Progress in Bacterial Bioelectronics: Modular Sensors and Fundamental Mechanisms

Recent scientific publications highlight significant advances in the field of bacterial bioelectronics, detailing both a new, flexible sensor platform and a fundamental discovery about how bacteria transfer electrons.

Development of a Modular Bioelectrical Sensor System

Researchers from Rice University, Tufts University, and Baylor College of Medicine have developed a novel bioelectrical sensor system named the electroactive co-culture sensing system (e-COSENS). The study was published in the journal Nature Biotechnology.

System Design and Function

The system employs two types of bacteria working in tandem:

• A "sensor" bacterium, such as E. coli, is engineered to produce a signaling molecule called quinone only when a specific target substance, or analyte, is present.
• A "reporter" bacterium, Lactiplantibacillus plantarum, uses the released quinone to generate a measurable electrical current at an electrode, signaling the analyte's detection.

Testing and Applications

The research team tested four versions of the system designed to detect different analytes in various environments:

• Heavy metal ions in bayou water.
• Inflammation markers in artificial saliva.
• Antimicrobial peptides in human fecal-derived samples.
• An antibiotic in milk.

Electrical signals were detected within hours, with some responses occurring in as few as 20 minutes.

Collaborators at Tufts University developed a compact electronic disk to pair with commercially available digital multimeters for potential field use.

Researcher Statements and Support

• Corresponding author Caroline Ajo-Franklin stated that e-COSENS is the first system allowing bioelectronic sensors to be engineered in a modular manner.
• First author Siliang Li said the division of labor between two bacteria makes the system flexible and that simplified hardware lowers the barrier to using bioelectronic sensors outside the lab.

The work was supported by the Cancer Prevention and Research Institute of Texas and the Army Research Office. Two authors have filed provisional patents related to the design.

Study on Protein Mechanism for Bacterial Electron Transfer

Separately, researchers at Cornell University have identified a key mechanism by which electroactive bacteria transport electrons across their cell envelopes. The research was published on February 17 in the journal Nature Communications.

Key Discovery

The study revealed that CymA proteins in the inner membrane of the bacterium Shewanella oneidensis synchronize to form a biomolecular condensate. This formation, not previously observed in this context, is described as critical for facilitating electron transfer through the cell's non-electroconductive membranes.

Research Methodology and Findings

• Using photoelectrochemistry-fluorescence microscopy, researchers observed that during extracellular electron transfer, CymA proteins reorganize into a clustered arrangement within the inner membrane.
• They demonstrated that applying an electrochemical signal could manipulate this protein pattern and spur the electron transfer process.
• Lead author Youngchan Park, along with the research team, quantified the spatiotemporal dynamics of this protein reorganization at a single-cell level.

Research Context

• Shewanella oneidensis is a Gram-negative bacterium with an inner membrane, an outer membrane, and a periplasmic space between them. These layers are primarily composed of insulating materials.
• Principal investigator Peng Chen stated that electrons require a specific mechanism to traverse this non-conductive cell envelope.

The technique has potential applications in biotechnologies requiring efficient electron shuttling, such as microbial energy conversion.

The project was led by Peng Chen and originated from a collaboration with co-author Buz Barstow. The work was supported by the National Institutes of Health (NIH).