Use of Atomic Force Microscopy and Transmission Electron Microscopy for Correlative Studies of Bacterial Capsules

Bacteria can possess an outermost assembly of polysaccharide molecules, a capsule, which is attached to their cell wall. We have used two complementary, high-resolution microscopy techniques, atomic force microscopy (AFM) and transmission electron microscopy (TEM), to study bacterial capsules of fou...

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Bibliographic Details
Published in:Applied and Environmental Microbiology 2008-09, Vol.74 (17), p.5457-5465
Main Authors: Stukalov, Oleg, Korenevsky, Anton, Beveridge, Terry J, Dutcher, John R
Format: Article
Language:English
Subjects:
Bacteria
Bacterial Adhesion
Bacterial Capsules - ultrastructure
Bacteriological Techniques
Biological and medical sciences
Cell walls
Cells
Correlation analysis
Escherichia coli
Freeze Substitution
Fundamental and applied biological sciences. Psychology
Gram-Negative Bacteria - ultrastructure
Methods
Microbiology
Microscopy, Atomic Force
Microscopy, Electron, Transmission
Studies
Transmission electron microscopy
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Summary:Bacteria can possess an outermost assembly of polysaccharide molecules, a capsule, which is attached to their cell wall. We have used two complementary, high-resolution microscopy techniques, atomic force microscopy (AFM) and transmission electron microscopy (TEM), to study bacterial capsules of four different gram-negative bacterial strains: Escherichia coli K30, Pseudomonas aeruginosa FRD1, Shewanella oneidensis MR-4, and Geobacter sulfurreducens PCA. TEM analysis of bacterial cells using different preparative techniques (whole-cell mounts, conventional embeddings, and freeze-substitution) revealed capsules for some but not all of the strains. In contrast, the use of AFM allowed the unambiguous identification of the presence of capsules on all strains used in the present study, including those that were shown by TEM to be not encapsulated. In addition, the use of AFM phase imaging allowed the visualization of the bacterial cell within the capsule, with a depth sensitivity that decreased with increasing tapping frequency.
ISSN:0099-2240
1098-5336
1098-6596
DOI:10.1128/AEM.02075-07