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November 21, 2005 — Bacteria feel pressures to
evolve antibiotic resistance and other new abilities in response to a
changing environment, and they react by 'stealing' genetic information
from other better-adapted types of bacteria, according to research
published in Nature Genetics.
They do this through the bacterial equivalent of sex, otherwise
known as horizontal gene transfer, through which bacteria obtain
genetic material from their distant relatives. This allows them to
evolve the networks of chemical reactions that enable them to do new
things, such as defend themselves against antibiotics or antibacterial
In the first ever systematic study of how bacteria change their
‘metabolic networks’, researchers have been able to piece together the
history of new metabolic genes acquired by the E.coli bacterium over
the last several 100 million years.
They estimate that approximately 25 of E.coli’s roughly 900
metabolic genes have been added into its network through horizontal
gene transfer in the last 100 million years. This compares to just one
addition by the most common source of new genes in animals, gene
duplication, where copies of genes are made by accident and then
altered over time.
To test why these new genes were needed by E.coli, the researchers
cross examined dozens of E.coli’s closest bacterial relatives to see
which genes were most commonly exchanged between them. This would
highlight the genes that have contributed the most to the evolution of
metabolic networks across bacteria.
They found that most of these genes helped bacteria cope with
specific environments. Thus, new genes were needed for new functions,
not to make the bacteria better at what they were doing anyway.
“Metabolic networks are systems of interacting proteins, which
perform the chemistry with which a bacterium builds its own
components,” said Dr Martin Lercher from the University of Bath.
“Bacteria often acquire new genes by direct transfer from other
types of bacteria; in a way, that's the bacterial world's sex, and it
plays a crucial role in how pathogenic bacteria acquire resistance to
“For the first time, we have analysed how this mechanism allows complete metabolic networks to change over evolutionary time.
“We found that bacteria use new genes not to improve their
performance in the environments they already know, but to adapt to new
or changing environments; and accordingly, genetic changes happen at
their interface with the environment.
“Bacteria feel pressures to change in response to a changing world,
and they react by 'stealing' genetic information from other, better
adapted, types of bacteria. In this way, bacteria are just as lazy as
humans: why invent the wheel twice if someone else has already found a
solution to your problem?”
The research also involved scientists from the European Molecular
Biology Laboratory(Germany), Eötvös Lorànd University (Hungary) and the
University of Manchester (UK).
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