New Mexico Mineral Symposium — Abstracts

We usually don't think of microbes in the same context with minerals. Microbes (bacteria, algae, fungi) are ubiquitous on (and in) our planet. But for the most part, we know very little about what they do, other than the small percentage that make us ill, like anthrax. Even the scientific community has had a very limited understanding of these marvelous little critters outside of the laboratory. In fact, a whole new branch of life, the archaea, was only just discovered in the 1980s. Because they could not be cultured in the lab, no one knew they existed until the tool of DNA analysis was invented. We are now making amazing discoveries in the world around us: the archaea may comprise over 95% of the biomass in the world's oceans.' Indigenous living organisms have been found deep into the earth's crust, in the deepest gold mines in South Africa for example, when only a few decades ago it was believed that microorganisms could not survive deeper than a few meters into the earth' Scientists have speculated that microbial life may extend many kilometers into the earth's crust and that the biomass there may far exceed that of all other life'.

It is becoming increasingly clear that many of the mineral-forming processes are influenced, to some extent, by microbial action. Bacteria can process nearly every element in the periodic table. They can precipitate sulfur from hydrogen sulfide gas, fix arsenic from ground water, reduce gypsum into elemental sulfur and calcite, or precipitate volumes of oxides from minute quantities of manganese present in seawater. Microbes do these things in order to provide themselves with energy and nutrients or to sequester toxic elements such as heavy metals out of harms way. Furthermore, they can live happily in the most hostile environments: precipitating calcium carbonate from boiling hot springs in Yellowstone, corroding stainless pipes inside nuclear reactors, or forming metal sulfides at thousands of meters depth in the ocean.

There is a growing collection of information about the ability of microbes to directly precipitate minerals, or certainly to cause the indirect formation of minerals. Some examples of minerals or mineral environments that may result from microbial activity:

• Agates
• Fossil bone & other fossilized material
• Manganese nodules
• Banded iron formations
• Cave speleothems
• Travertine

There is even evidence that bacteria may be responsible for gold accumulation in some placer deposits 4'S With the knowledge that microbes can act upon most elements, there are new applications being developed that utilize microbial communities to extract ore, clean up waste, and to remediate toxic waste sites and spills. In addition, a question that many researchers are trying to answer is whether there are certain minerals that can help us determine if there is life elsewhere in the solar system.

The search for life on Mars will begin in the subsurface of Earth.6 Researchers at the University of New Mexico and New Mexico Tech are studying caves in Carlsbad Caverns National Park because they represent unique environments at the interface between the microbial world and the realm of minerals. The researchers have discovered unique microorganisms that live deep in Lechuguilla Cave, dissolving limestone to release iron and manganese that are then oxidized as an energy source. The oxides accumulate into thick deposits on the cave walls, ceilings, and floors. Minerals include iron oxides (lepidocrosite, goethite, hematite) and manganese oxides (todorokite and lithiophorite), which may be the direct result of microbial activity. There are also more usual minerals whose origin is less certain, such as nordstadite (aluminum-hydroxide) and svanbergite (aluminum-strontium sulfate-phosphate). Another line of research involves some of the unusual mineral forms that decorate Carlsbad Caverns and Lechuguilla Caves, among others. These forms, called moonmilk, pool fingers, and U-loops, were deposited on and around microbial filaments deep in the caves.

References:

1. 1Fuhrman, K. A., McCallum, K., and Davis, A. A., 1992, Novel major Archaebacterial group from marine plankton: Nature, v. 356, no. 6365, pp. 148-149.
2. 2Takai, K., Moser, D. P., DeFlaun, M., Onstott, T. C., Fredrickson, J. K., 2001, Archaeal diversity in waters from deep South African gold mines: Applied and Environmental Microbiology, v. 67, no. 12, pp. 5750-5760.
3. 3Gold, T., 1997, An unexplored habitat for life in the universe?: American Scientist, v. 85, Sept/Oct, pp. 408-411.
4. 4Southam, G., and Beveridge, T. J., 1996, The occurrence of sulfur and phosphorous within bacterially derived crystalline and pseudocrystalline gold formed in vitro: Geochimica et Cosmochimica Acta, v. 60, no. 22, pp. 4369-4376.
5. 5Eyles, N., 1995, Characteristics and origin of coarse gold in late Pleistocene sediments of the Caribo placer mining district, British Columbia, Canada: Sedimentary Geology, v. 95, no. 1-2, pp. 69-95.
6. 6Boston, P. J., Spilde, M. N., Northup, D. E., Melim, L. A., Soroka, D. S., Kleina, L. G., Lavoie, K. H., Hose, L. D., Mallory, L. A., Dahm, C. N., Crossey, L. J., and Schelble, R. T., 2001, Cave biosignature suites???microbes, minerals, and Mars: Astrobiology Journal, v. 1, no. 1, pp. 25-55.