Biology Reference
In-Depth Information
A continuing challenge with AFM images is distinguishing structures
or molecules of interest on the cell surface. In electron microscopy,
immunolabelled nanoparticles are often used, and this technique has
also been implemented in AFM under dry conditions and in liquid. Plomp
and Malkin used immunolabelled gold nanoparticles to target epitopes on
the surface of
spores.
58
By using both monoclonal and polyclonal
antibodies, they successfully targeted epitopes on both the spore coat and
the underlying exosporium. Using nanoparticles coated with secondary
antibodies to anti-lipoarabinomannan, Alsteens
Bacillus
. showed that the four
drugs they investigated led to exposure of hydrophilic lipoarabinomannan on
the surface of mycobacteria.
59
et al
3.4 APPICATIONS OF AFM TO MICROBIOLOGY
The potential applications of AFM in microbiology are numerous and diverse.
Published reports based on AFM imaging of whole cells have exploited AFM's
spatial resolution capabilities and ability to operate in liquid environments.
Characterizing a microbial cell's response to chemicals is a common application
in which images before and after chemical treatment are compared. Microbial
imaging is contributing to the understanding of morphological characteristics
of single cells, their extracellular structures, bacterial communities such as
bioilms and microbial responses to everything from growth conditions to
antibiotics and nanoparticle exposure. Considering the wide variety of cells
and the diverse array of chemical environments, the use of AFM for such
applications will likely continue to grow. The capability to study dynamic
biological processes at the nanoscale is a unique attribute of AFM that
continues to evolve. Studies using AFM for this purpose have been reported
and were somewhat dependent on improvements in sample preparation
and mounting techniques. Other applications such as the measurement of
interaction forces on living cells and cellular elasticity are being described
in other chapters in this volume. Therefore, imaging-based applications of
AFM are selected for review in the following section. The reader is referred to
other chapters for discussions concerning force spectroscopy applications.
3.4.1 AFM Studies of Microbial Response to Chemical Changes
AFM has been used to study microbial response to different growth
conditions and to exposure to various antimicrobial treatments. Most of
these studies have been performed on dry samples, but a few are dynamic
studies of living cells that have been carried out in liquid environments.
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