Optimization of fixation methods for observation of bacterial cell morphology and surface ultrastructures by atomic force microscopy

Appl Microbiol Biotechnol. 2011 Oct;92(2):381-92. doi: 10.1007/s00253-011-3551-5. Epub 2011 Sep 1.

Abstract

Fixation ability of five common fixation solutions, including 2.5% glutaraldehyde, 10% formalin, 4% paraformaldehyde, methanol/acetone (1:1), and ethanol/acetic acid (3:1) were evaluated by using atomic force microscopy in the present study. Three model bacteria, i.e., Escherichia coli, Pseudomonas putida, and Bacillus subtilis were applied to observe the above fixation methods for the morphology preservation of bacterial cells and surface ultrastructures. All the fixation methods could effectively preserve cell morphology. However, for preserving bacterial surface ultrastructures, the methods applying aldehyde fixations performed much better than those using alcohols, since the alcohols could detach the surface filaments (i.e., flagella and pili) significantly. Based on the quantitative and qualitative assessments, the 2.5% glutaraldehyde was proposed as a promising fixation solution both for observing morphology of both bacterial cell and surface ultrastructures, while the methonal/acetone mixture was the worst fixation solution which may obtain unreliable results.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacillus subtilis / chemistry*
  • Bacillus subtilis / ultrastructure
  • Cytological Techniques / instrumentation
  • Cytological Techniques / methods*
  • Escherichia coli / chemistry*
  • Escherichia coli / ultrastructure
  • Microscopy, Atomic Force
  • Pseudomonas putida / chemistry*
  • Pseudomonas putida / ultrastructure