HEPES-Stabilized Encapsulation of Salmonella typhimurium
- 10 December 2006
- journal article
- research article
- Published by American Chemical Society (ACS) in Langmuir
- Vol. 23 (3), 1365-1374
- https://doi.org/10.1021/la0621721
Abstract
Most bacteria, planktonic and sessile, are encapsulated inside loosely bound extracellular polymeric substance (EPS) in their physiological environment. Imaging a bacterium with its capsule requires lengthy sample preparation to enhance the capsular contrast. In this study, Salmonella typhimurium was investigated using atomic force microscopy for a practical means of imaging an encapsulated bacterium in air. The investigation further aimed to determine the relation between the buffers used for preparing the bacterium and the preservation of the capsular material surrounding it. It was observed that rinsing bacteria with HEPES buffer could stabilize and promote capsule formation, while rinsing with PBS, Tris, or glycine removes most of the capsular EPS. For bacteria rinsed with HEPES and air-dried, the height images showed only the contour of the capsular material, while the phase and amplitude images presented the detailed structures of the bacterial surface, including the flagella encapsulated inside the capsular EPS. The encapsulation was attributed to the cross-linking of the acidic exopolysaccharides mediated by the piperazine moiety of HEPES through electrostatic attraction. This explanation is supported by encapsulated bacteria observed for samples rinsed with N,N'-bis(2-hydroxyethyl)-piperazine solution and by the presence of entrapped HEPES within the dry capsular EPS suggested by micro-Raman spectroscopy.Keywords
This publication has 47 references indexed in Scilit:
- Using nanotechniques to explore microbial surfacesNature Reviews Microbiology, 2004
- Small-Angle X-ray Scattering and Rheological Characterization of Alginate Gels. 3. Alginic Acid GelsBiomacromolecules, 2003
- AFM Imaging Artifacts due to Bacterial Cell Height and AFM Tip GeometryLangmuir, 2003
- Dynamic atomic force microscopy methodsSurface Science Reports, 2002
- Dynamic microprobing of viscoelastic polymer propertiesPolymer International, 2000
- The effect of extracellular polymeric substances on the attachment ofPseudomonasNCIMB 2021 to AISI 304 and 316 stainless steelBiofouling, 2000
- Characteristic features of the major components of freshwater colloidal organic matter revealed by transmission electron and atomic force microscopyColloids and Surfaces A: Physicochemical and Engineering Aspects, 1999
- Attachment of apseudomonassp. to Fe(III)‐(hydr)oxide surfacesGeomicrobiology Journal, 1998
- Comparative studies of bacterial biofilms on steel surfaces using atomic force microscopy and environmental scanning electron microscopyBiofouling, 1996
- Site specificity of metallic ion binding in Escherichia coli K-12 lipopolysaccharideCanadian Journal of Microbiology, 1986