[meteorite-list] Underground Bacteria

Thu Oct 26 08:06:50 EDT 2006

Apologies if this was posted earlier - I may have missed it.

http://www.princeton.edu/main/news/archive/S16/13/72E53/index.xml?section=newsreleases

Abstract

Long-Term Sustainability of a High-Energy, Low-Diversity Crustal Biome

By Li-Hung Lin, Pei-Ling Wang, Douglas Rumble, Johanna Lippmann-Pipke, Erik 
Boice, Lisa M. Pratt, Barbara Sherwood Lollar, Eoin L. Brodie, Terry C. 
Hazen, Gary L. Andersen, Todd Z. DeSantis, Duane P. Moser, Dave Kershaw, and 
T. C. Onstott

Geochemical, microbiological, and molecular analyses of alkaline saline 
groundwater at 2.8 kilometers depth in Archaean metabasalt revealed a 
microbial biome dominated by a single phylotype affiliated with thermophilic 
sulfate reducers belonging to Firmicutes. These sulfate reducers were 
sustained by geologically produced sulfate and hydrogen at concentrations 
sufficient to maintain activities for millions of years with no apparent 
reliance on photosynthetically derived substrates.

News Releases
All News Releases | « Previous News Release | Next News Release » For 
immediate release: October 20, 2006
Media contact: Chad Boutin, (609) 258-5729, cboutin at princeton.edu
Two miles underground, strange bacteria are found thriving
A Princeton-led research group has discovered an isolated community of 
bacteria nearly two miles underground that derives all of its energy from 
the decay of radioactive rocks rather than from sunlight. According to 
members of the team, the finding suggests life might exist in similarly 
extreme conditions even on other worlds.

The self-sustaining bacterial community, which thrives in nutrient-rich 
groundwater found near a South African gold mine, has been isolated from the 
Earth's surface for several million years. It represents the first group of 
microbes known to depend exclusively on geologically produced hydrogen and 
sulfur compounds for nourishment. The extreme conditions under which the 
bacteria live bear a resemblance to those of early Earth, potentially 
offering insights into the nature of organisms that lived long before our 
planet had an oxygen atmosphere.

The scientists, who hail from nine collaborating institutions, had to burrow 
2.8 kilometers beneath our world's surface to find these unusual microbes, 
leading the scientists to their speculations that life could exist in 
similar circumstances elsewhere in the solar system.

"What really gets my juices flowing is the possibility of life below the 
surface of Mars," said Tullis Onstott, a Princeton University professor of 
geosciences and leader of the research team. "These bacteria have been cut 
off from the surface of the Earth for many millions of years, but have 
thrived in conditions most organisms would consider to be inhospitable to 
life. Could these bacterial communities sustain themselves no matter what 
happened on the surface? If so, it raises the possibility that organisms 
could survive even on planets whose surfaces have long since become 
lifeless."

Onstott's team published its results in the Oct. 20 issue of the journal 
Science. The research group includes first author Li-Hung Lin, who performed 
many of the analyses as a doctoral student at Princeton and then as a 
postdoctoral researcher at the Carnegie Institution.

"These bacteria are truly unique, in the purest sense of the word," said 
Lin, now at National Taiwan University. "We know how isolated the bacteria 
have been because analyses of the water that they live in showed that it's 
very old and hasn't been diluted by surface water. In addition, we found 
that the hydrocarbons in the environment did not come from living organisms, 
as is usual, and that the source of the hydrogen needed for their 
respiration comes from the decomposition of water by radioactive decay of 
uranium, thorium and potassium."

Because the groundwater the team sampled to find the bacteria comes from 
several different sources, it remains difficult to determine specifically 
how long the bacteria have been isolated. The team estimates the time frame 
to be somewhere between three and 25 million years, implying that living 
things are even more adaptable than once thought.

"We know surprisingly little about the origin, evolution and limits for life 
on Earth," said biogeochemist Lisa Pratt, who led Indiana University 
Bloomington's contribution to the project. "Scientists are just beginning to 
study the diverse organisms living in the deepest parts of the ocean, and 
the rocky crust on Earth is virtually unexplored at depths more than half a 
kilometer below the surface. The organisms we describe in this paper live in 
a completely different world than the one we know at the surface."

That subterranean world, Onstott said, is a lightless pool of hot, 
pressurized salt water that stinks of sulfur and noxious gases humans would 
find unbreathable. But the newly discovered bacteria, which are distantly 
related to the Firmicutes division of microbes that exist near undersea 
hydrothermal vents, flourish there.

"The radiation allows for the production of lots of sulfur compounds that 
these bacteria can use as a high-energy source of food," Onstott said. "For 
them, it's like eating potato chips."

But the arrival of the research team brought one substance into the 
underground world that, though vital to human survival, proved fatal to the 
microbes -- air from the surface.

"These critters seems to have a real problem with being exposed to oxygen," 
Onstott said. "We can't seem to keep them alive after we sample them. But 
because this environment is so much like the early Earth, it gives us a 
handle on what kind of creatures might have existed before we had an oxygen 
atmosphere."

Onstott said that many hundreds of millions of years ago, some of the first 
bacteria on the planet may have thrived in similar conditions, and that the 
newly discovered microbes could shed light on research into the origins of 
life on Earth.

"These bacteria are probably close to the base of the tree for the bacterial 
domain of life," he said. "They might be genealogically quite ancient. To 
find out, we will need to compare them to other organisms such as Firmicutes 
and other such heat-loving creatures from deep sea vents or hot springs."

The research team is building a small laboratory 3.8 kilometers beneath the 
surface in the Witwatersrand region of South Africa to conduct further study 
of the newly discovered ecosystem, said Onstott, who hopes the findings will 
be of use when future space probes are sent to seek life on other planets.

"A big question for me is, how do these creatures sustain themselves?" 
Onstott said. "Has this one strain of bacteria evolved to possess all the 
characteristics it needs to survive on its own, or are they working with 
other species of bacteria? I'm sure they will have more surprises for us, 
and they may show us one day how and where to look for microbes elsewhere."

Other authors of this work include Johanna Lipmann-Pipke of 
GeoForschungsZentrum, Potsdam, Germany; Erik Boice of Indiana University; 
Barbara Sherwood Lollar of the University of Toronto; Eoin L. Brodie, Terry 
C. Hazen, Gary L. Andersen and Todd Z. DeSantis of Lawrence Berkeley 
National Laboratory, Berkeley, Calif.; Duane P. Moser of the Desert Research 
Institute, Las Vegas; and Dave Kershaw of the Mponeng Mine, Anglo Gold, 
Johannesburg, South Africa.

Pratt and Onstott have collaborated for years as part of the 
Indiana-Princeton-Tennessee Astrobiology Institute (IPTAI), a NASA-funded 
research center focused on designing instruments and probes for life 
detection in rocks and deep groundwater on Earth during planning for 
subsurface exploration of Mars. IPTAI's recommendations to NASA will draw on 
findings discussed in the Science report.

This work was also supported by grants from the National Science Foundation, 
the U.S. Department of Energy, the National Science Council of Taiwan, the 
Natural Sciences and Engineering Research Council of Canada, Deutsche 
Forschungsgemeinschaft (DFG, German Research Foundation) and the Killam 
Fellowships Program.

More information about the discovery can be found at 
http://newsinfo.iu.edu/news/page/normal/4229.html and 
http://www.carnegieinstitution.org/news_releases/news_2006_1019.html

http://www.princeton.edu/main/news/archive/S16/13/72E53/index.xml?section=newsreleases

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