Imaging Bacteria

SEM image of Burkholderia cepacia G4.
Obtained with the assistance of Mr. David Bentley at the University of Arizona.

Imaging Bacteria, Biopolymers, and Colloidal Particles

The following page provides example images of colloids. For more information on the specific research projects related to these images, please contact me.

We have used atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) to image bacteria. Each technique has advantages and disadvantages.In electron microscopy, the samples must be placed under ultrahigh vacuum. This could cause some artifacts in the images. In general, SEM provides a nice view of the cell's overall shape and size, but we were unable to resolve any surface features of the bacteria.

Bacterial were also imaged with AFM. The AFM images shown here were captured under ambient conditions. Under these conditions, a thin layer of water (1-2 nm) rests on top of the sample surface, so the sample may still be considered hydrated. It is also possible to capture AFM images completely in liquid, but we have found the contrast of these images to be generally poor. From AFM images, we were best able to resolve features on the bacterial surfaces.

AFM image of Pseudomonas putida KT2442. The left image is topographic, the right image is a phase image.

Biopolymers, such as the polysaccharide schizophyllan, can also be imaged with AFM.

AFM image of polysaccharide schizophyllan on mica.
Polymer prepared with the assistance of Dr. Françoise Muenier at the University of Geneva.

One thing we were not able to do very well with AFM was to locate bacterial flagella. TEM was the best technique for trying to image the flagella of a bacterium.

TEM image of Pseudomonas fluorescens P17.
Obtained with the assistance of Mr. David Bentley at the University of Arizona.

We also have used Environmental Scanning Electron Microscopy (ESEM).In this technique, the vacuum does not have to be as high. Although it was difficult to use this technique for imaging individual bacteria, ESEM was very useful in trying to image biofilms and colloidal particles on soil grains.

Left: ESEM image of biofilm of Pseudomonas fluorescens P17.
Obtained with the assistance of Mr. David Bentley at the University of Arizona.

Right: ESEM image of 1 µm latex microspheres deposited on an Arizona soil.
Obtained with the assistance of Dr. Maria Klimkiewicz at the Pennsylvania State University.

To learn more, see the homepages of my collaborators on this work:

More images of similar samples can be found in these references:

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Last modified: November 05, 2007 09:48:18