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"Microbe vs. Mineral - A Life and Death Struggle in the Desert"

A crushed salt sample with water added reveals microscopic microbial life

"Microbe vs. Mineral - A Life and Death Struggle in the Desert," by Michael P. Zach, University of Wisconsin-Stevens Point.

Although the bursts of rainbow colors in this photograph are mesmerizing, microbes fight for their lives in the background. Zach, a chemist, snapped this image of a salt sample he collected in a hot, arid valley near Death Valley National Park in California. He crushed the salt, placed it under a microscope slide and added a drop of water. Suddenly a slew of microbes came to life as the salt crystals dissolved. Then when the water started evaporating, he took a picture. The colors come from light passing through the growing crystals, which act like prisms.

The small specks in the background are living halophilic bacteria. The rainbow crystal clusters form as the water evaporates and may eventually overgrow the bacteria. Organic materials are known to adhere to mineral surfaces, thus sealing the crystal surface from further growth. If the microbes have not produced enough organic material to coat and inhibit crystal growth, they could be trapped within the growing crystals. If that happens, they would be trapped until the next rainy season or perhaps.the next million years until a cosmic ray "does them in." But if the microbes produce the right adsorbates and in sufficient quantities to inhibit the crystal growth, they can continue to live and reproduce in a supersaturated brine solution. Zach says the life and death struggle between microbes and the interruption of the normal crystallization process is just one puzzle that he finds so interesting about the connection between microbes and minerals. This image hints at the power that nature has to help solve some of the materials engineering problems that our society faces with both corrosion and scale formation.

This image won Honorable Mention in the Photography category of the 2009 International Science & Engineering Visualization Challenge (SciVis) competition, sponsored by the National Science Foundation and the journal Science. The competition is held each year to celebrate the grand tradition of science visualization and to encourage its continued growth. The spirit of the competition is to communicate science, engineering and technology for education and journalistic purposes. To learn more about the competition and view all the winning entries, see the NSF SciVis Special Report. (Date of Image: October 2002)

Credit: Michael P. Zach, Chemistry Department, University of Wisconsin-Stevens Point
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