Thesis-PDF - IAP/TU Wien

Chapter 6
Results
High resolution topographic images of E. gracilis acquired with the Atomic Force
Microscope are presented in this chapter. Algal features found are related to
Euglenoid morphology as presented in chapter 4.
Three major goals were reached during the work on E. gracilis. First, a preparation
method suitable for AFM investigation of E. gracilis had to be developed.
This was found in a special drying process (see section 5.3) that left whole intact
algae to be investigated. Second, AFM data of unprecedented resolution of E.
gracilis were acquired, on the algal pellicle and even on certain cell parts. A third
goal was reached in providing additional AFM data to what is already available
from SEM and TEM investigations. Investigated features of the alga included e.g.
imaging of the mucilage in between pellicle strips, a feature usually not visible
through SEM or TEM due to sample preparation techniques that remove soft biological
material. Our AFM investigation of E. gracilis also revealed new features
that have not been described before.
6.1 Sample Preparation - Challenges and Solutions
The preparation method as presented in 5.3 solved a number of difficulties encountered
with earlier attempts to image the alga.
Firstly, the algal cells burst during the drying process if no precautions are
taken. Fig. 6.1 shows such a burst E. gracilis cell. Obviously, this hinders imaging
of intact cell surfaces and in addition enzymatic activity might damage biological
membranes, alter their properties or slowly dissolve them altogether (autolysis).
Although certain cell features still can be made out this information is unreliable.
A further challenge in the invented drying process had been the amount of
residue of the evaporated nutrient solution. As can be seen in Fig. 6.2, the
embedding residue does not only prevent cells from bursting but can also prevent
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