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Amoeba genome sheds new light on human evolution

03/10/2010 10:38:01

A billion years ago life was more complicated than you might think, according to an international team of researchers including a Lancaster University scientist.

Researchers have sequenced the genome of a common soil amoeba called Naegleria gruberi - unlocking a new piece of evidence in the long and complex history of human evolution.

This amoeba is exactly the type of organism that scientists believe lived on the planet more than a billion years ago – yet the analysis published this week in the journal Cell suggests that such ancient organisms had surprisingly complicated lifestyles.

Naegleria has a triple identity: it is a shape-shifting amoeba is highly versatile, containing all the genetic information necessary to survive in a wide range of environments and respond in unexpected ways to a wide range of stresses.

As an amoeba, Naegleria pushes out little feet, called pseudopods that propel it in its hunt for food. Yet, once the food disappears, the amoeba creates flagella (two little tails) and uses them to swim about in search of new hunting grounds. It has a third identity, a hard cyst, that can persist in the soil until conditions become damp and warm enough for it to turn back into an amoeba.

Most single-celled organisms -- in particular, parasites -- have simpler lifestyles and fewer genes.

Consistent with its complicated lifestyle, scientists found Naegleria was packed with genes – almost 16,000 protein-coding genes, which is a relatively high number when compared to the 23,000 or so genes found in humans.

These 16,000 genes predict Naegleria is surprisingly flexible in the way that it can sense and respond to a changing environment, but moreover in making the comparison with an evolutionarily diverse range of organisms, the Naegleria genome annotation team go a long way towards defining the core molecular parts that were already present when the primitive single-celled beasts alive around a billion years ago diverged and evolved to become the animals and plants that we recognise today.

The sequence, produced by the Department of Energy Joint Genome Institute (JGI), and an analysis by scientists from the University of California, Berkeley, University of California, Davis, Lancaster University in the United Kingdom and institutions elsewhere in the United States, Canada, and the U.K. are published in the March 5 issue of the journal Cell.