DNA code sheds light on world-ranging alga

It's just a tiny thing -- a single-celled organism visible only under a microscope -- yet it is one of the most successful life forms on the planet.

So say scientists who on Wednesday published the DNA code of an ocean alga called Emiliania huxleyi, whose astonishing adaptability enables it to thrive in waters from the equator to the sub-Arctic.

Known under the more useful moniker of "Ehux," the alga has a thin, hard, chalky shell of calcium carbonate.

Condensed piles of billions of long-dead Ehuxes comprise, for instance, the White Cliffs of Dover.

In the ocean, "blooms" of Ehux algae can cover thousands of square kilometres (square miles), and their milky reflected light can be seen from space.

Less visibly, the micro-alga also has an essential place in the ecosystem and the complex equation of climate change, which explains the bid to sequence its genome.

As a phytoplankton, Ehux is a basic link in the ocean's food chain. It also absorbs lots of carbon dioxide (CO2) at the ocean surface, helping to attenuate the greenhouse-gas problem.

Unveiled in Nature, the genome project turned out to be something of a nightmare, the researchers admit.

The Ehux genome was originally thought be only about 30 million bases, or "rungs" in the DNA ladder.

In the end, it turned out to be a whopping 141 million bases, with at least 30,000 genes -- a third more than the gene tally among humans, although our overall genome is many times bigger.

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DNA code sheds light on world-ranging alga