전기 만들어내는 장내 미생물의 비밀 The Bacteria in Your Gut Produce Electricity

The Bacteria in Your Gut Produce Electricity

By Yasemin Saplakoglu, Staff Writer | September 13, 2018

There may not be butterflies in your stomach, but there are certainly sparks in your gut.

Some types of bacteria that are either commonly consumed or already found in our guts can create electricity, according to a new study published Wednesday (Sept. 12) in the Journal Nature.

Some bacteria, like Listeria monocytogenes, can generate electricity. These bacteria transport electrons through the cell wall into the surrounding environments, with help from flavin molecules (shown in yellow).

Credit: Amy Cao graphic. Copyright UC Berkeley.

전기 만들어내는 장내 미생물의 비밀 설사 일으키는 미생물 리스테리아균(Listeria monocytogenes) 전기 생산 세균, 인체 내에서 발견된 건 처음 UC버클리 대니얼 포트노이 교수팀   대니얼 포트노이 미국 버클리 캘리포니아대(UC버클리) 분자세포생물학부 교수팀은 설사를 일으키는 미생물인 리스테리아균(Listeria monocytogenes)이 전기를 생산한다는 사실을 발견해 국제학술지 ‘네이처’ 9월 12일자에 발표했다. 그동안 전기를 생산하는 세균이 존재한다는 사실은 알려져 있었지만, 전기 생산 세균이 인체 내에서 발견된 건 처음이다. 리스테리아균은 기존에 전기를 생산하는 것으로 알려진 쉬와넬라 오나이덴시스(Shewanella oneidensis) 같은 세균보다 간단한 방식으로 전자를 운반해 전기를 생산하는 것으로 확인됐다. 리스테리아균은 쉬와넬라균과 달리 세포벽 구조가 간단한 그람양성균이기 때문에 전자가 움직이기에 더 용이하다.  연구팀은 이와 함께 장내에 서식하는 세균 수백 종이 전기를 생산한다는 사실을 추가로 확인했다. 여기에는 병원성 세균인 가스괴저균, 포도상구균, 엔테로코쿠스 패칼리스외에도 유익한 유산균인 락토바실러스 등이 포함됐다. 이들은 모두 그람양성균이다.   포트노이 교수는 “우리 가까이에 있는 박테리아들을 오히려 놓치고 있었던 셈”이라며 “앞으로 세균을 이용해 친환경 전기를 생산하는 데 이 연구가 중요한 역할을 할 것”이라고 말했다. 신용수 기자 credits@donga.com 동아사이언스

edited by kcontents

Electricity-generating, or "electrogenic," bacteria aren't something new — they can be found in places far away from us, like at the bottom of lakes, said senior author Daniel Portnoy, a microbiologist at the University of California, Berkeley. [5 Ways Gut Bacteria Affect Your Health]

But until now, scientists had no idea that bacteria found in decaying plants or in mammals, especially farm animals, could also generate electricity — and in a much simpler manner, Portnoy said.

In the lab, Portnoy and his team first grew a batch of Listeria monocytogenes, a species of bacteria, that we often eat that sometimes causes an infection called listeriosis. This type of food poisoning typically is most dangerous for those with weakened immune systems, pregnant women (it can cause miscarriages), newborns and elderly people, according to the Centers for Disease Control and Prevention.

By placing the bacteria in an electrochemical chamber and capturing the generated electrons with a wire, or electrode, the team found that these foodborne bacteria created an electrical current.

Gut bacteria's shocking secret: They produce electricity/BioThix

edited by kcontents

Why the shock?

There are several reasons why some bacteria generate electricity, such as to remove electrons produced by metabolism, according to a statement. But the main purpose is to create energy, Portnoy said.

But Listeria monocytogenes has "other ways of generating energy too," such as through using oxygen, said lead author Sam Light, a postdoctoral researcher at the University of California, Berkeley. This electricity-generating process is "probably a back-up system that they use under certain conditions." For example, they may deploy it in low-oxygen conditions of the gut.

The researchers screened mutated bacteria — those with missing or altered genes — to identify which genes were necessary for the bacteria to produce electricity. Those genes in turn code for certain proteins that are key to producing electricity.

They found that the system these bacteria used — a cascade of proteins that carry the electrons out of the bacteria — was much simpler than systems other electrogenic bacteria (such as those living at the bottom of a lake) use.

Most other previous systems were found in gram-negative bacteria, or those with a cell wall composed of two layers that separates the inside from the environment. These recently analyzed bacteria are gram-positive, which means their cell walls have only one layer. "That means there's one less hurdle," for the electrons to reach the outside, Light told Live Science.

But once the electrons do reach the outside, it's unclear where they go. Electrogenic bacteria elsewhere typically transfer the electrons to minerals like iron or manganese in their environment. In the research team's experiments, the electrons flowed into the electrode. In the gut, a number of different molecules, such as iron, could potentially bind to and accept electrons, Light said.

They also found that the bacteria needed flavin proteins to survive. Flavin, a variant of vitamin B2, densely populates the gut. The researchers later found that the bacteria not only needed flavin to survive, but that extra, free-floating flavin in the surrounding environment could enhance the bacteria's electrical activity.

Energy-generating bacteria

Once they knew which genes were responsible for electricity generation, the team further identified hundreds of other microbes that generate electricity using this simpler process — a number of them commonly reside in the gut, while others are important in fermenting yogurt or serving as probiotics.

In a commentary published in Nature the same day, University of Illinois microbiologists Laty Cahoon and Nancy Freitag, who were not involved in the study, wrote, "It is a shock to the system to consider that microbes might be living highly charged lives in our gut." Knowledge of this new electricity-generating pathway "might create opportunities for the design of bacteria-based energy-generating technologies," the researchers wrote.

There are already efforts to create microbial fuel cells, or batteries that use bacteria to generate electricity using organic matter, like in waste-treatment plants. Because this new process is simpler, there's a chance it can improve such technology, but it's too soon to say for sure, Light said.

He personally is more interested in understanding exactly what is going on in the gut — which molecules receive electrons from the bacteria and how this process affects bacterial survival.

Originally published on Live Science.

https://www.livescience.com/63569-gut-bacteria-produces-electricity.html

kcontents