French Advances in Science and Technology May 28, 2002 – Issue #339
** WHEN LAST WE LEFT OUR HEROS ON THE SHORES OF LAKE VOSTOK
The Vostok saga continues, as findings from the latest investigation of ice
core samples, in experiments carried on jointly by Russian and French
scientists in Grenoble, suggest in good saga fashion that external life
turns out to be an illusion but true life is to be found on the inside.
The
story begins when a Russian ice coring project bores down through the 4
km-thick glacial cover on top of a huge paleo-lake, stopping just short to
avoid being blown to Valhalla by the release of 350 atmospheres of pressure,
and also to avoid contaminating what might be a precious record of ancient
life. (FAST #132) Although early Vostok cores mainly yielded global warming
insights based on their record of climate history, a French scientist
triggered an avalanche of US/French/Russian research activity by
demonstrating that the lowest cores were in fact refrozen lake water and
therefore should contain traces of any bacterial life as might exist in the
possibly 1 million-year-old lake.
In the ensuing showdown, Americans drew
first and fired, but for many critics their claims of having found bacterial
life were wide of the mark. Franco-Russian doubts persisted, convinced that
the bacteria found had ridden in with kerosene and other products used in
drilling and were not aboriginal. (FAST #301) This week at the American
Geophysical Union meetings in Washington, French researchers from Grenoble’s
Glaciology Laboratory along with biologists from the University of Grenoble
are presenting findings from a painstaking examination of the cores carried
out in collaboration with Russian scientists in an ultra-clean sterile
laboratory in Grenoble, a research program born of their doubts.
In order to
distinguish what’s on the outside from what’s on the inside, the team cut
the 10 cm core into three concentric layers, and examined them separately.
Confirming their suspicions of contamination, they found that life was a
great deal more abundant on the outside of the sample than at the core’s
core. The big news is that nevertheless there is life in the lake, as
molecular biology techniques detected a few fragments of DNA in the inner
layer, belonging to three different bacterial strains. One resembles a
bacteria known to live in hydrothermal springs at moderate temperatures, but
the other two are close to a bacteria found in hot springs, strange
travelers to find in water maintained in liquid form at -3¡C by pressure.
Early theories suggest that lake water infiltrated deep into bedrock and
picked up the creatures at a geo-spa. In Grenoble thoughts are turning
already to designing a sanitized robot to explore the lake. (LibŽration, May
28, p22, Sylvestre Huet)
** ADAM AND EUCARYOTE
If Lake Vostok bacteria go back along way (see above), they don’t
necessarily go all the way back. Those who don’t care for the Eden version
of first earthlings need to come up with some alternative candidate among
all us living creatures.
Focusing up till now on what kind of living entity
it would take to survive the quite ungarden-like conditions of early Earth,
theorists have posited hyperthermophiliac bacteria grouped around undersea
geysers, sources of food and energy, as the front-running forebear. Taking a
completely different approach, a phylogeneticist from the Laboratory for
Phylogenetics, Bio-Informatics, and Genome Studies of Pierre and Marie Curie
University in Paris has devised an analytic technique for comparing the
genome of numerous bacteria to establish a sort of chronological hierarchy
among them. If the statistical techniques employed are reliable then it
would appear that the prize for first across the starting line should go to
a group of bacteria known as planctomycetales, whose need for extremes goes
no further than a bit of cold water. And if this is true, it will require
some significant rewriting of theories of evolutionary history.
For
planctomycetales possess the unique feature of a membrane around their
chromosomes, but this membrane does not on the other hand constitute a cell
nucleus. This leaves planctomycetales in no man’s land between procaryotes,
which are creatures lacking nuclei, such as other bacteria, and eucaryotes,
that is the rest of us who are made of one or more nucleus-equipped cells.
Standard assumptions about the history of species has procaryotes appearing
on stage before eucaryotes, which are cast as an evolutionary step up. The
distinction may prove to be less fundamental than supposed, but before
conclusions of such a nature are drawn, further phylogenetic research and
tool-testing needs to be carried out. (LibŽration, May 27, p22, Franois
Lassagne)
