New Life for Native Artifacts

Researchers investigate the use of bacteria to detoxify American Indian artifacts

Roane (left) and Nancy Odegaard (right), conservator and head of preservation at the Arizona State Museum, assess an artifact in the cleaning study.

Say the word bacteria and images of sickness, disease and germs quickly come to mind. However, recent research reveals bacteria may be the biggest ally in the fight to preserve ancient artifacts from erosion and deterioration.

Timberley Roane, associate professor of Biology at the University of Colorado Denver (UCD) has been working on ways to safely remove harmful chemicals from artifacts under a grant from NCPTT.

“Early methods of preserving many native artifacts, such as headdresses, pipes, blankets and ceremonial masks, relied heavily on the use of pesticides,” Roane said. “Two common ingredients in those pesticides were mercury and arsenic. Concentrations of those chemicals now make it risky for humans to come into contact with the artifacts.”

A researcher collects mercury resistant bacteria from the surface of an artifact. In the top panel, a sterile swab is used to gently wipe the surface of the artifact to transfer surface bacteria to the swab.

Inhaling or exposing skin to artifacts contaminated with mercury can be very dangerous, and can make handling such artifacts difficult. Roane’s approach is to use bacteria to change the mercury into a gaseous form which then can be disposed of safely.

“These bacteria may be the key to helping return artifacts to the cultures that created them and to return them without endangering individuals coming in contact with the items,” she said.

Since beginning her research Roane has conducted bacterial evaluations on mercury-treated materials such as paper, agar, broth, human and horse hair. A treatment chamber was designed to control temperature and humidity during bacterial treatment and provide containment for the gaseous by-product.

“Temperature and humidity are two major factors that can influence bacterial growth and therefore potentially the rates of mercury removal. As such, we want to control the temperature and humidity for treatment efficiency,” she said.

Finding the proper method of bacteria application took some trial and error. Various techniques, including wet application of bacterial suspensions, micro-droplet application via high frequency sound waves, and application via a nebulizer were attempted.

Of these three processes, the nebulizer application appeared to be the most effective in terms of keeping the material dry, achieving an even coat of bacteria, maintaining bacterial viability, and being easy to use within the bacterial application chamber.

The bacteria collected on the swab are then transferred to a petri dish containing a bacterial growth medium.

While experimental efforts have shown the effectiveness of some bacteria in removing mercury, the project has faced its share of obstacles. Among them: finding non-chemically treated wool. Commercially available wool, used in cloth material, is treated with a variety of preservatives and dyes.

“We do not yet know how the dyes and preservatives in commercial wool will influence the bacterial removal of mercury,” Roane said. “We are currently setting up the wool studies but we will be working with untreated wool initially in order to establish a starting point for removal. We will need to ultimately address removal from treated fabrics, such as wool and cotton.”

Roane plans to conclude her research in 2009. The final report will be available for download on the NCPTT website.