Mercury-breathing bacteria might decontaminate crudely preserved Native American artifacts now in museums, speeding up the safe return of the stolen objects to their tribes.
Ceremonial masks, head dress, textiles and other artifacts were stolen from Native Americans as European settlers moved west across the continent. To keep insects and pests from ruining the objects, people – and later museums – doused them in heavy-metal pesticides.
“The mercury levels on these materials were unbelievable,” says Munira Albuthi, of the University of Colorado in Denver, who presented the research this week at the annual meeting of the American Society for Microbiology in Boston.
In 1990, the US government passed the Native American Graves Protection and Repatriation Act, mandating the return of the stolen relics. Museums then unknowingly returned objects chock full of mercury and arsenic.
“The high level of neurotoxins was making a lot of people crazy,” Albuthi says.
Museums have now put aside caches of thousands of mercury-tainted objects, awaiting decontamination. But the question is: how best to remove the toxic heavy metal?
Chemical washes, high heat or ultraviolet light could do the job. But those treatments are unacceptable to many tribes who see their ceremonial artifacts as living embodiments of their ancestors.
“To a lot of tribes, these things are alive,” says Albuthi. “You don’t want to do anything to them that you wouldn’t do to a relative.”
In search of a gentler treatment, Albuthi and her Denver colleague Timberley Roane proposed treating artifacts with naturally occurring soil bacteria that convert solid mercury pesticides into a mercury gas that can be sucked away.
To test this approach, the team designed a chamber that rains a mist of a mercury-resistant bacterium called Cupriavidus metallidurans that was previously isolated from museum artifacts.
They found that 10 days in the room-temperature incubator removed nearly all the mercury from filter paper spiked with levels of mercury far higher than those of the artifacts. Humidity alone removed 80% of the mercury, while the bacteria sopped up another 70% of the remaining heavy metal.
Next up, the researchers will try the technique on hair and feather, before move onto small samples of artifacts. But Roane and her colleagues are proceeding carefully before applying the bacteria to artifacts destined for repatriation.
She still doesn’t know whether the bacteria can remove mercury that has been in situ for years, and to makes thing more complicated many of the samples also have high levels of arsenic. “It’s kind of a wait and see situation,” she says.
Nancy Odegaard, a conservator at Arizona State Museum who has loaned artifacts to Roane’s team, says bacterial treatment looks promising. “The idea that an important cultural object could be cleaned – could be made culturally usable again – is very exciting.”
However, she says that efforts must proceed cautiously due to the artifacts’ cultural significance. “This isn’t your winter coat,” she adds.