Thesis-PDF - IAP/TU Wien

into fully functional chloroplasts again as soon as enough light becomes available.
But even with its chloroplasts Euglena is not fully photoautotroph - it cannot
synthesize vitamin B12. The alga can therefore be used to prove the occurrence
of vitamin B12.
4.3.6 Vacuole
Under the Reservoir, Euglena possesses a contractile vacuole, that can excrete
water that diffused into the cell interior in the sweet water regime. The concentration
of osmotically active elements within the cell is higher than in the sweet water
surrounding (a hypertonic regime). The cell wall is a semipermeable membrane,
letting pass water molecules but not bigger ones. The concentration gradient
between inside and outside is heading towards an equilibrium and must be counteracted
by the vacuole that acts as a pump. 15 The vacuole surrounds the bases
of the flagella. It is limited by a unit membrane and, when full has a diameter of
5µm. It pulsates rhythmically, every 20-30 seconds it discharges.
This is an example of natural nanotechnology that controls precisely in which
environment the processes should run. Encapsulation plays an important role, as
certain functions have to be constrained to a subdomain, where environmental
conditions are guaranteed to be stable within certain limits.
4.4 Technical Applications
Each of the subsystems exhibits a range of properties desirable in technical applications.
Photoreceptor
As one of the most interesting nanotechnological elements in Euglena, the high
yield of photons means a good sensing performance, thermal stability and tunable
wavelengths. Conversion of electrical into chemical energy.
A natural fit as application could be a data storage system. A disk coated by a
layer of photoreceptor protein could be written on by activation and deactivation of
individual chromophore proteins (repeatable). Laser light of the right wavelength
could be used for the switching and the low thermal deactivation as well as the
simple photocycle make it suited for this task.
15 The hypertonic solution has the lower osmotic pressure of two fluids. It also describes a cell
environment with a lower concentration of solutes than the cytosol of the cell. In a hypertonic
environment, osmosis causes a net flow of water into the cell, that can lead the cell to swell and
even burst.
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