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Tuckerfan
2009-Apr-17, 06:33 PM
Microbe found that breathes iron. (http://www.sciencedaily.com/releases/2009/04/090416144512.htm)
Chemical analysis of effluent from the inaccessible subglacial pool suggests that its inhabitants have eked out a living by breathing iron leached from bedrock with the help of a sulfur catalyst. Lacking any light to support photosynthesis, the microbes have presumably survived by feeding on the organic matter trapped with them when the massive Taylor Glacier sealed off their habitat an estimated 1.5 to 2 million years ago.

Mikucki, Pearson, and colleagues based their analysis on samples taken at Antarctica's Blood Falls, a frozen waterfall-like feature at the edge of the Taylor Glacier whose striking red appearance first drew early explorers' attention in 1911. Those "Heroic Age" adventurers speculated that red algae might have been responsible for the bright color, but scientists later confirmed that the coloration was due to rust, which the new research shows was likely liberated from subglacial bedrock by microorganisms.Gives us a clue to what potential alien life might be like, I'd think.

Swift
2009-Apr-17, 07:07 PM
Here (http://www.lpi.usra.edu/meetings/earlymars2004/pdf/8023.pdf) is the abstract from a 2004 presentation on what I assume was some earlier work on this.

This (http://www.eurekalert.org/pub_releases/2009-04/asu-ult041709.php) gives a little more/better explanation of the chemistry involved.

The research, which appears in the April 17 issue of Science, suggests that over the past 1.5 million years the microbes adapted to manipulate sulfur and iron compounds to survive. In place of photosynthesis, the microbes converted Fe(III) to Fe(II) to create food and energy.

....

The key piece of data supporting the hypothesis that the microbes were in fact surviving by turning Fe(III) to Fe(II) came from samples analyzed by Ariel Anbar, one of the authors of the study and an associate professor at Arizona State University, and researchers in his group, using instruments in the W. M. Keck Laboratory for Environmental Biogeochemistry at ASU.

"We found that the isotopes of Fe(II) in the brines are shifted in a way that is consistent with this microbial process," said Anbar, who holds joint appointments in the School of Earth and Space Exploration and the Department of Chemistry and Biochemistry in the College of Liberal Arts and Sciences.

Even the earliest explorers noted the massive red stain at the snout of the glacier and speculated as to what may have caused it. Some guessed that red alga was responsible for the bright color. "In fact, the red color is a result of all that Fe(II) produced by bacteria," said Anbar. "When the Fe(II)-rich water reaches the surface, the Fe(II) reacts with oxygen in the air to make Fe(III) compounds that are sort of like rust. That's the source of the red color."

The microbes are remarkably similar in nature to species found in marine environments, leading to the conclusion that the populations under the glacier are the remnants of a larger population of microbes that once occupied a fjord or sea that received sunlight. Many of these marine lineages likely declined, while others adapted to the changing conditions when the Taylor Glacier advanced, sealing off the system under a thick ice cap.

grant hutchison
2009-Apr-18, 12:10 AM
Canfield et al's Early anaerobic metabolisms (http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1664682) is a nice survey of the various anaerobic means bacteria use to obtain energy, including a section on iron-reducers.

Grant Hutchison