When the researchers cut the nanowire, the flow of current stopped.
Previous studies showed that electrons could move across a nanowire, which did not prove that nanowires conducted electrons along their length.
El-Naggar's group is the first to carry out this technically difficult but more telling experiment.
Electricity carried on nanowires may be a lifeline. Bacteria respire by losing electrons to an acceptor for Shewanella, a metal such as iron. (Breathing is a special case: Humans respire by giving up electrons to oxygen, one of the most powerful electron acceptors.)
Nealson said of Shewanella: "If you don't give it an electron acceptor, it dies. It dies pretty rapidly."
In some cases, a nanowire may be a microbe's only means of dumping electrons.
When an electron acceptor is scarce nearby, nanowires may help bacteria to support each other and extend their collective reach to distant sources.
The researchers noted that Shewanella attach to electron acceptors as well as to each other, forming a colony in which every member should be able to respire through a chain of nanowires.
"This would be basically a community response to transfer electrons," El-Naggar explained. "It would be a form of cooperative breathing."
El-Naggar and his team are among the pioneers in a young discipline. The term "bacterial nanowire" was coined in 2006. Fewer than 10 studies on the subject have been published, according to co-author Yuri Gorby of The J. Craig Venter Institute in San Diego, discoverer of nanowires in Shewanella.
Gorby and others became interested in nanowires when they noticed that reduction of metals appeared to be occurring around the filaments. Since reduction requires the transfer of electrons to a metal, the researchers suspected that the filaments were carrying
|Contact: Carl Marziali|
University of Southern California