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Bacteria have found a new vocation - as nanoscale construction workers. Such bugs might form microbial machines that could repair wounds or build microscopic electrical circuits.
Tetsuo Kondo of the Forestry and Forest Products Research Institute in Ibaraki, and his colleagues, used a grooved film to train the bacterium Acetobacter xylinum to exude neat ribbons of a biological building material - cellulose1. The bug laid down strips at a rate of 4,000ths of a millimetre per minute.
If the method can be extended to other materials, bacterial builders running on templates could find medical applications, such as healing wounds, says Kondo. "Devices holding nanomachines could regenerate skin," he suggests.
"It sounds entertaining," says nanotech researcher Paul Alivisatos of the University of California at Berkeley. There are many ways to build nanoscale structures, he says, such as etching or using self-assembling molecules. "But new ones are always welcome."
Cellulose is not an ideal building material, however, as it is biodegradable. So Kondo's team are tinkering with the bugs' genetic make-up, so that they secrete alternative sugar molecules that might be more resistant to degradation.
Kondo built the grooved template by chemically precipitating cellulose tracks - less than a nanometre apart - onto a copper base. Although these tracks are tiny, the bugs are able to build up larger cellulose fibres spanning several lanes of track.
As the bacteria squeeze out cellulose from their back ends, they drive themselves forward. The cellulose template acts as a "nano-anchor" for the secreted fibres, explains Kondo.
Because the builder-bugs can only work in a liquid growth medium, Kondo suggests that the width of the bacterial building could be easily controlled by altering the area of the track covered by media.
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