Science meets science fiction at the bottom of the sea
By Summit Voice
FRISCO — In the popular movie Avatar, the ecology of Pandora is shaped by a living neural network that connects all the living things, and now, a team of international scientists has discovered that the science fiction theme of the movie may not be so farfetched.
The scientists were studying bacteria living in marine sediments when they discovered what they described as a seemingly inexplicable electric current on the sea floor. The new experiments revealed that these currents are mediated by a hitherto unknown type of long, multicellular bacteria that act as living power cables.
“Until we found the cables we imagined something cooperative where electrons were transported through external networks between different bacteria. It was indeed a surprise to realize, that it was all going on inside a single organism,” said Lars Peter Nielsen of the Aarhus Department of Bioscience, and a corresponding author of the Nature paper, published Oct. 24.
Part of the bacteria live in a zone that is poor in oxygen but rich in hydrogen sulfide, part live in an area rich in oxygen but poor in hydrogen sulfide. To complete their life-sustaining reaction, the bacteria form long chains that transport individual electrons from the bottom to the top, generating life-sustaining energy.
The microscopic Desulfobulbus bacterial cells are only a few thousandths of a millimeter long, but they can transmit electrons across a distance as large as 1 centimeter as part of the filament’s respiration and ingestion processes.
“To move electrons over these enormous distances in an entirely biological system would have been thought impossible,” said Moh El-Naggar, assistant professor of physics at the USC Dornsife College of Letters, Arts and Sciences, and co-author of the Nature paper.
“You have feeder cells on one end and breather cells on the other, allowing the whole living cable to survive,” El-Naggar said.
Aarhus and USC researchers collaborated to use physical techniques to evaluate the long-distance electron transfer in the filamentous bacteria. El-Naggar and his colleagues had previously used scanning-probe microscopy and nanofabrication methods to describe how bacteria use nanoscale structures called “bacterial nanowires” to transmit electrons many body lengths away from cells.
“I’m a physicist, so when I look at remarkable phenomena like this, I like to put it into a quantifiable process,” El-Naggar said.
El-Naggar, who was just chosen as one of the Popular Science Brilliant 10 young scientists for his work in biological physics, said physicists are increasingly being tapped to tackle tough biological questions.
“This world is so fertile right now,” he said. “It’s just exploding.”