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Genome of Undersea Microbe Surfaces
By Kate Ruder

Over a year ago, scientists uncovered a microbe that lives in hot-water geysers on the ocean floor near Iceland. It appeared to have one of the smallest genomes of any microbe ever found.

The microbe N. equitans, tiny blue dots, grows attached to another microbe, larger blue circles.

The fiery creature is an extremophile, an organism that thrives in extreme environments, such as toxic waste dumps and hot springs . This microbe loves life at around 212°F (100°C), the boiling point of water.

Now scientists—led by Diversa Corporation, a biotechnology company in San Diego, California—have sequenced its genome.

Diversa plans to use the microbe's genetic information to engineer industrial chemicals that work in extreme environments, such as enzymes that break down harmful substances in oil wells.

The newly discovered microbe doesn't live alone. It grows attached to another small microbe, called Ignicoccus. German researchers found the two organisms growing together in hot rocks and gravel at the Kolbeinsey Ridge, north of Iceland.

Ignicoccus cell with four smaller N. equitans cells attached.

At first, the German scientists thought they had found only one organism, Ignicoccus. But when they looked in the microscope, they saw small, round cells growing on it. The cells turned out to be an entirely new species that they named Nanoarchaeum equitans, which they say means ‘riding the fire sphere.'

By looking at its genome, the researchers discovered that the microbe lives as a parasite on Ignicoccus. It's entirely dependent on its host to survive, and they confirmed that it has the smallest genome of any microbe ever sequenced.

The microbe's small genome and small number of genes could make it easier to genetically engineer. Diversa hopes to engineer microbes that are mini-protein factories for drugs, thought this could be a long way off.

Diversa teamed up with Celera Genomics in Rockville , Maryland , who did the actual sequencing, and with Yale University in New Haven, Connecticut.

Diversa and Celera have collaborated on other sequencing projects. They sequenced Streptomyces diversa in February 2001 and then sequenced another heat-loving organism, Pyrolobus fumarii, later that year.

Diversa also plans to sequence the genome of Ignicoccus. Both organisms were discovered by Karl O. Stetter of the University of Regensburg, Germany, who is a scientific founder of Diversa.

The microbes have since been found living in hot springs in Yellowstone National Park.

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Waters, E. et al. The genome of Nanoarcheum equitans: Insights into early archael evolution and derived parasitism. Proceedings of the National Academy of Sciences USA. Published online October 17, 2003.


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