Detection of bacteria 'eat' electrons

(There are countless bizarre diets that have been noticed by the imagination of the community over the years, but Harvard University scientists have identified a kind of diet that may be periodic. The most strange: eat sunlight and electricity.

Led by associate professor Peter Girguis and Arpita Bose, a doctoral researcher, a group of researchers found that a common bacterium called Rhodopseudomonas palustris can use natural electrical conductivity to drawing electrons from minerals deep in soil and sediment while still on the surface, allowing them to absorb the sunlight needed to produce energy. This research was presented in an article on February 26, 2014 in Nature Communications.

'When you think about electricity and living things, most of us are thinking of Mary Shelley's Frankenstein film for a long time, but we have known for a long time that all creatures actually use electronics - creation. " The center of the study is a process called extracellular electron transfer (EET) , which involves moving the electrons , " said Girguis. The electrons come in and out of the cells, which we can prove, is that these bacteria suck into electrons, these electrons go into their central metabolic processes, and we were able to describe some systems involved in that process'.

In nature, iron-based microorganisms provide the electrons they need to fuel the production of energy, but laboratory tests show that iron itself is not Important to this process. By attaching an electrode to a microbial laboratory group, the researchers observed that the bacteria could draw electrons from a non-iron source, suggesting that they could also use the Other electron-rich minerals - such as other metals and sulfur compounds - in nature.

'It is a factor of change , ' Girguis said. 'We have known for a long time that the aerobic and anaerobic world interacts through the diffusion of chemicals into and out of those domains. Accordingly, we also believe that this diffusion process also regulates the speed of the biochemical cycles. But this study has shown that the ability to carry out extracellular electron transport is a diffusion around. This could change the way we think about interactions between the aerobic and anaerobic worlds, and can change the way we calculate the biochemical cycle speed '.

Using genetic tools, researchers were able to identify an important gene for bacteria's ability to take electrons. When this gene is turned off, the bacteria's ability to absorb electrons decreases by about a third.

'We are very interested to find out exactly what genes play a role in sucking electrons ,' Girguis said. 'Related genes are found throughout other bacteria in nature, and we are not sure. "This study provides some very provocative evidence that other bacteria also do this."

The foundation for this new study has been established more than two decades ago, when researchers first described a type of "eating" rust by pushing electrons to oxygen atoms. iron oxide molecules.

The researchers later used this bacterium to build a type of 'fuel cell' in which bacteria pushed electrons not to rust, but to an electrode that could recover this current.

If some bacteria can produce the energy they need by moving electrons outside their cells, Girguis and colleagues wonder if other bacteria do the same by sucking. electrons in or not?

'That question brings us back to iron,' he said. 'The central bacteria of this paper are the contrasting images of rust-eating bacteria . Instead of using iron oxide to breathe, they actually produce iron oxide from free iron. '

However, access to free iron is not an easy thing.

Bacteria rely on sunlight to help generate energy, but the iron they need is in the sediments below the ground. To approach iron while still on the surface. These bacteria have developed a strange strategy. Bacteria seem to attract electrons through naturally occurring conductive minerals. Also, when bacteria pull electrons out of iron, they create iron oxide crystals that precipitate iron oxide crystals in the soil around them. Over time, these crystals can become conductors and act as conductors, allowing bacteria to oxidize minerals that they cannot reach.

'That solves the paradox for the type of sunlight-dependent organism,' Girguis said. 'The single-celled microbes that grow in biofilms have come up with an approach and take electrons from soil minerals through electric current so they can still stay under sunlight'.

Although Girguis is still skeptical about the effectiveness of using microorganisms capable of implementing EET to produce energy through fuel cells, he said there are many other applications - such as industry. pharmaceutical industry in which microorganisms can be put to use.

"I think the biggest application opportunity here is to use microbes that can draw electrons to produce something beneficial and know that you can give them electrons to do that through an electrode '.