceSEM Annual Conference and Exposition on Experimental and Applied Mechanics, 2022
Country/TerritoryUnited States

Bibliographical note

Publisher Copyright:
© 2023, The Society for Experimental Mechanics, Inc.


  • Atomic force microscopy
  • Live cell immobilization
  • Mechanobiology

ASJC Scopus subject areas

  • General Engineering
  • Computational Mechanics
  • Mechanical Engineering


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