Using tiny electrodes to measure electrical activity in bacteria

June 17, 2020

Scientists at Laboratory of Organic Electronics, Linköping University, have developed an organic electrochemical transistor that they can use to measure and study in fine detail a phenomenon known as extracellular electron transfer in which bacteria release electrons.

The study of bacteria and their significance for the natural world, and for human society and health, is a growing research field, as new bacteria are continuously being discovered. A human body contains more bacteria than human cells, and a millilitre of fresh water can hold as many as a million bacteria. Respiration in a normal human cell and in many bacteria takes place through biochemical reactions in which a compound, often glucose, reacts with oxygen to form carbon dioxide and water. During the process, energy is converted to a form that the cell can use. In oxygen-free environments, bacteria are found that metabolise organic compunds, like lactate, and instead of forming water, they release, or respire, electric charges, a by product of metabolism, into the environment. The process is known as extracellular electron transfer, or extracellular respiration.

The phenomenon is currently used in several electrochemical systems in applications such as water purification, biosensors and fuel cells. Adding bacteria is an eco-friendly way to convert chemical energy to electricity.

One such bacteria often used in research is Shewanella oneidensis, which previous research has shown to produce electrical current when fed with arsenic, arabinose (a type of sugar) or organic acids. A similar bacterium has recently been discovered in the human gastrointestinal system.

We do not, however, understand in detail what happens when bacteria release charges. In order to capture and measure the amount of charge released, electrodes are placed into the microbial systems. An individual bacterium gives a very weak signal, and thus until now, researchers have had to be satisfied with studying extracellular electron transfer in large systems with large numbers of bacteria.

In order to increase our understanding, scientists at the Laboratory of Organic Electronics at Linköping University have employed a combination of microelectronics, electrochemistry and microbiology. They have developed an organic electrochemical transistor in which they have been able to deposit Shewanella oneidensis on one of the microelectrodes, with a surface area of only a quarter of a square millimetre. The amplification of the signal that occurs in the transistor makes it possible for them to study in detail what happens when various substances are added to the system. They describe in an article in Advanced Science experiments in which they fed lactate to the bacteria.

"We have shown that we can detect very small differences in extracellular electron transfer, in other words the amount of charge released by the bacteria. Another plus is that we can achieve very short response times, and obtain a stable signal within ten minutes", says principal research engineer Gábor Méhes, who, together with senior lecturer Eleni Stavrinidou, is corresponding author for the article.

"This is a first step towards understanding extracellular electron transfer in bacteria occupying olny a small area with the help of a transistor, and how the conversion takes place between the bacteria and the electrode", says Gábor Méhes. "One future goal is to learn how bacteria interact with each other, and with other cells and chemical substances in the human gastrointestinal tract."

The research is being conducted within the framework of the Biocom Lab at the Laboratory of Organic Electronics, and is financed by Vinnova, the Swedish Research Council, the Swedish Foundation for Strategic Research, the Wallenberg Wood Science center and the European Research Council, ERC.

It is hoped that the research will lead to optimising microbial electrochemical systems that harvest energy, and increase our understanding of, for example, serious gastrointestinal conditions. Looking far inte the future, the idea has been raised among reserachers of using bacteria that respire iron compounds to support human life on the oxygen-free planet Mars.
Organic microbial electrochemical transistor monitoring extracellular electron transfer, Gábor Méhes, Arghyamalya Roy, Xenofon Strakosas, Magnus Berggren, Eleni Stavrinidou, and Daniel T. Simon, Advanced Science 2020, doi 10.1002/advs.202000641

Contact: Gábor Méhes,, +46 11 36 34 69

Linköping University

Related Bacteria Articles from Brightsurf:

Siblings can also differ from one another in bacteria
A research team from the University of Tübingen and the German Center for Infection Research (DZIF) is investigating how pathogens influence the immune response of their host with genetic variation.

How bacteria fertilize soya
Soya and clover have their very own fertiliser factories in their roots, where bacteria manufacture ammonium, which is crucial for plant growth.

Bacteria might help other bacteria to tolerate antibiotics better
A new paper by the Dynamical Systems Biology lab at UPF shows that the response by bacteria to antibiotics may depend on other species of bacteria they live with, in such a way that some bacteria may make others more tolerant to antibiotics.

Two-faced bacteria
The gut microbiome, which is a collection of numerous beneficial bacteria species, is key to our overall well-being and good health.

Microcensus in bacteria
Bacillus subtilis can determine proportions of different groups within a mixed population.

Right beneath the skin we all have the same bacteria
In the dermis skin layer, the same bacteria are found across age and gender.

Bacteria must be 'stressed out' to divide
Bacterial cell division is controlled by both enzymatic activity and mechanical forces, which work together to control its timing and location, a new study from EPFL finds.

How bees live with bacteria
More than 90 percent of all bee species are not organized in colonies, but fight their way through life alone.

The bacteria building your baby
Australian researchers have laid to rest a longstanding controversy: is the womb sterile?

Hopping bacteria
Scientists have long known that key models of bacterial movement in real-world conditions are flawed.

Read More: Bacteria News and Bacteria Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to