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Response
of biological systems in vivo under space conditions and solar VUV
irradiation.
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(a)
Optical image of one Aspergillus terreus spore immobilized on the
silica wafer. The average size of spores is ~3 microns.
(b) 2D-AFM image of one Aspergillus terreus spore with 100-200 nm
granular star structure around the periphery of its elliptic shape.
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This
work is a part of ESA/EU SURE project aiming to quantify the survival
probability of fungal spores in space under solar irradiation in
the vacuum ultraviolet (VUV) (110-180 nm) spectral region. The contribution
and impact of VUV photons, vacuum, low temperature and their synergies,
on the survival probability of Aspergillus terreus spores is measured
at simulated space conditions on Earth. To simulate the solar VUV
irradiation, the spores are irradiated with a continuous discharge
VUV hydrogen photon source and a molecular fluorine laser, at low
and high photon intensities at 1015 photon m-2
s-1 and 3.9 x 1027 photons pulse-1
m-2 s-1 respectively. The survival probability
of spores is independent from the intensity and the fluence of photons,
within certain limits, in agreement with previous studies. The spores
are shielded from a thin carbon layer, which is formed quickly on
the external surface of the proteinaceous membrane at higher photon
intensities at the start of the VUV irradiation. Extrapolated the
results in space conditions, for an interplanetary direct transfer
orbit from Mars to Earth, the spores will be irradiated with 3.3
x 1021 solar VUV photons m-2 . This photon
fluence is equivalent to the irradiation of spores on Earth with
54 laser pulses with an experimental ~92% survival probability,
disregarding the contribution of space vacuum and low temperature,
or to continuous solar VUV irradiation for 38 days in space near
the Earth with an extrapolated ~61% survival probability. The experimental
results indicate that the damage of spores is mainly from the dehydration
stress in vacuum. The high survival probability after 4 days in
vacuum (~34 %), is due to the exudation of proteins on the external
membrane, preventing thus further dehydration of spores. In addition,
the survival probability is increasing to (~54%) at 10 K with 0.12
K/s cooling and heating rate.
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(a)
3D-AFM image of a part of the surface of Aspergillus terreus spore
with rough vesicle structures.
(b) 2D-AFM image of conidiophore elongated structure.
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(a)
AFM high resolution image (phase mode) of one A. terreus spore with
20 nm wide rodlet structure on granular domains.
(b) AFM image of damaged A. terreus spores after 24h at 10-4
Pa. The damaged spores appear with extende drod-like structure on
the surface (Point A), indicating excessive biologicalactivity.
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(a)
Optical image of an area of the wafer with spores prior to exposure
in vacuum.
(b)Theoptical image of the same area after 24h at 10-4
Pa and 298K.
The density of spores is lesser than of the non-exposed sample due
to dehydration.
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(a)
AFM image of a damaged dehydrated A. terreus spore exposed at 10K
and 10-4 Pa for 24h.
(b)AFM of an intact spore (A)and a damaged one(B)at the same experimental
conditions.
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(a)
AFM image of A. terreus spores following 24h at VUV irradiation
at 10-4 Pa and 10K.Some cracks and holes appear on the external
membrane of spores(A). The cellular content of exploded spores,100200nm
wide is spread around (B).
(b) AFM image of A. terreus spore exposed at 10K in vacuum 10-4
Pa for 24h. One spore with dimension 2 microns X 1.6 microns together
with the spores remnants is indicated.
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(a)
AFM image of damaged dehydrated spores after 24h at 10-4 Pa and
298K. The shape of cells is deformed and some parts of spores are
squeezed. The cellular content of exploded spores is spread around.
(b) AFM image of a damaged A. terreus spores after 60 min of laser
irradiation in vacuum with a hole at the centre. Part of the cellular
content is shown next to the spore.
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(a)
AFM image of damaged spores after 60min of laser irradiation at
10-4 Pa. The cellular content is scattered around.
(b) Survival probability of spores following laser irradiation at
157nm, 15Hz at 10-4 Pa and in nitrogen at 105 Pa at 10, 30 and 60
min,respectively.
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Relevant
Publications
- Interplanetary
survival probability of Aspergillus terreus spores under simulated
solar vacuum ultraviolet irradiation.
E. Sarantopoulou, I. Gomoiu, Z. Kollia and A.C. Cefalas,
Planet. Space Sci. 59, 63 (2011).
DOI:
10.1016/j.pss.2010.11.002
- Preventing
biological activity of Ulocladium sp spores in artifacts using
157nm laser.
E. Sarantopoulou, Z. Kollia and I. Gomoiu,
Appl. Phys. A 83, 663 (2006).
DOI:
10.1007/s00339-006-3554-8
- Removing Foxing stains from old
paper at 157 nm.
E. Sarantopoulou, Z. Samardzija, S. Kobe, Z. Kollia and A. C.
Cefalas.
Appl. Surf. Sci. 208-209, 311 (2003).
DOI:
10.1016/S0169-4332(02)01379-X
- Efficient removing of foxing
from a medieval Ptolemaic map using a molecular laser at 157nm.
A. C. Cefalas, E. Sarantopoulou and Z. Kollia.
Appl. Phys. A, 73, 571 (2001).
- Lasers and Biodeterioration.
I. Gomoiu, R. Radvan, E. Sarantopoulou and A. C. Cefalas,
M. Schreiner, M. Strlic (eds.)
Handbook on the Use of Lasers in Conservation and Conservation
Science, COST G7 (2006).
Conference
Presentations
- Preparing ulocladium cultures
for studies in microgravity conditions.
I. Gomoiu, E. Sarantopoulou and Z. Kollia,
ELGRA-AIMAS Symposium,Plant Biology 2 session, Florence,
Italy, 4-7 september (2007).
- VUV
laser cleaning of fungus and Lichens from Hellenic archeological
stones.
E. Sarantopoulou , Z. Kollia, A. C. Cefalas and I. Gomoiu,
EMRS 2007, Strasburg France, May 28 - June 1, (2007).
- Atomic
resolution etching of external proteinacious protective membrane
of
ulocladium and aspergillus 1-4 spores in vivo.
E. Sarantopoulou,
Z. Kollia, I. Gomoiu,
3rd Workshop on Nanoscience & Nanotechnologies N&N 06,
Thessaloniki Greece,10-12 July (2006).
- Preventing
biological activity of Ulocladium sp spores in artifacts using
157-nm laser.
E. Sarantopoulou, Z.
Kollia and I. Gomoiu,
EMRS 2005, 31st May-3rd June, Strasbourg France (2005).
- Laser
treatment of foxing at 157nm.
E. Sarantopoulou, Z. Samardzija, S. Kobe, M. Besenicar, Z. Kollia,
P. Argitis and A.C. Cefalas ,
EMRS 2002, Strasbourg France, 18-21 June (2002).
- Restoration
of Historic paper using Vacuum Ultraviolet Lasers.
E. Sarantopoulou, Z. Kollia and A. C. Cefalas,
Lasers 2001, Tucson Arizona USA, 4-8 December (2001).
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48,
Vassileos Constantinou Aven. 11635 Athens, Greece
Tel: +30 210 7273840, Fax: +30 210 7273842, email :ccefalas@eie.gr
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