New Extremophiles: living by expelling electrons to rocks (Introduction)

by David Turell , Saturday, March 31, 2018, 01:51 (2209 days ago) @ David Turell

They do it through 'nanowires' made of extended cell membrane proteins:

https://phys.org/news/2018-03-electron-carrying-proteins-secret-electric-bacteria.html

"Scientist Moh El-Naggar and his team think it's possible. They work with the Shewanella oneidensis species of bacteria, one of a group of microbes that essentially "breathe" rocks.

"As part of their metabolism, the bacteria have developed a way to transfer electrons from the interior of the cell across their outer membrane to a receiving surface in the outside world.

"The process is akin to the way humans use oxygen to breathe. The body takes electrons from food and, ultimately, transfers those electrons to oxygen.

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"'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."

"Another advantage to using "electric bacteria" is already being explored at USC—wastewater treatment. Microbes feed on the waste, oxidizing the organic substances and producing a small amount of electricity.

***

"Depositing electrons outside the cell is how they survive, said El-Naggar, who holds the Robert D. Beyer ('81) Early Career Chair in Natural Sciences. "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."

"Under the microscope, scientists can see what appear to be filaments projecting from these cells. For years, the prevailing hypothesis was that these were a form of tiny hairs called pili, similar to those found on other types of bacteria.

"But in 2013, a research scientist in El-Naggar's laboratory, Sahand Pirbadian, discovered that these projections, referred to as "nanowires," were actually extensions of the cell membrane covered in cytochromes—proteins containing iron that facilitate electron transport.

"These nanowires allow the bacteria to connect with surfaces much further away than one would expect.

"Through light microscopy imaging, the team had an idea of the nanowires' basic composition. But they were curious as to whether the cytochromes were close enough together to transport electrons along the wire. If the density were high enough, they thought a bridge could form along the membrane that would allow an electron to cross onto external surfaces.

***

"Subramanian and Pirbadian were able to capture life-like images of the bacteria and their nanowires. What they found was intriguing.

"'These are not simple tubes," El-Naggar said. "They turned out to be more like a chain of membrane pearls, strung together."

"With the images produced by ECT, the team was the first to see how electron transport proteins were distributed in the membrane to form the nanowires. While some were touching each other, many were further apart—up to 30 nanometers—a range too far for an electron to jump.

"With this new information, the team proposed that the proteins float within the membrane. This creates just enough collisions to allow electrons to exchange from one to the next until they reach the end of the nanowire and transfer to the rock or metal surface."

Comment: Life undoubtedly stated with bacteria-like organisms, which were given designed genetic instructions to make life tenacious and to survive any challenges. The proof of that tenacity is they are still here as the largest, most diverse biomass on Earth. I believe God started life, and meant that it would always survive. What has evolved beyond bacteria is undoubtedly not as tough, although representing a different kind of complexity.