MAR 30, 2018 05:13 PM PDT

Towards the Creation of Living Machines

WRITTEN BY: Carmen Leitch

A special bacterium can function as a kind of miniature natural power plant, researchers say. A species of microbes called Shewanella oneidensis have a unique metabolism in which they interact with rocks in a way that is comparable to how we breathe. Now, Moh El-Naggar, an associate professor of physics, biological sciences, and chemistry at USC Dornsife and a team from USC and Caltech have learned how these bacteria transfer electrons across their membrane with a kind of nanowire.

This work, reported in the Proceedings of the National Academy of Sciences, may help advance a new kind of technology that uses microbes to generate energy. Bacteria that feed on organic material or other stuff like rust can create electricity, as explained in the video. Another kind of microbe being developed at USC can feed on waste, oxidizing organic substances in wastewater to generate a bit of electricity in the process. 

"Microbes are highly evolved machines," El-Naggar said. "And what we have here is a class that is really good at converting energy and interacting with the abiotic world."

These organisms also provide a window into how and what life might survive in places that lack oxygen, like in outer space or deep in the ocean. 

They live by moving electrons out of the cell, said El-Naggar. "If one were to shut down the ability to transfer the electron out of their system, they would not be able to make energy. The bacteria would basically suffocate," he explained.

These bacterial cells also have protruding filaments, which were thought to be a microbial feature called pili. In 2013, researcher Sahand Pirbadian discovered that these filaments were actually an extension of the cell membrane, covered in proteins that aid in the transport of iron - cytochromes.   

While microscopy enabled the researchers to understand the composition of the nanowire, they wanted to know if electrons could migrate along the cytochromes inside. A high density of these cytochromes might enable the electrons to move onto external surfaces.

 Scientist Moh El-Naggar studies bacteria that construct membrane wires to 'breathe' rock. This three-dimensional construct depicts a wire composed of spherical vesicles containing electron-transporting proteins (red and green). / Credit: Sahand Pirbadian of USC Dornsife and Poorna Subramanian of Caltech

Utilizing a technique called electron cryotomography, or ECT, the investigators could see the distribution of proteins that transport electrons in the nanowires. "These are not simple tubes," El-Naggar said. "They turned out to be more like a chain of membrane pearls, strung together."

While some of the transport proteins were touching, many were too far apart for an electron to traverse. The research team suggested that the proteins can float around the membrane. That would generate enough collisions to get electrons to move from one cytochrome to another until, at the end of the nanowire, they jump onto a rock or metal surface.

There is more work that remains to confirms that hypothesis. "My lab is driven by the idea that we could develop new machines, where living cells are functioning as part of a hybrid biotic-abiotic system," said El-Naggar. "We are trying [to] build the foundations of a new generation of living electronics."

 

Sources: AAAS/Eurekalert! Via USC, PNAS

About the Author
  • Experienced research scientist and technical expert with authorships on 28 peer-reviewed publications, traveler to over 60 countries, published photographer and internationally-exhibited painter, volunteer trained in disaster-response, CPR and DV counseling.
You May Also Like
SEP 20, 2019
Drug Discovery & Development
SEP 20, 2019
Drug Combination May Combat Deadly Drug-Resistant Fungus
A drug combination of anti-fungal and anti-bacterial medications may be effective against the spread of a highly infectious and deadly fungus--Candida auri...
SEP 20, 2019
Health & Medicine
SEP 20, 2019
Rumors Disrupt Efforts To Control Ebola Outbreak
In the Democratic Republic of Congo (DRC), there is some doubt that Ebola is a real disease. Locals sometimes claim the illness was “brought in ...
SEP 20, 2019
Genetics & Genomics
SEP 20, 2019
A Sea Slug and Algae Rely on a Bacterial Weapons Factory
The inch-long sea slug Elysia rufescens eats algae for sustenance, but it gets an added benefit in the form of toxins within the algae....
SEP 20, 2019
Microbiology
SEP 20, 2019
Noninvasive New Test Can Diagnose Bowel Disease
This test doesn't require the preparation or anesthesia that a colonoscopy necessitates, and can detect damage that can't be seen....
SEP 20, 2019
Microbiology
SEP 20, 2019
Specific Gut Microbes Slow ALS Progression in a Mouse Model
We've come a long way in the five years since the ice bucket challenge drew attention to amyotrophic lateral sclerosis (ALS)....
SEP 20, 2019
Genetics & Genomics
SEP 20, 2019
A Pathogen That Has Evolved to Spread in Hospitals
Clostridium difficile is the primary cause of infections that are acquired in hospital settings; it causes diarrhea and intestinal inflammation....
Loading Comments...