Researchers Find Alga that Detoxify Arsenic

Arsenic may be tough, but scientists from Montana and Florida have found a Yellowstone National Park alga that's tougher.

The alga -- a simple one-celled algae called Cyanidioschyzon -- thrives in extremely toxic conditions and chemically modifies arsenic that occurs naturally around hot springs, said Tim McDermott, professor in the Department of Land Resources and Environmental Sciences at Montana State University.

The alga and how it detoxifies arsenic are described in a paper posted the week of March 9 in the online edition of Proceedings of the National Academy of Sciences, or PNAS. Lead authors are McDermott and Barry Rosen of Florida International University. Among the four co-authors is Corinne Lehr, who formerly worked with McDermott as a postdoctoral scientist at MSU and is now a faculty member at California Polytechnic State University.

Arsenic is the most common toxic substance in the environment, ranking first on the Superfund list of hazardous substances, the researchers wrote in their paper. McDermott said arsenic is very common in the hot, acidic waters of Yellowstone and presents real challenges for microorganisms living in these conditions. Indeed, there are challenges for the researchers. McDermott said the acid in the soil and water is strong enough that it sometimes eats holes through his jeans when he kneels to collect samples.

McDermott has worked in Yellowstone for more than a decade and travels year-round to the Norris Geyser Basin to study the microbial mats that grow in acidic springs. Over the years, he noticed thick algae mats that were so lush and green in December that they looked like Astro-Turf, McDermott said. By June, they were practically gone. While investigating the change, McDermott and his collaborators learned about the Cyanidiales alga and its ability to reduce arsenic to a less dangerous form.

The alga thrives in water up to 135 degrees Fahrenheit (too hot to shower) with a very acidic pH factor ranging from 0.5 to 3.5. Creeks are considered acidic if their pH factor is less than 7.

The scientists cloned genes from the alga, and then studied the enzymes to figure out how they transformed arsenic. They learned that the alga oxidizes, reduces, and converts arsenic to several forms that are less toxic than the original.

Rosen said one significant form is a gas that can evaporate, especially at the high temperatures of the Yellowstone springs. That allows life to exist in "really deadly concentrations of arsenic," he said.

McDermott said the scientists conducted basic research that may have implications someday for acid mine drainage and acid rock drainage remediation efforts.

Molecular evidence suggests that the algae in these springs are comprised of two different population groups, McDermott said. One flourishes in the winter and the other in the summer. The algae that dominate in the summer can tolerate high levels of ultraviolet rays.

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