# Mechanism of extracellular electron transfer in Gram-negative bacteria > **NIH NIH R01** · CORNELL UNIVERSITY · 2024 · $329,615 ## Abstract Toxic contaminants, such as heavy metals and organic compounds, pose serious health threats to sur- rounding communities. Bioremediation, which uses living organisms such as bacteria to degrade, detoxify, or remove pollutants, has emerged as an environmentally sustainable approach to cleaning up polluted sites. The Gram-negative bacterium Shewanella is capable of reducing metals like uranium and chromium to less-toxic forms as well as of degrading organic compounds through redox reaction as part of their anaerobic respiration. Leveraging the anaerobic respiration mechanism in Shewanella can thus revolutionize bioremediation and wastewater treatment technologies. The biological foundation of this anaerobic respiration is the extracellular electron transfer (EET) process, in which the bacterium exchanges electrons with extracellular electron accep- tors or donors by employing a cascade of proteins residing at different cellular compartments, in which CymA, an inner-membrane-anchored protein, acts as a central hub of EET pathways for relaying electrons across the inner-membrane, either toward outside the cell or into the cell. Little is known, however, on how the involved proteins, especially those at different cellular compartments, coordinate spatially and temporally in the cell to ensure efficient electron transfer. The long-term goal here is to understand how electroactive bacteria carry out EET to provide knowledge to better utilize or engineer such bacteria for bioremediation of contaminated sites. The objective here is to define how CymA coordinates spatially and temporally with its redox partners to mediate efficient EET across the cell envelope in live Shewanella oneidensis cells. Preliminary studies reveal that CymA changes its spatial distribution in the cell from a dispersed pattern into a punctate pattern when actively engaged in EET, which leads to our hypothesis that CymA and its redox partners dynamically cluster and colocalize spa- tiotemporally in the cell to ensure efficient electron transfer across the cell envelope. The research will test this hypothesis and use quantitative single-molecule/single-cell imaging approaches, together with specific protein tagging, genetic manipulations, single-cell (photo)electrochemical manipulation/measurements, and bulk bio- chemical assays. There are two aims: 1) Define the spatial pattern and temporal dynamics of CymA in the cell in relation to cell's EET activity. 2) Define the spatiotemporal pattern of periplasmic EET partners and their colo- calization with CymA in the cell. The research is significant because it will provide insights into the mechanism of EET across the cell envelope of Gram-negative bacteria and the molecular basis of anaerobic respiration in electroactive bacteria, and it will provide knowledge to potentially engineer S. oneidensis and other electroactive bacteria for bioremediation applications. The research is innovative because of the novel mechanism of spatio- tempor... ## Key facts - **NIH application ID:** 10933727 - **Project number:** 1R01GM154669-01 - **Recipient organization:** CORNELL UNIVERSITY - **Principal Investigator:** Peng Chen - **Activity code:** R01 (R01, R21, SBIR, etc.) - **Funding institute:** NIH - **Fiscal year:** 2024 - **Award amount:** $329,615 - **Award type:** 1 - **Project period:** 2024-09-01 → 2028-06-30 ## Primary source NIH RePORTER: https://reporter.nih.gov/project-details/10933727 ## Citation > US National Institutes of Health, RePORTER application 10933727, Mechanism of extracellular electron transfer in Gram-negative bacteria (1R01GM154669-01). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10933727. Licensed CC0. --- *[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*