Science Report

April 11, 2008

Jan Gruber



Science Report: Biochemistry

Today we finalized the dataset for the samples that were collected for
the RSL project. All in all, we have collected soil samples at 12
different locations. These sites were selected because they showed
either signs of recent water / evaporation (e.g.: washes, evaporation
basins) or because they had “salty” looking deposits on the surface.

Samples were collected using the corer in accordance with the
protocols provided by Shannon (15cm core, clean but not sterile corer,
store in sterile 50 ml Falcon tubes) – even though it was not always
possible to get to the full 15 cm into the ground.

At each location, we took GPS coordinates, photos as well as two core
samples (tubes A and B). The A samples were used for determination of
salinity and humidity and for some of our own lab experiments, while B
sample tubes were kept sealed for future analysis by the RSL project.

Salinity and humidity were determined for each sample using the
following protocols:

Salinity: Approximately 1g of each soil samples (from sample tube A)
was suspended into 40 ml of distilled water. The suspension was kept at
RT for approximately 1h with frequent agitation. The suspension was
allowed to settle and salinity was then determined using the portable
salinity meter. For calibration purposes we also prepared NaCl
standards ( 1 mg / 40 ml, 5 mg / 40 ml, 10 mg / 40 ml, 50 mg / 40 ml
and 100 mg / 40 ml. This was done to express salinity both in absolute
numbers ( uS as given by the uncalibrated salinity meter) as well as
relative to NaCl standards (NaCl equivalent per g of soil). The last
part could, however, not be completed because the batteries of the
salinity meter died before the NaCl curve could be established. No
replacements could be found.

Humidity: For each sample approximately 5g of sample were transferred
from sample tube A onto a piece of aluminum foil. The weight of the
foil as well as of the soil sample was established accurately using the
digital lab scale. The samples were then dried for several hours (at
last 3 – better over night) at 50 C. Once samples were obviously dry
(light, powdery appearance), the weight of the dried samples was
established. Relative humidity was expressed in weight loss due to
drying per g of original soil sample.

The 12 samples have been labeled clearly as C 70–1B to C70-12 B.
Photos, GPS coordinates, salinity and humidity have been compiled into
a Word document, which will be packed with the sample tubes as well, and
left for Shannon. In accordance with protocol,
samples will be stored at RT - outside of direct sunlight but not in
the dark. We have also compiled these protocols for future reference
and these will be sent to Shannon.
Additionally we have taken video showing sample collection procedures
(both for sterile collection of extremophiles from rock surfaces and
for non-sterile core sampling) and we will try to edit these and make
them available – but this will have to wait until we are back on earth.


One interesting event for today was that we got nice bacterial looking
growth on one of our high salt (3X% w/v) agar plates (see todays
photos). This plate originates from a test extraction of one of our
core samples (extracted into sterile salt water, filtered, centrifuged
– 100 ul plated, incubated for 96h at 37 C). We counted six colonies on
the plate. The control plates show now growth at all, suggesting that
our sterile technique together with the salt selection worked
effectively to avoiding contamination. Consistent with the low colony
count we got zero colonies on a 1/10 dilution plate prepared from the
same extraction. Everybody was very excited and we hope that the RSL
lab will detect many interesting organisms in the 12 samples we
collected.

As this will be the last Biochemistry report from crew 70, I would like
to thank Guerric and Celine who worked tirelessly with me on trying the
various iteration of the protocols - and to everybody for collecting
exciting samples for us. I hope these will be useful for more in depth
investigations on earth – Biochemistry Lab signing off.