Thesis-PDF - IAP/TU Wien
Thesis-PDF - IAP/TU Wien
Thesis-PDF - IAP/TU Wien
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Chapter 4<br />
Euglena gracilis<br />
4.1 Overview<br />
4.1.1 Introduction<br />
The algal flagellate Euglena has for long been an outstanding subject of study for<br />
biologists. It has been maintained in culture in many laboratories as an experimental<br />
organism and almost every biology student has observed it during microscopy<br />
courses. As of today this species is one of the most completely studied. ([82])<br />
These small yet complex organisms dispose over a plethora of bionanotechnological<br />
machinery in order to live, survive and procreate. Their long feature list<br />
includes amongst others a flexible outer shell (the pellicle) that protects them, a<br />
mobile thread (the emergent flagellum) that propels them with high speed through<br />
the liquid, a protein crystal that enables them to sense light and chloroplasts<br />
that convert sunlight photons into storable energy. This energy is in turn stored<br />
through means of lipid vesicles and semicrystalline starch deposits (paramylum 1<br />
grains). If the cell cannot use its flagellum for locomotion it can move by metabolic<br />
movements (this so-called "euglenoid movement" is similar to that of a worm contracting<br />
the back and extending the front part) - sliding along solid material and<br />
being lubricated by its own muciferous lubricant excreted from pellicle pores.<br />
The ability to feed on sunlight only (although it must take up the vitamin<br />
B-12, which it cannot synthesize itself, from the surrounding) and to survive even<br />
with no light present at all by forcing itself to heterotrophic 2 metabolism has raised<br />
some discussion whether this organism is more ’plant-like’ or ’animal-like’. Photosynthesis<br />
(and its prerequisites, the chloroplast plastids within the cell) is a strong<br />
argument to classify it amongst plants, yet an Euglena cell has no cellulose cell wall<br />
1 "paramylum" is equivalent to "paramylon"<br />
2 Heterotrophic means that the cell requires organic substrates as source for carbon in order<br />
to grow and develop.<br />
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