Developing 'green' electronics: Team finds microbe from the Potomac yields better electronic material

January 17, 2017
An artist's rendition of Geobacter expressing electrically conductive nanowires. Microbiologists at UMass Amherst have discovered a new type of natural wire produced by bacteria that could greatly accelerate the development of sustainable "green" conducting materials for the electronics industry. Credit: UMass Amherst

Microbiologists at the University of Massachusetts Amherst report that they have discovered a new type of natural wire produced by bacteria that could greatly accelerate the researchers' goal of developing sustainable "green" conducting materials for the electronics industry. The study by Derek Lovley and colleagues appears this week in mBio, the American Society of Microbiology's premier journal.

The researchers studied microbial nanowires, protein filaments that bacteria use naturally to make electrical connections with other microbes or minerals.

As Lovley explains, "Microbial nanowires are a revolutionary electronic material with substantial advantages over man-made materials. Chemically synthesizing nanowires in the lab requires toxic chemicals, high temperatures and/or expensive metals. The energy requirements are enormous. By contrast, natural microbial nanowires can be mass-produced at room temperature from inexpensive renewable feedstocks in bioreactors with much lower energy inputs. And the final product is free of toxic components."

"Microbial nanowires therefore offer an unprecedented potential for developing novel materials, electronic devices and sensors for diverse applications with a new environmentally friendly technology," he adds. "This is an important advance in microbial nanowire technology. The approach we outline in this paper demonstrates a rapid method for prospecting in nature to find better electronic materials."

Until now Lovely's lab has been working with the nanowires of just one bacterium, Geobacter sulfurreducens. "Our early studies focused on the one Geobacter because we were just trying to understand why a microbe would make tiny wires," Lovley says. "Now we are most interested in the nanowires as an electronic material and would like to better understand the full scope of what nature may have to offer for these practical applications."

When his lab began looking at the protein filaments of other Geobacter species, they were surprised to find a wide range in conductivities. For example, one species recovered from uranium-contaminated soil produced poorly conductive filaments. However, another species, Geobacter metallireducens - coincidentally the first Geobacter ever isolated - produced nanowires 5,000 times more conductive than the G. sulfurreducens wires. Lovley recalls, " I isolated metallireducens from mud in the Potomac River 30 years ago, and every couple of years it gives us a new surprise."

In their new study supported by the U.S. Office of Naval Research, they did not study the G. metallireducens strain directly. Instead, they took the gene for the protein that assembles into microbial nanowires from it and inserted this into G. sulfurreducens. The result is a genetically modified G. sulfurreducens that expresses the G. metallireducens protein, making nanowires much more conductive than G. sulfurreducens would naturally produce.

Further, Lovley says, "We have found that G. sulfurreducens will express filament genes from many different types of bacteria. This makes it simple to produce a diversity of filaments in the same microorganism and to study their properties under similar conditions."

"With this approach, we are prospecting through the to see what is out there in terms of useful conductive materials," he adds. "There is a vast reservoir of filament genes in the microbial world and now we can study the filaments produced from those genes even if the gene comes from a microbe that has never been cultured."

The researchers attribute G. metallireducens nanowires' extraordinarily high conductivity to its greater abundance of aromatic amino acids. Closely packed aromatic rings appear to be a key component of microbial nanowire conductivity, and more aromatic rings probably means better connections for electron transfer along the .

The high conductivity of the G. metallireducens nanowires suggests that they may be an attractive material for the construction of conductive materials, electronic devices and sensors for medical or environmental applications. The authors say discovering more about the mechanisms of nanowire conductivity "provides important insight into how we might make even better wires with genes that we design ourselves."

Explore further: 'Green' electronic materials produced with synthetic biology

More information: Expressing the Geobacter metallireducens PilA in Geobacter sulfurreducens Yields Pili with Exceptional Conductivity, DOI: 10.1128/mBio.02203-16 , http://mbio.asm.org/content/8/1/e02203-16.abstract

Related Stories

Down to the wire: Researchers and new bacteria

August 16, 2016

Scientists sponsored by the Office of Naval Research (ONR) have genetically modified a common soil bacteria to create electrical wires that not only conduct electricity, but are thousands of times thinner than a human hair.

Bacteria use hydrogen, carbon dioxide to produce electricity

May 20, 2013

Researchers have engineered a strain of electricity-producing bacteria that can grow using hydrogen gas as its sole electron donor and carbon dioxide as its sole source of carbon. Researchers at the University of Massachusetts, ...

Bacteria hairs make excellent electrical wires

June 7, 2016

Although proteins are usually electrically insulating, hair-like nanoscale filaments (called pili) on the surface of Geobacter bacteria exhibit metallic-like conductivity. To understand why pili are conductive, scientists ...

Recommended for you

Atomic blasting creates new devices to measure nanoparticles

December 14, 2017

Like sandblasting at the nanometer scale, focused beams of ions ablate hard materials to form intricate three-dimensional patterns. The beams can create tiny features in the lateral dimensions—length and width, but to create ...

Engineers create plants that glow

December 13, 2017

Imagine that instead of switching on a lamp when it gets dark, you could read by the light of a glowing plant on your desk.

Faster, more accurate cancer detection using nanoparticles

December 12, 2017

Using light-emitting nanoparticles, Rutgers University-New Brunswick scientists have invented a highly effective method to detect tiny tumors and track their spread, potentially leading to earlier cancer detection and more ...

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

eachus
not rated yet Jan 17, 2017
It is nice to hear of something good coming out of Washington, DC. ;-)
FredJose
1 / 5 (1) Jan 19, 2017
One should just remember that though these filaments are found in "nature", it was not "nature" that designed them. "Nature" is not a living, functional and intelligent agent. "Nature" is an abstract concept that conveys the idea of all of what occurs in a natural state not created by human kind.
So in fact, since "nature" did not design anything, that only leaves the person who designed all of creation - and it must have been an intelligent agent because it was all designed and constructed with a purpose in mind as can be seen by the almost miraculous amounts of specification that abounds in biological system alone, never mind the rest.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.