Biology Reference
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3.4.2 AFM Studies of Dynamic Biological Processes
One of the most attractive prospects of AFM for biologists is the possibility
to study dynamic biological processes, such as bacterial growth, in an
environment simulating the natural one. Studying dynamic biological
processes is in several aspects more challenging than studying static processes.
If growth is the focus of the study, biological parameters like temperature and
growth media have to be kept constant and favourable, while maintaining
stable immobilization during the study. Because cell surface remodelling may
occur during dynamic processes, immobilization remains a key challenge.
Nevertheless, studying dynamic biological processes at high resolution can be
enabled by AFM studies. Growth and septum formation of
have been
visualized using AFM, and the results were in good correlation with images of
cell division obtained by transmission electron microscopy.
23
The growth of
bacteria immobilized on patterned surfaces has also been observed.
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S. aureus
(a)
(b)
(c)
(d)
(e)
Figure 3.6.
Dynamic AFM imaging was used to study germination of
B. atrophaeus
spores. In this study, spores were immobilized on polycoated vinyl plastic surfaces
for imaging in liquid at 37°C. Spores were irst imaged in water (a) followed by the
addition of germination solution. Onset of germination (b) is irst observed by cracks
(arrows) appearing in the spore surface. These cracks continue to expand (c-e),
resulting in the inal release of vegetative cells. This process can take 2-15 hours.
Scale bars: 500 nm. Image courtesy of M. Plomp and A. J. Malkin. Reproduced with
permission from Ref. 31. Copyright 2007, National Academy of Sciences, U.S.A.
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