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Wednesday, July 21, 1999 Published at 15:21 GMT 16:21 UK


Toughest bug reveals genetic secrets

Pyrococcus abyssi was found living in a deep-sea vent

By BBC News Online Science Editor Dr David Whitehouse

One of the hardiest microbes on Earth, Pyrococcus abyssi, has just had its entire genetic blueprint deciphered.

P. abyssi was found in samples taken during a deep-sea expedition to a hydrothermal vent system. The genes which allow them to survive the extreme conditions could be of great use to bio-industry.

The vents are some of the most inhospitable places on Earth. There is no sunlight, the temperature is over 100 degrees Centigrade and the pressure is hundreds of times more intense than on the Earth's surface.

[ image: Part of P abyssi's ATGC genetic code]
Part of P abyssi's ATGC genetic code
Vents are where super-heated water squirts out of the sea floor. The geyser, full of chemicals and minerals, is called a "black smoker".

Towers and funnels grow around the vent and are home to some of the strangest life forms on Earth - blind shrimps, huge tubeworms and many kinds of micro-organisms.

Pyrococcus abyssi was isolated from inside a vent 3,500 metres (11,500 feet) below the ocean surface in the southwest Pacific.

It likes conditions that the vast majority of other organisms would find impossible to live in. It thrives best at temperatures of about 103 degrees Centigrade and under pressures of about 200 atmospheres.

Magic molecules

An international team of scientists has just completed a map of the 1.7 million segments of its DNA, as part of an international effort to determine the genetic blueprints of organisms which live in unusual places.

Scientists are very interested in such "extremophiles". Not only do they reveal that life can adapt to environments that were thought to be impossible but also because the molecular basis of that adaptation could provide industrial spin-offs.

For example, in order to survive microbes like Pyrococcus abyssi have to have a sophisticated and robust DNA repair mechanism based on heat-stable enzymes.

At such high temperatures the microbe's DNA undergoes continual damage and in order to survive that DNA must be repaired. The molecules that do this must be able to carry out their job without themselves being destroyed by the high temperature and pressure.

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