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Monash University biochemists have found a critical piece in the
evolutionary puzzle that explains how life on Earth evolved millions of
The team, from the School of Biomedical Sciences, has described the
process by which bacteria developed into more complex cells and found
this crucial step happened much earlier in the evolutionary timeline
than previously thought.
Team leader and ARC Federation Fellow Trevor Lithgow said the
research explained how mitochondria -- the power house of human and
other cells, which provide complex eukaryotic cells with energy and
ability to produce, divide and move -- were thought to have evolved
about 2000 million years ago from primitive bacteria.
"We have now come to understand the processes that drove cell
evolution. For some time now the crux of this problem has been to
understand how eukaryotes first came to be. The critical step was to
transform small bacteria, passengers that rode within the earliest
ancestors of these cells, into mitochondria, thereby beginning the
evolution of more complex life-forms," Professor Lithgow said.
The team found that the cellular machinery needed to create
mitochondria was constructed from parts pre-existing in the bacterium.
These parts did other jobs for the bacterium, and were cobbled together
by evolution to do something new and more exciting.
"Our research has crystallised with work from other researchers
around the world to show how this transformation happened very early on
-- that the eukaryotes were spawned by integrating the bacterium as a
part of themselves. This process jump-started the evolution of complex
life much more rapidly than was previously thought."
The research consisted of two components, the first used computers to
read, compare and understand DNA sequences. From this, experiments were
designed to do actual laboratory testing using a bacterium that is the
closest living relative to the original ancestor of the mitochondria.
The research was published in the journal Science.
Professor Lithgow said the latest findings were only made possible
due to a gradual gathering of evidence within the scientific community
and recent developments in genome sequencing. "We can now "read" with
great care and insight genome sequences -- the complete DNA sequence of
any organism. From these sequences we find tell-tale clues to the past.
Our findings are relevant to all species, including the evolution of
humans," Professor Lithgow said.
"It continues to amaze that this theory, proposed in the century
before the advent of molecular investigations, is so accurate on a
molecular scale. This improved understanding is directly relevant to the
big picture timeline for the evolution of life."
Professor Lithgow said the findings will be regarded by some
scientists as controversial as many have long-held views on the process
of evolution as a tinkerer. "This will surprise and may even spark
debate. However our research compliments the basic rules of life. Even
at the molecular level, the rules of the game are the same. Evolution
drives biology to more and more complex forms," Professor Lithgow said.
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