Nationalgeographic.co.id—Deep beneath the seabed, found bacteria little one that “blows” electricity through a long, small snorkel. Now, scientists have figured out how to turn your breath on and off electricity these microbes.
Bacteria This weirdness relies on two proteins, which are united in one so -called hair -like structure pilus (Latin for hair; plural: Pili). Researchers report in a new study, published Wednesday (September 1) in the journal Nature. Many of these pili are located just below the membrane bacteria and helps propel the snorkel out of the cell and into the surrounding environment, allowing microbes to breathe.
“Invention this not only reveals something unexpected about biology bacteria but can also pave the way for technology new, from powerful microbial-powered batteries to new medical treatments for infections bacteria,” said senior Nikhil Malvankar, assistant professor of molecular biophysics and biochemistry at Yale University’s Institute of Microbial Sciences. Live Science.
Bacteria It belongs to the genus Geobacter and can be found all over the world, growing deep underground where there is absolutely no oxygen. Humans depend on oxygen to convert food into usable energy and to absorb the electrons left over from this metabolic process. If the remaining electrons accumulate, they will quickly become toxic to the body, says Malvankar.
Just like humans, Geobacter microbes produce waste electrons during metabolism, but they don’t have access to oxygen like we do. So, to get rid of the excess electrons, bacteria coats itself in thin, conductive filaments, called nanowires, which can move electrons out of the microbe and into the bacteria or other minerals in the environment, such as iron oxide.
These thin nanowires are 100,000 times smaller than the width of a human hair and can transport electrons over great distances, hundreds to thousands of times the length of the original microbial body.
Derek Lovley Kelly Nevin & Ben Barnhart, University of Massachusetts
Geobacter, an iron-breathing microbe. Scientists have finally discovered the switch button in bacteria that emits an electric breath, and is being developed further.
“Humans cannot breathe oxygen 100 meters away from them,” said Malvankar. “And somehow these bacteria use these nanowires like snorkels that are 100 times the size, so they can still breathe over such great distances.” This impressive feat generates an electric current, as electrons continue to flow through the long nanowire.
But although scientists discovered these nanowires in the early 2000s, Malvankar and his colleagues have only recently discovered what the snorkel is actually made of. Initially, scientists assumed that nanowires were second. This idea seems to be supported by the fact that, if you remove the gene required for construction second from the Geobacter bacteria, nanowires no longer appear on their surfaces, Malvankar said.
But there is a problem: Protein second does not contain metals, such as iron, which conduct electricity. Malvankar and his team investigated this puzzle in a 2019 study, published in the journal Cell, in which they examined Geobacter bacteria using cryo-electron microscopy (cryo-EM), a technique that involves beaming electrons through a substance to take snapshots of its component molecules. .
“That’s when we realized that there were no pili on the surface of the bacteria at all,” Malvankar said. “It was a big surprise.”
Instead, the team found that the nanowires are made of proteins called cytochromes, which easily transfer electrons all the way to their ends and therefore make nanowires much better than pili. In a 2020 study, published in the journal Nature Chemical Biology, the team reports that these cytochrome-based nanowires come in a variety of “flavors”, which conduct electricity with different degrees of efficiency.
But even after the team revealed the chemical makeup of the nanowires, pili proteins still appeared in the biochemical assessment of the bacteria Geobacter. If pili do not conduct electricity, “the real big question is, what do these pili actually do? Where are they?” Malvankar said.
In their latest Nature study, the team took a closer look at the structure of these pili by first deleting the gene for the nanowire and developed in the laboratory of Geobacter sulfurreducens. Pili would normally be blocked by nanowires, so without that structure getting in the way, hair-like projections grow from the cell surface. This gave the team the opportunity to examine the pili by cryo-EM, which revealed two different proteins—PilA-N and PilA-C—in each hair.
Derek Lovley/Science Photo Library
Geobacter Metallireducens Bacterium. Gram negative metal reducing proteobacterium. It oxidizes several short chain fatty acids, alcohols, and monoaromatic compounds with Fe(III) as the single electron acceptor.
The team also ran tests to see how well pili conduct electricity, and found that “they move electrons 20,000 times slower than OmcZ,” the most conductive cytochrome protein and form Geobacter nanowires, Malvankar said; “they’re not really made to move electrons.”
The pili seem to have a different function. In other bacterial species, some pili sit under the cell membrane and move like tiny pistons; this movement allows them to push proteins through the membrane, and in and out of the cell.
For example, the bacterium Vibrio cholerae, which causes the diarrheal disease cholera, uses the pili to excrete the cholera toxin, according to a 2010 report in the journal Nature Structural & Molecular Biology. In a series of experiments, the team determined that the pili in Geobacter fulfill a similar role, namely helping to propel nanowires through microbial membranes.
“We found that the cytochromes were trapped inside the bacteria when the piston protein was not present,” said Malvankar. “And when we restore the gene, the cytochromes can come out of the bacteria.” This, likely, is the bacteria’s on-off switch, the team concludes.
Going forward, the researchers plan to investigate how many other types of bacteria build nanowires and use them to breathe electricity. They are also interested in exploring practical applications for such research.
Researchers have been using Geobacter colonies to power tiny electronics for more than a decade, but until now, these batteries had only been able to generate small amounts of power.
In previous research, Malvankar and his team found that colonies can be made more conductive under the influence of an electric field, which could help increase the power of these devices; Now, new research could give scientists another level of control, by allowing them to turn electricity on or off.
The research could also be applied in medicine and, in particular, in treatments for bacterial infections, Malvankar said. For example, Salmonella beats the good bacteria in the gut because it can switch from fermentation, which produces energy slowly without requiring oxygen, to respiration, which produces energy quickly and usually requires oxygen.
In a low-oxygen gut environment, Salmonella uses a compound called tetrathionate instead of oxygen, so it can defeat the good bacteria in the body.
However, what if the helpful bacteria could rise? In theory, if you supplement bacteria with nanowires and insert them into your gut, as a kind of probiotic treatment, they could potentially defeat dangerous pathogens like Salmonella, Malvankar said. Malvankar and his colleagues are studying this potential treatment, but the work is still in its early stages.