Biology Reference
In-Depth Information
nanomechanical properties with intact
.
33
The study showed that non-
contact imaging of live spheroplasts provided the best images. Furthermore,
despite using a soft cantilever, the pliability of the untreated spheroplast
surface prevented measurement of its elastic properties.
Diatoms are single-cell photosynthetic algae that are found in all bodies of
water. There are tens of thousands of species of diatoms that are differentiated
by the silica skeletons which are derived from the minute concentrations of
silicic acid found in the water. From an ecological standpoint, diatoms are
critical components of the ecosystem. From a materials standpoint, they
serve as an ideal model system for understanding natural strategies to the
synthesis and patterning of hard materials. As revealed by AFM, formation
of the silica skeleton can begin with fusion of silica beads as small as 40 nm
to create highly ordered micron-scale structures.
84
Determining how these
skeletons are produced with accuracy spanning the nano to the macroscale
exceeds our synthetic capabilities. The accuracy of the diatom's biosynthetic
capability, to reproduce its silica skeleton, is illustrated in the example of the
AFM images of the large diatom
E. coli
shown i
n
Figure 3.7
.
The
AFM analysis of diatoms, not only in terms of structure but also adhesive
and mechanical properties, is an active area of research that can be further
accessed in reviews
Gyrosigma balticum
85-87
as well as in
Chapter 19
.
3.5 FUTURE DIRECTIONS
Earlier efforts in applying AFM to microbiology had a necessary focus on
demonstrating the applicability of AFM to such studies and on addressing
technical concerns related to the mounting and imaging of microbial cells.
In the process, AFM has proven valuable for understanding the physical and
morphological responses of the cell to hydration and chemical treatment.
Elucidating the physical consequences of antibiotic treatment will likely be a
topic of continued interest.
The spatial resolution afforded by AFM allows examination of structural
changes related to such exposures as well as detailed investigation of
extracellular structures and biological processes such as cell division and
sporulation. Although high-resolution imaging of living microbial cells will
continue to be a deining attribute of AFM imaging, the ield is transitioning
from the study of static biological samples to dynamic measurements of
living systems. Reining capabilities to characterize dynamic processes will
be essential. Such advances will likely beneit from reinements in procedures
for mounting and imaging but also from improvements in instrumentation.
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