In an article recently released in Advanced Science, scientists at the Laboratory of Organic Electronics at Linköping University describe the experiments they have conducted to measure extracellular electron transfer. Extracellular electron transfer refers to the process in which bacteria in oxygen-free environments metabolize organic compounds (such as lactate) respire electric charges as a byproduct. Also known as extracellular respiration, you can think of extracellular electron transfers as the process of bacteria releasing electrons. The new Linköping University study focuses on the development of an organic electrochemical transistor that allows for enhanced observations of this process.
Extracellular electron transfer is an important process for many electrochemical systems such as water purification, biosensors, and fuel cells. These systems add bacteria to their environs as an eco-friendly strategy of converting chemical energy to electricity. One common bacterium that is often added is called Shewanella oneidensis, which is known to produce electrical current when administered arsenic, arabinose, or organic acids.
The new study looked at Shewanella oneidensis through an improved transistor, making it possible to look at the bacteria in smaller quantities. Principal research engineer Gábor Méhes explains, "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."
"This is a first step towards understanding extracellular electron transfer in bacteria occupying only a small area with the help of a transistor, and how the conversion takes place between the bacteria and the electrode," adds 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."
Méhes is a co-corresponding author with senior lecturer Eleni Stavrinidou. Both scientists hope that their work will spur others to invest in optimizing microbial electrochemical systems that generate energy. They say this research can inform on a wide range of subjects, from broadening understanding of gastrointestinal conditions to supporting human life on oxygen-less Mars.