Mystery bug found in Antarctica's Lake Vostok

There is something alive in Lake Vostok, deep beneath the East Antarctic ice sheet, and we don't know what it is. Water samples from the lake contain a bacterium that does not seem to belong to any known bacterial groups ? although whether it truly is a new form of life remains to be proven.

Russian scientists breached Lake Vostok in February 2012, after years of drilling. The lake lies beneath 3.5 kilometres of ice, and has been cut off from the rest of the world since Antarctica froze 14 million years ago.

The Russians' borehole was filled with lubricating kerosene, which contains bacteria ? causing concerns that the lake might be contaminated. But the project seems to have avoided this. When the drill hit the lake, it automatically withdrew in response to the pressure change. Lake water gushed into the borehole, pushing the kerosene up the hole before freezing.

Since last May, Sergey Bulat of the Petersburg Nuclear Physics Institute in Russia and colleagues have been studying the water that froze onto the drill bit. "The samples proved to be very dirty," he says, with lots of kerosene. Preliminary genetic analyses reported last October found bacteria from the drilling fluid, not the lake.

Bulat has now gone back to the DNA samples. Comparing their DNA sequences to a database of known contaminants, he identified short fragments of DNA belonging to 19 different known bacterial species. "All of them proved to be contaminants, or bacteria from human skin," says Bulat.

More unusual

A twentieth species is more unusual. The genetic samples show less than 86 per cent similarity to the known major groups of bacteria. That could mean it belongs to an entirely new division, says Bulat, although he concedes that it could just be a new species.

"This is encouraging, but we don't really know much about it," says David Pearce of the British Antarctic Survey in Cambridge, UK. He says it would have been surprising if there hadn't been life in Lake Vostok, as organisms manage to survive in all manner of extreme environments. More interesting, he says, is what the life in Vostok looks like, and how different it is to everything else on Earth.

Pearce has studied samples from Lake Hodgson, which lies beneath just a few metres of ice in west Antarctica. He says 25 per cent of the genetic sequences he has found do not match anything found in DNA databases. So on its own, having an unusual DNA sequence does not prove that the Vostok bacterium belongs to a new group. There's a long list of systematic tests that will need to be carried out in order to prove that.

The results must also be independently replicated, says Martin Siegert of the University of Bristol, UK, who led an unsuccessful attempt to drill into another Antarctic lake - Ellsworth - last year.

Sediment life

If the bacterium does belong to a new group, it will quickly come under scrutiny. "The next question is, where does it come from?" says Siegert. Researchers think life is most likely in the sediments at the lake bottom, where there is food. But if Bulat's bacterium came from the sediment in Lake Vostok, it must have been sucked up through 700 metres of lake water when the Russian drill head broke through the icy roof above Vostok.

"The only way to find out is to go into the lake itself and do direct sampling," says Siegert. Robots could collect lake water and sediment.

American researchers recently drilled into Lake Whillans, a shallower subglacial lake that is connected to a subglacial network of lakes and rivers, and also found living microbes.

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