Page 124 - 79_04

Microalgae:
the
first
nuclear
engineers?

that
allow
rapid
adaptation
of
mesophyle
microalgae
to
extreme
environment
of

the
uranium
pond
(Figure
2).

Figure
2.-­-
Schematic
diagram
of
the
possible
results
of
a
modified
fluctuation
analysis
by

Lopez-­-Rodas
et
al.,
(2001),
from
a
classic
Luria
and
Delbrück
(1943)
method.Two
sets
of

experiments
were
performed:
in
set
1,
96
cultures,
founded
from
an
initial
inoculums
of
N0
=102

cells,
were
propagated
until
Nt=105
cells
without
selective
conditions
and
then,
Saelices
water

enriched
with
BG11
medium
was
added.
The
result
obtained
from
set1
was
i)
adaptation
thanks
for

rare
pre-­-selective
mutations
occurred
randomly
before
the
exposure
to
Saelices
water
during
the

propagations
of
the
cultures.
The
differences
between
the
culture
flasks
depend
in
the
early
or
late

occurrence
of
the
mutational
event
(arrows
show
the
culture
flasks
that
presented
growth).
The

other
two
possible
results
of
set1
are:
ii)
physiological
acclimation
or
post-­-adaptive
mutations
(the

cell
number
among
the
culture
flasks
must
be
similar)
and
iii)
no
adaption
at
all
(empty
culture

flasks).
In
set
2,
used
as
a
control
in
other
to
sample
the
variance
of
the
paternal
population,
the
30

replicates
had
initially
N0=
105
cell
from
the
same
parental
culture.
The
result
obtained
in
set
2
was

a
similar
number
of
resistance
cells
in
all
the
cultures.

A
massive
destruction
of
cells
was
observed
in
each
experimental
culture
of

both
sets
1
and
2
in
the
fluctuation
analysis
with
Saelices
evaporation
pond
water.

However,
after
further
incubation
during
10
weeks
proliferation
of
living
resistant

cells
was
observed
in
7
cultures
of
set
1
experiments
of
C.
reinhardtii.

Simultaneously
proliferation
of
resistant
cells
was
also
detected
in
all
the
cultures

of
set
2.
The
fluctuation
in
the
number
of
resistant
cells
observed
in
set
1

experiment
significantly
exceeded
the
fluctuation
observed
in
set
2
controls
(set
1

639