Imaging of lactic acid bacteria with AFM - Elasticity and adhesion maps and their relationship to biological and structural data

Prisca Schaer-Zammaretti, Job Ubbink

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The adhesion of lactic acid bacteria to the intestinal epithelium is one of the most important factors determining probiotic ability of a bacterial strain. Studying bacterial adhesion requires knowledge of the structure and properties of the bacterial surface, which can be studied by atomic force microscopy under native conditions. The observation of the surface topography of bacteria from the species Lactobacillus crispatus, L. helveticus and L. johnsonii shows major differences between bacteria having a crystalline-like protein layer as part of the cell wall and those without such layers. Force volume images calculated into elasticity and adhesion force maps of different bacterial strains show that L. crispatus and L. helveticus have a surface with a homogeneous stiffness with no adhesion events. This is most likely caused by the S-layer, which completely covers the surface of the bacteria. We infer that the absence of adhesion peaks is caused by the semi-crystalline character of such protein layers, in agreement with the results obtained from electron microscopy. Analysis of a number of L. johnsonii strains shows that these bacteria have surface properties which strongly differ from the L. crispatus and L. helveticus strains. For L. johnsonii DMS20533 and L. johnsonii ATCC33200 high adhesion forces are observed, which can be related to a surface rich in polysaccharides. L. johnsonii ATCC332 has lower adhesion forces compared to the other two and, furthermore, the surface topography shows depressions. We suppose that this strain has a surface pattern consisting of crystalline-like proteins alternating with polysaccharide-rich domains. The wide variety in surface properties of lactobacilli could well have wide-ranging implications for food processing and for health benefits.

Original languageEnglish (US)
Pages (from-to)199-208
Number of pages10
Issue number1-4
StatePublished - 2003
Externally publishedYes

Bibliographical note

Funding Information:
For the AFM experiments the support of Alcon Laboratories Inc., Fort Worth (Texas) is acknowledged. In particular, we would like to thank J. Cagle for enabling us to work at Alcon and A. Griggs for carrying out a number of AFM experiments. For assistance in the development of the staining technique for TEM, we are grateful to M.-L. Dillmann. For their continuous support, the authors would like to acknowledge M. Fischer and A. Burbidge. For the microbiological support, we are indebted to N. D’Amico and M. Ventura. For the support in the development of the computational routines, we are indebted to U. Ziegler (University of Zürich) and C. Schär (ETH Zürich). The management of Nestec Ltd. is thanked for the permission to publish the work.


  • Adhesion
  • Atomic force microscopy (AFM)
  • Cell wall
  • Elasticity
  • Force vs. distance curves
  • Lactic acid bacteria
  • Molecular interactions
  • Probiotics


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