Biological wires carry electricity thanks to special amino acids

Slender bacterial nanowires require certain key amino acids in order to conduct electricity, according to a study to be published in mBio, the online open-access journal of the American Society for Microbiology, on Tuesday, March 12. In nature, the bacterium…

Slender bacterial nanowires require certain key amino acids in order to conduct electricity, according to a study to be published in mBio, the online open-access journal of the American Society for Microbiology, on Tuesday, March 12.

In nature, the bacterium Geobacter sulfurreducens uses these nanowires, called pili, to transport electrons to remote iron particles or other microbes, but the benefits of these wires can also be harnessed by humans for use in fuel cells or bioelectronics. The study in mBio reveals that a core of aromatic amino acids are required to turn these hair-like appendages into functioning electron-carrying biological wires.

“It’s the aromatic amino acids that make it a wire,” says lead author Derek Lovley of the University of Massachusetts, Amherst. Lovley and his colleagues removed the pivotal amino acids from the pili and replaced them with smaller, non-aromatic amino acids. Without these key components, Lovley says, the pili are nothing more than protein strings. “We showed it’s not good enough to just make the string – you’ve got to make a wire,” says Lovley.

G. sulfurreducens “breathes” by removing electrons from organic materials and funneling them to iron oxides or to other microorganisms, much the way humans pull electrons out of organic molecules in food and dump them on oxygen. The bacteria use their pili to reach out to iron oxides or other microbes, transferring the “waste” electrons along the structure to the destination. Geobacter’s pili are only 3-5 nanometers wide, but they can be 20 micrometers long, many times longer than the cell itself.
Trafficking in electrons is how all living things breathe, but it is normally carried out by discrete proteins or other molecules that act like containers for shuttling electrons from one place to another. Lovley says earlier results showed the pili in G. sulfurreducens possess metallic-like conductivity, the ability to carry electrons along a continuous structure, a controversial finding in biology.
To investigate how pili accomplish this singular feat, Lovley says they looked to non-biological organic materials that can conduct electricity. “In those synthetic materials, it’s aromatic compounds that are responsible for the conductivity. We hypothesized that maybe it’s similar in the Geobacter pili. In this case, it would be aromatic amino acids.” Aromatic compounds have a highly stable ring-shaped structure made of carbon atoms.
Turning to the pili, Lovley says his group looked for aromatic amino acids in the parts of the pili proteins that would most likely contribute to the conductivity. Using genetic techniques, they developed a strain of Geobacter that makes pili that lack aromatic amino acids in these key regions, then they tested whether these pili could still conduct electricity. They could not. Removing the aromatic amino acids was a bit like taking the copper out of a plastic-covered electrical wire: no copper means no current, and all you’re left with is a string.
Removing aromatic amino acids from the pili prevents the bacteria from reducing iron, too, says Lovley, an important point because it adds further proof that Geobacter uses its pili as nanowires for carrying electrons to support respiration.
Metal reducers like Geobacter show a lot of promise for use in fuel cells, says Lovley, and by feeding electrons to the microbes that produce the methane, they’re an important component of anaerobic digesters that produce methane gas from waste products. Understanding how they shuttle their electrons around and how to optimize the way the pili function could lead to better technologies.
Moving forward, Lovley says his own lab plans to explore the possibilities of biological nanowires, exploring how to make them more or less conductive.

Journal reference:

mBio

Provided by

American Society for Microbiology

view popular
send feedback to editors

not rated yet

1
2
3
4
5

Rank

1
2
3
4
5

not rated yet

more news

Related Stories

Sep 07, 2009
0
Making more efficient fuel cells

Sep 06, 2011
0
Researchers discover how bacteria can immobilize uranium

Jul 28, 2009
0
Researchers Develop New Geobacter Microbe Strain to Produce More Electricity, Open New Applications

Aug 07, 2011
0
Research team discovers new conducting properties of bacteria-produced wires

Relevant PhysicsForums posts

L’Methyl Folate
7 hours ago
Does anyone have any references for me with good information on the genes (don’t even know their names) responsible for the synthesizing of L’methyl folate from folic acids. Also I’d like to learn…

[Ecology] I think I’m nuts about ecology
Mar 10, 2013
As an aspirant scientist, physicist to be more precise, I believe it would be “normal” to be an ecologist. In fact I’ve always taken care of the Earth in my life since I’ve been taught to be…

Why would I need so much knowledge for a general ecology course?
Mar 10, 2013
So I would like to do an ecology course somewhen during my undergrad, but the requisites for a General Ecology are just too big:

-1 year in Zoology and Botany
-1 year in General Biology (in order…

Hemoglobin S Trait
Mar 10, 2013
If a person is a carrier for sickle cell disease or has hemoglobin AS, then does this mean that the carrier is not affected by hemoglobinopathy? (He/she is normal/healthy?)

Thank you.

‘New Bacteria’ found in Antarctic Lake
Mar 07, 2013
http://news.discovery.com/earth/russia-finds-new-bacteria-antarctic-lake-130307.htm

—-Quote—-
Russian scientists believe they have found a wholly new type of bacteria in the subglacial Lake…

Understanding a graph. Have Ambyplygi evolved from spiders?
Mar 07, 2013
I’m trying to understand the tree-graph on the right side of http://en.wikipedia.org/wiki/Arachnid#Systematics.
If I understand well, Opiliones evolved from scorpions, ambyplygi evolved from spiders…

More from Physics Forums – Biology

More news stories

Scientists identify why some fathers are left holding the baby

A century old mystery as to why, for some animals, it’s the father rather than the mother that takes care of their young has been cracked by scientists at the University of Sheffield and University of Bath.

Biology / Plants & Animals

9 hours ago |
4.2 / 5 (5) |
2
|

What can ‘ring species’ teach us about evolution?

Ten thousand years ago, at the end of the last ice age, a species of greenish warblers lived in a forest south of the Tibetan Plateau. As the ice receded, the forest grew to form a ring around the plateau—and so did the …

Biology / Ecology

9 hours ago |
4.8 / 5 (4) |
2
|

Cryptic clams: Biologists find species hiding in plain view

Cryptic comments seem to have an ambiguous, obscure or hidden meaning. In biology, cryptic species are outwardly indistinguishable groups whose differences are hidden inside their genes.

Biology / Ecology

9 hours ago |
4.5 / 5 (2) |
1
|

Marine diversity study proves value of citizen science

Citizen science surveys compare well with traditional scientific methods when it comes to monitoring species biodiversity – according to new research from the University of East Anglia.

Biology / Ecology

2 hours ago |
not rated yet |
0

Study shows urban noise leads to less songbird diversity

(Phys.org) —A team of Canadian researchers has found that anthropogenic noise (noise created by people that impacts other species) in urban areas leads to less songbird diversity. In their paper published …

Biology / Ecology

10 hours ago |
not rated yet |
0
|

Cancer researchers discover new type of retinoblastoma in babies

A team of Canadian and international cancer researchers led by Dr. Brenda Gallie at the Princess Margaret Cancer Centre, University Health Network (UHN), has discovered a new type of retinoblastoma, a rapidly developing eye …

Medicine & Health / Cancer
1 hour ago |
not rated yet |
0

Flexible, semitransparent power source made with novel comb-teeth structure

(Phys.org) —Most batteries, supercapacitors, and other energy storage devices are based on a sandwich structure, where two electrodes face each other and the charge flows between them. However, when these …

Nanotechnology / Nanophysics
8 hours ago |
4.8 / 5 (5) |
0
|

Curiosity rover finds conditions once suited for ancient life on Mars

(Phys.org) —An analysis of a rock sample collected by NASA’s Curiosity rover shows ancient Mars could have supported living microbes.

Space & Earth / Space Exploration
7 hours ago |
4.8 / 5 (13) |
4
|

Astrobiologists claim meteorite carried space algae

(Phys.org) —A fireball that appeared over the Sri Lankan province of Polonnaruwa on December 29, 2012 was a meteorite containing algae fossils, according to a paper published in the Journal of Cosmology. A team …

Space & Earth / Space Exploration
9 hours ago |
3.1 / 5 (11) |
15
|

When hungry, Gulf of Mexico algae go toxic

When Gulf of Mexico algae don’t get enough nutrients, they focus their remaining energy on becoming more and more poisonous to ensure their survival, according to a new study by scientists from North Carolina …

Space & Earth / Environment
4 hours ago |
5 / 5 (2) |
0
|

Fertility after ectopic pregnancy: Study finds reassuring evidence on different treatments

The first randomised trial to compare treatments for ectopic pregnancies has found no significant differences in subsequent fertility between medical treatment and conservative surgery on one hand, and conservative or radical …

Medicine & Health / Obstetrics & gynaecology
1 hour ago |
not rated yet |
0