Microbes clean up mercury

BOSTON — In a sequel to the smallpox-contaminated blankets hand out, museums inadvertently began another round of toxic giving to Native Americans in the 1990s — returning headdresses and other artifacts that were laced with mercury. Now scientists are looking to a microbe that converts mercury into a form that evaporates, with hopes of cleaning up the artifacts before giving back more of them to their rightful tribes.

“Do we give them something covered in mercury just to have given them their things back? No — it is not OK,” says Munira Albuthi, a microbiologist at the University of Colorado Denver who did the research to see if such a microbial method is possible. “Mercury is a potent neurotoxin.”

The neurotoxic effects of headgear laced with mercury had been recognized anecdotally for years. At Alice’s tea party, the Mad Hatter wasn’t angry — he was crazy from wearing and working with hats, which used to be cured with mercury.

The 1990 Native American Graves Protection and Repatriation Act required federal agencies and institutions to return Native American cultural items and remains to their respective peoples. But when museums began giving back ceremonial head gear and other artifacts, many of the recipients ended up ill. The specimens were laced with mercury, a component of the pesticides that museums had used for years for preservation.

Once the problem of the poisoned artifacts was recognized, scientists had to figure out a culturally sensitive means of getting rid of the toxin.

“A lot of tribes see these artifacts as live spirits — these are relatives to a lot of people,” says Albuthi, who presented the work in Boston at the 108th meeting of the American Society for Microbiology. “So we needed to use something you would be OK with using on yourself.”

Albuthi began working with Cupriavidus metallidurans, a microbe that flourishes on metal and is not dangerous to humans. It has a set of proteins that turns mercury into a form that evaporates into the air. After contaminating paper, a watery broth and auger plates with the neurotoxin, she used a pipette to put the bacterium onto the items. Seven days later, 40 percent of the mercury had been removed from the broth, 50 percent was removed from the auger plates and 60 percent was removed from the paper. Because paper is porous and organic, it is most like the specimens that museums are dealing with, she notes.

Albuthi also investigated whether different temperatures or humidities enhanced the microbes’ mercury-morphing powers. She found that the microbes worked best at room temperature and 60 percent humidity, with about 80 percent of the mercury evaporated from the items.

The experiments used mercury concentrations of 10 parts per million, which are much higher than the quantities on most museum specimens, says Albuthi. “So maybe we’ll be able to get 100 percent, if there isn’t as much to begin with,” she says.

“This is a very interesting and particularly challenging project. They were very constrained in terms of what they could treat things with,” comments Gregory Hecht, a microbiologist at RowanUniversity in Glassboro, N. J. “And microbes are probably the best way to get around the issue.”