When Yuri Gorby discovered that a microbe which transforms toxic metals can sprout tiny electrically conductive wires from its cell membrane, he reasoned this anatomical oddity and its metal-changing physiology must be related.
A colleague who had heard Gorby's presentation at a scientific meeting later reported that he, too, was able to coax nanowires from another so-called metal-reducing bacteria species and futher suggested the wires, called pili, could be used to bioengineer electrical devices.
It now turns out that not only are the wires and their ability to alter metal connected--but that many other bacteria, including species involved in fermentation and photosynthesis, can also form wires under a variety of environmental conditions.
"Earth appears to be hard-wired," said Gorby, staff scientist at the Department of Energy's Pacific Northwest National Laboratory, who documents the seeming ubiquity of electrically conductive microbial life in the July 10 advance online Proceedings of the National Academy of Science.
In a series of experiments, Gorby and colleagues induced nanowires in a variety of bacteria and demonstrated that they were electrically conductive. The bacterial nanowires were as small as 10 nanometers in diameter and formed bundles as wide as 150 nanometers. They grew to be tens of microns to hundreds of microns long.
The common thread involved depriving a microbe of something it needed to shed excess energy in the form of electrons. For example, Shewanella, of interest in environmental cleanup for its ability to hasten the weathering of toxic metals into benign ones, requires oxygen or other electron acceptors for respiration, whereas Synechocystis, a cyanobactetrium, combines electrons with carbon dioxide during photosynthesis.
Bereft of these "electron acceptors," bacterial nanowires "will literally reach out and connect cells from one to another to form an electrically integrated community," Gorby said.
"The physiological and ecological implications for these interactions are not currently known," he said, "but the effect is suggestive of a highly organized form of energy distribution among members of the oldest and most sustainable life forms on the planet."
In one clever twist, Gorby grew pili from mutant strains developed by collaborators that were unable to produce select electron transport components called cytochromes. Sure enough, the nanowires of the mutants were poor conductors.
"These implicate cytochromes as the electrically conductive components of nanowires, although this has yet to be conclusively demonstrated," Gorby said.
To measure currents as precisely as possible, Gorby and colleagues from the University of Southern California have built a microbial fuel cell laboratory at PNNL. The small bacteria-powered batteries, cultured under electron-acceptor limitations and fueled by lactate or light, now produce very little power, as measured by a voltmeter hooked to a laptop computer.
Co-author and PNNL scientist Jeff Mclean, who manages the microbial fuel cell laboratory, said that small changes in fuel cell design and culture conditions have already shown large improvements in the efficiency of the fuel cells. For example, so-called biofilms--a highly interconnected bacterial community--put out much more energy than other configurations.
Bill Cannon | EurekAlert!
Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery
20.01.2017 | GSI Helmholtzzentrum für Schwerionenforschung GmbH
Seeking structure with metagenome sequences
20.01.2017 | DOE/Joint Genome Institute
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
20.01.2017 | Awards Funding
20.01.2017 | Materials Sciences
20.01.2017 | Life Sciences