Silver-resistant bacteria

Although we think of silver as a bacteria fighter, a group of scientists in Sweden has found a bacterium that actually grows silver crystals and stores them on the edges of its cell wall.

This discovery is more than a scientific curiosity. It could lead to new techniques in recovering silver from ore, as well as growing super-thin, perhaps even elastic-like, silver crystals to specific shapes and sizes for use in electronics and optical applications.

“We intend to use these bacteria as living factories for the preparation and design of new materials,” says Tanja Klaus of the Uppsala University in Sweden (Dept. of Materials Science). “The films we are working on are wavelength-sensitive. You can collect light or energy coming from the sun in a specific range and [prevent that] energy from being emitted or lost. For example, you can make solar collectors and use them for water heating.”

The bacterium, Pseudomonas stutzeri, was originally found growing on rocks in silver mines. Klaus and her team were able to grow the bacteria in the laboratory and manipulate the shape in which they formed silver crystals. Most of the crystals were composed of nearly pure silver, but some were silver sulphide.

Klaus says the bacteria are clever in terms of how they store the silver crystals on the edges of the cell wall, so that the silver doesn’t enter the cell and destroy it (as silver normally does). In addition, she found that the bacteria can produce and store as much as 25% of the cell’s weight in silver. The next steps in Klaus’s research will concern improving the coatings by including higher silver content, controlling the properties of the silver particles and isolating the silver particles. “We are also investigating whether or not the material is suitable for further applications, such as electronic devices or carbon-based batteries.”

— The preceding is an excerpt from Silver News published by the Washington, D.C.-based Silver Institute.