Extracellular polymeric substances are transient media for microbial extracellular electron transfer
By Yong Xiao, En-Hua Zhang, Jingdong Zhang, Youfen Dai, Zhao-hui Yang, H. Christensen, J. Ulstrup, F. Zhao. Science Advances, 2017
666 citations recorded by the source corpus.
Extracellular polymeric substances play important roles in microbial extracellular electron transfer processes. Microorganisms exploit extracellular electron transfer (EET) in growth and information exchange with external environments or with other cells. Every microbial cell is surrounded by extracellular polymeric substances (EPS). Understanding the roles of three-dimensional (3D) EPS in EET is essential in microbiology and microbial exploitation for mineral bio-respiration, pollutant conversion, and bioenergy production. We have addressed these challenges by comparing pure and EPS-depleted samples of three representative electrochemically active strains viz Gram-negative Shewanella oneidensis MR-1, Gram-positive Bacillus sp. WS-XY1, and yeast Pichia stipites using technology from electrochemistry, spectroscopy, atomic force microscopy, and microbiology. Voltammetry discloses redox signals from cytochromes and flavins in intact MR-1 cells, whereas stronger signals from cytochromes and additional signals from both flavins and cytochromes are found after EPS depletion. Flow cytometry and fluorescence microscopy substantiated by N-acetylglucosamine and electron transport system activity data showed less than 1.5% cell damage after EPS extraction. The electrochemical differences between normal and EPS-depleted cells therefore originate from electrochemical species in cell walls and EPS. The 35 ± 15–nm MR-1 EPS layer is also electrochemically active itself, with cytochrome electron transfer rate constants of 0.026 and 0.056 s−1 for intact MR-1 and EPS-depleted cells, respectively. This surprisingly small rate difference suggests that molecular redox species at the core of EPS assist EET. The combination of all the data with electron transfer analysis suggests that electron “hopping” is the most likely molecular mechanism for electrochemical electron transfer through EPS.
Subfields: Electrical and Electronic Engineering, Environmental Engineering, Water Science and Technology
View Paper: https://www.semanticscholar.org/paper/054c450dece2b89f2760a249f3bd27e6ac34d620
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Citations in the corpus
- Electrochemical roles of extracellular polymeric substances in biofilms (2017, background): “(A) Previous studies with proposed direct and indirect microbial EET mechanisms [6] .”