More microbial diversity--here, there, everywhere...

I wrote previously about a recent study that found all sorts of bacterial diversity in a place once thought to be rather barren--the human stomach. One of the species they discovered appeared to be related to an extremophile--microbes that live in extreme environments (in this case, a relative of one that could withstand incredibly high doses of radiation). A new story from the BBC reports the discovery of another extremophile in a place one may not expect it (or at least, may not expect the one they found):

Researchers have found traces of a heat-loving bacterium that may live beneath a frozen lake in Antarctica.

Lake Vostok is covered by more than 3km of ice and must have been isolated from our planet's atmosphere for millions of years.

The bacteria appeared in sediment mixed with a core of ice drilled by Russian and French researchers.

The heat-loving, or thermophilic, bacterium may suggest that hydrothermal vents exist on the lake floor.

*snip*

So far they have found no definitive traces of life within Lake Vostok. But the ice also contained streaks of dark sediment that they believe was thrust up from the lake floor by a small earthquake.

In the sediment, the team found genetic traces of a bacterium that usually lives in temperatures of 50-60C.

"We expected to find life adapted to a cold environment but instead we found exactly the opposite," said Jean-Robert Petit of the Laboratory of Glaciology and Geophysics of the Environment in Grenoble, France.

A big problem with studies such as these--especially when they find microbes that are polar opposites from what they expected--is contamination. According to the story, however, the lab hadn't previously worked with the species that they identified in the ice samples, and the microbe is rare, so that makes contamination less likely.

In addition to learning more about what's going on here on earth, these types of extreme environments are often used as a proxy to examine what type of microbial life may exist elsewhere in the universe.

Because Vostok sees no sunlight and has not been in contact with the atmosphere since it was covered with ice around 15 million years ago, scientists hope it might reveal the kind of life that could exist on other planets, or on Europa, the ice-covered moon of Jupiter.

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I had spent a few weeks teaching undergrads about petroleum generation and had stumbled across this neat article:

http://www.nature.com/nature/journal/v426/n6964/full/nature02134.html

It talks about bacterial degradation of oil up to 80 degrees Celcius, several kilometres deep in the earth.

The hydrocarbon-generating window in the crust is about 75 to 225 degrees C, more or less, which takes a few kilometres of burial to reach in most cases. Early in the burial history of organic matter, before temperatures rise to where it is in the hydrocarbon window, anaerobic bacteria feast on organic deposits. The bacteria incorporate the organic matter into themselves and when they die they become part of the organic stockpile from which petroleum will be generated at higher temperatures.

Later, after deeper burial of the source rock and time spent in the hydrocarbon-generating window, petroleum has been generated and it migrates out. The oil will gradually migrate its way upwards through whatever route is available into cooler, shallower rocks where bacteria can once again attack it. The tar sands of Alberta are found in the very shallow subsurface and have been attacked by bacteria and groundwater for millions of years, creating a highly degraded and tar-like hydrocarbon deposit.

Extremophiles are kewl.

By Miguelito (not verified) on 10 Apr 2006 #permalink

But are those thermophils alive today, or could their DNA have been preserved in ice for millions of years?

Good question. As far as I can tell, all they have is their DNA, so I'm not sure about the contemporary relatives.

Miguelito, cool study--thanks!

A thermophile in the Antarctic is quite interesting. My lab advisor would be quite interested in that. We've studied thermophiles from deep gold mines in Africa to determine their DNA repair systems. I'm currently looking at phage that infect halophiles.