While bacteria that produce electricity have been found in exotic environments like mines and the bottoms of lakes, scientists have missed a source closer to home: the human gut.
Scientists discovered that a common diarrhea-causing bacterium, Listeria monocytogenes, produces electricity using an entirely different technique from known electrogenic bacteria, and that hundreds of other bacterial species use this same process.
Many of these sparking bacteria are part of the human gut microbiome, and many, like the bug that causes the food-borne illness listeriosis, which can also cause miscarriages, are pathogenic. The bacteria that cause gangrene (Clostridium perfringens) and hospital-acquired infections (Enterococcus faecalis) and some disease-causing streptococcus bacteria also produce electricity. Other electrogenic bacteria, like Lactobacilli, are important in fermenting yogurt, and many are probiotics.
"The fact that so many bugs that interact with humans, either as pathogens or in probiotics or in our microbiota or involved in fermentation of human products, are electrogenic -- that had been missed before," said the senior author. "It could tell us a lot about how these bacteria infect us or help us have a healthy gut."
The discovery will be good news for those currently trying to create living batteries from microbes. Such "green" bioenergetic technologies could, for example, generate electricity from bacteria in waste treatment plants. The research is published in the journal Nature.
Bacteria generate electricity for the same reason we breathe oxygen: to remove electrons produced during metabolism and support energy production. Whereas animals and plants transfer their electrons to oxygen inside the mitochondria of every cell, bacteria in environments with no oxygen --- including our gut, but also alcohol and cheese fermentation vats and acidic mines --- have to find another electron acceptor. In geologic environments, that has often been a mineral --- iron or manganese, for example --- outside the cell. In some sense, these bacteria "breathe" iron or manganese.
Transferring electrons out of the cell to a mineral requires a cascade of special chemical reactions, the so-called extracellular electron transfer chain, which carries the electrons as a tiny electrical current. Some scientists have tapped that chain to make a battery: stick an electrode in a flask of these bacteria and you can generate electricity.
The newly discovered extracellular electron transfer system is actually simpler than the already known transfer chain, and seems to be used by bacteria only when necessary, perhaps when oxygen levels are low. So far, this simpler electron transfer chain has been found in bacteria with a single cell wall --- microbes classified as gram-positive bacteria --- that live in an environment with lots of flavin, which are derivatives of vitamin B2.
"It seems that the cell structure of these bacteria and the vitamin-rich ecological niche that they occupy makes it significantly easier and more cost effective to transfer electrons out of the cell," said first author. "Thus, we think that the conventionally studied mineral-respiring bacteria are using extracellular electron transfer because it is crucial for survival, whereas these newly identified bacteria are using it because it is 'easy.'"
The authors used an electrode to measure the electric current that streams from the bacteria --- up to 500 microamps --- confirming that it is indeed electrogenic. In fact, they make about as much electricity --- some 100,000 electrons per second per cell --- as known electrogenic bacteria.
The authors are particularly intrigued by the presence of this system in Lactobacillus, bacteria crucial to the production of cheese, yogurt and sauerkraut. Perhaps, they suggest, electron transport plays a role in the taste of cheese and sauerkraut.
"This is a whole big part of the physiology of bacteria that people didn't realize existed, and that could be potentially manipulated," the lead author said.
The authors have many more questions about how and why these bacteria developed such a unique system. Simplicity --- it's easier to transfer electrons through one cell wall rather than through two --- and opportunity --- taking advantage of ubiquitous flavin molecules to get rid of electrons - appear to have enabled these bacteria to find a way to survive in both oxygen-rich and oxygen-poor environments.
http://news.berkeley.edu/2018/09/12/gut-bacterias-shocking-secret-they-produce-electricity/
https://www.nature.com/articles/s41586-018-0498-z
Latest News
Wiring of the human neocortex
By newseditor
Posted 24 Apr
Abusive drugs hijack natura…
By newseditor
Posted 23 Apr
Mechanism of action of the…
By newseditor
Posted 23 Apr
Role of fat in rare neurolo…
By newseditor
Posted 23 Apr
How protein synthesis in de…
By newseditor
Posted 22 Apr
Other Top Stories
Laboratory technique recapitulates all stages of egg cell development
Read more
Babies' spatial reasoning predicts later math skills
Read more
Embryos with "heteroplasmy," or the presence of both maternal and p…
Read more
Immune cell involvement in brain development revealed!
Read more
Blood cell types emerge through internal struggles
Read more
Protocols
A programmable targeted pro…
By newseditor
Posted 23 Apr
MemPrep, a new technology f…
By newseditor
Posted 08 Apr
A tangible method to assess…
By newseditor
Posted 08 Apr
Stem cell-derived vessels-o…
By newseditor
Posted 06 Apr
Single-cell biclustering fo…
By newseditor
Posted 01 Apr
Publications
Harnessing gastrointestinal…
By newseditor
Posted 24 Apr
Sex-specific modulation of…
By newseditor
Posted 24 Apr
Exploiting pancreatic cance…
By newseditor
Posted 23 Apr
Structure of antiviral drug…
By newseditor
Posted 23 Apr
Type-I-interferon-responsiv…
By newseditor
Posted 23 Apr
Presentations
Hydrogels in Drug Delivery
By newseditor
Posted 12 Apr
Lipids
By newseditor
Posted 31 Dec
Cell biology of carbohydrat…
By newseditor
Posted 29 Nov
RNA interference (RNAi)
By newseditor
Posted 23 Oct
RNA structure and functions
By newseditor
Posted 19 Oct
Posters
A chemical biology/modular…
By newseditor
Posted 22 Aug
Single-molecule covalent ma…
By newseditor
Posted 04 Jul
ASCO-2020-HEALTH SERVICES R…
By newseditor
Posted 23 Mar
ASCO-2020-HEAD AND NECK CANCER
By newseditor
Posted 23 Mar
ASCO-2020-GENITOURINARY CAN…
By newseditor
Posted 23 Mar