Cornell Researchers Uncover Key Bacterial Electron Transport Mechanism
Cornell University researchers have identified a key mechanism by which electroactive bacteria transport electrons across their multi-layered cell envelopes. This process is crucial for bacterial interaction with external environments and involves a synchronized effort by specific proteins.
Discovery of CymA Protein Condensates
The research, published on February 17 in Nature Communications, revealed that CymA proteins in the inner membrane of electroactive bacteria synchronize and form a biomolecular condensate. This formation had not been previously observed in electroactive bacteria and is considered critical for facilitating electron transfer through otherwise non-electroconductive membranes.
Researchers demonstrated that applying an electrochemical signal to the bacteria could manipulate the spatial pattern of these proteins. This manipulation successfully spurred the extracellular electron transfer process.
Research Context and Implications
This technique has potential applications in biotechnologies such as microbial energy conversion, where efficient electron shuttling to other cells or electrodes is required.
The project was led by Peng Chen, the Peter J.W. Debye Professor of Chemistry, and originated from a collaboration with co-author Buz Barstow, assistant professor of biological and environmental engineering. The study focused on Shewanella oneidensis, a well-studied Gram-negative bacterium known for electron transport. S. oneidensis possesses an inner membrane, an outer membrane, and a periplasmic space. These layers, primarily composed of insulating fatty lipids, are not electroconductive.
Chen stated that electrons do not simply pass through water but require a mechanism to traverse the cell envelope, which includes both membranes and the periplasm. Using photoelectrochemistry-fluorescence microscopy, the team observed that during extracellular electron transfer, CymA proteins reorganize within a confined region in the inner membrane. This reorganization subsequently prompts their electron-transfer partners in the periplasm to adopt a similar clustered arrangement.
The ability to induce CymA condensate formation using electrochemical signals allowed researchers to quantify the spatiotemporal dynamics of protein reorganization at a single-cell level. This finding indicates that an electrical signal can cause a protein's spatial pattern to change from homogeneous to condensed, which represents a novel observation in the context of electron transfer.
The Research Team
The lead author of the study was former postdoctoral researcher Youngchan Park, now an assistant professor at Indiana University. Additional co-authors included doctoral student Tianlei Yan, Zhiheng Zhao, former postdoctoral researchers Bing Fu and Muwen Yang, and Farshid Salimijazi. The work was supported by the National Institutes of Health (NIH).