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| Heidelberg, 2 March 2006 |
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| A new tree of life allows a closer look at the
origin of species
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| Tree of life |
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Press
Release 2 March 2006 [PDF]
German
A global evolutionary map reveals new insights into our last common ancestor
In 1870 the German
scientist Ernst Haeckel mapped the evolutionary
relationships of plants and animals in the first 'tree of life'.
Since then scientists have continuously redrawn and
expanded the tree adding microorganisms and using
modern molecular data, yet, many parts of the tree have
remained unclear. Now a group at the European
Molecular Biology Laboratory [EMBL] in Heidelberg has
developed a computational method that resolves many of
the open questions and produced what is likely the most
accurate tree ever. The study, which appears in the
current issue of the journal Science, gives some intriguing
insights into the origins of bacteria and the last common
universal ancestor of all life on earth today.
"DNA sequences of complete genomes provide us with a
direct record of evolution", says Peer Bork, Associate
Coordinator for Structural and Computational Biology at
EMBL, whose group carried out the project. "For a long
time the overwhelming amount of data [the human
genome alone contains enough information to fill 200
telephone books] has made it very difficult to pinpoint the
information needed for a high-resolution map of evolution.
But our study shows how this challenge can be tackled by
combining different computational methods in an
automated process."
Bork's lab specialises in the computational analysis of
genomes, and recently they applied this expertise to the
tree of life. Since all organisms descend from the same
ancestor, they share some common genes. Francesca
Ciccarelli and Tobias Doerks of Bork's group managed to
identify 31 genes with clear relatives in 191 organisms,
ranging from bacteria to humans, to reconstruct their
relationships.
"Even using such genes, you might get the wrong
answer," says Ciccarelli. "Organisms inherit most genes
from their parents, but over the course of evolution, a few
have been obtained when organisms swapped genes with
their neighbours in a process called horizontal gene
transfer [HGT]. Obviously, the latter class of genes does
not tell you anything about your ancestors. The trick was
to identify and exclude them from the analysis."
"This procedure drastically reduced the 'noise' in the data,
making it possible to identify as yet unknown details of
early evolution," says Tobias Doerks. "For example, we
now know that the first bacterium was probably a type
called gram-positive and likely lived at high temperatures
– suggesting that all life arose in hot environments."
The improved tree has also shed light on other research
carried out by the group. Bork and colleagues are
participating in projects that collect genetic material of
unknown species en masse from environments such as
farm soil and ocean floor. "With the new high-resolution
tree in hand, it is now possible to classify genetic material
from this unexplored microbial world and further our
understanding of life on the planet."
Source Article
F. D. Ciccarelli, T. Doerks, C. von Mering, C. J. Creevey, B. Snel & P. Bork. Towards automatic reconstruction of a highly
resolved tree of life. Science, 3 March 2006.
Press Contact
Anna-Lynn Wegener
Press Officer
EMBL Heidelberg
Tel: +49 6221 387 8452
E-mail: wegener@embl.de
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