“Schematic diagrams illustrate multichannel bioelectronic sensing systems. a: Schematic of multichannel bioelectronic system, using CymA and Flavin pathways as channels to detect two analytes, processing signals and generating binary outputs. b: Redox potentials of the CymA and Flavin channels, at 0.077 V and –0.220 V vs. Ag/AgCl, respectively.”
MICROBIAL SENSORS
https://nature.com/articles/s41467-025-62256-1
https://scientificamerican.com/metal-breathing-bacteria-synthesize-high-tech-material
https://phys.org/news/2025-07-bacteria-based-sensors-real-arsenite.html
Bacteria-based sensors deliver real-time detection of arsenite and cadmium in water
by Marcy de Luna, edited by Stephanie Baum, reviewed by Andrew Zinin / July 29, 2025
“Researchers at Rice University have engineered E. coli to act as living multiplexed sensors, allowing these genetically modified cells to detect and respond to multiple environmental toxins simultaneously by converting their biological responses into readable electrical signals. This innovation opens the door to real-time, remote monitoring of water systems, pipelines and industrial sites with potential future applications in biocomputing. A new study published in Nature Communications demonstrates an innovative method for the real-time, on-site detection of arsenite and cadmium at levels set by the Environmental Protection Agency. This research, led by Xu Zhang, Marimikel Charrier and Caroline Ajo-Franklin, addresses a significant inefficiency in current bioelectronic sensors, which typically require dedicated communication channels for each target compound. The research team’s multiplexing strategy greatly enhances information throughput by leveraging bacteria’s innate sensitivity and adaptability within a self-powered platform. “This system represents a major leap in bioelectronic sensing, encoding multiple signals into a single data stream and then decoding that data into multiple, clear yes-or-no readouts,” said Ajo-Franklin, the Ralph and Dorothy Looney Professor of Biosciences and corresponding author of the study.
Conventional bioelectronic sensors use engineered bacteria to generate electrical signals; however, each analyte usually demands its own dedicated engineered bacteria. The researchers were inspired by fiber-optic communication, where different light wavelengths carry distinct data streams over a single cable. They reasoned that electrical signals at varying redox potentials, or “energies,” could similarly multiplex information from a single sensor. “We needed to determine how to robustly separate signals of different energies regardless of the sample or toxin,” said Zhang, the study co-author and a biosciences postdoctoral researcher. The research team devised an electrochemical method that isolates these redox signatures and converts them into binary responses indicating the presence or absence of each toxin. Their work combined synthetic biology with electrochemical analysis, programming engineered E. coli strains to interact specifically with either arsenite or cadmium, resulting in distinct electrical responses. The system can simultaneously report on two toxins using a unified electrode setup by employing a sensor array that distinguishes these redox signatures.
The multiplexed sensors successfully detected arsenite and cadmium at EPA-standard thresholds in environmental tests. This capability is critical, especially given the potential for synergistic toxicity when both metals are present, a scenario that poses a greater risk than either contaminant alone. “This system allows us to detect combined hazards more efficiently and accurately,” said Charrier, the study co-author and a bioengineering senior research specialist. “Moreover, because the platform is modular, it could be scaled up to screen for more or different toxins simultaneously.” By integrating wireless technologies, the implications of the system extend beyond heavy metal monitoring. For example, the sensor could enable real-time, remote surveillance of water systems, pipelines and industrial sites. The underlying bioelectronic framework also points toward future applications in biocomputing, where engineered cells could not only sense and store environmental data but potentially process and transmit it via electronic interfaces.
This study lays a foundation for advanced biodigital integration. The research team’s work marks an early but notable step toward developing intelligent, self-powering biosensor networks. As the field of bioelectronics continues to evolve, the researchers say they envision multiplexed, wireless bacterial sensors becoming essential tools that can be deployed at scale for environmental monitoring, diagnostics and even biocomputational tasks, all powered by microorganisms. “A key advantage of our approach is its adaptability; we believe it’s only a matter of time before cells can encode, compute and relay complex environmental or biomedical information,” Ajo-Franklin said.”
More information: Xu Zhang et al, Multichannel bioelectronic sensing using engineered Escherichia coli, Nature Communications (2025). DOI: 10.1038/s41467-025-62256-1
“Geographic locales of microorganisms encoding elements of the MtrCAB system. The geographic location of isolation was unavailable for some sequences, and geographical sampling biases are apparent. Large red circles represent the South Pacific, North Atlantic, and Indian Ocean (Eastern Africa Coastal Province) regions described by Tully et al. (146). For more details, see Table S1. The map was created using the Positron base map available in QGIS (https://cartodb.com/basemaps/).”
EXTRACELLULAR ELECTRON TRANSFER
https://journals.asm.org/doi/10.1128/mbio.02904-21
https://discoverwildscience.com/the-microbes-that-breathe-metal
https://phys.org/news/2022-02-microbes-electrical-world-growth-power.html
Microbes establish electrical connection to outside world to generate growth power
by Harvard University / February 1, 2022
“Microbes may be miniscule, but they have a massive impact on Earth and its habitability. They are uniquely different from animals, plants, and other eukaryotic organisms in that they can gain energy from “breathing” a surprisingly wide range of surfaces and materials. Microbes also drastically reshape their environment as they feast on these energy sources, making microbes major players in the cycling and availability of nutrients on Earth. One especially well-known example was the rise of oxygen on Earth due to the metabolism of photosynthetic bacteria. In more recent years, scientists have discovered an astonishing new process by which microbes can “breathe” rocks through a process called extracellular electron transfer (EET). With EET microbes are able to “breathe” rocks and other materials that are outside their cell. In other words, microbes literally establish an electrical connection to the outside world, a connection they use to generate the power they need to grow. Researchers have since found groundbreaking uses for EET-capable microbes, such as aiding in toxic waste cleanup and as a source of alternative energy.
In a new study in mBio, researchers from Harvard and the University of Minnesota surveyed the tree of life in search of EET and discovered it is far more widespread than previously thought and is spread through horizontal gene transfer. One set of genes that makes EET possible, called mtrCAB, has been especially well-studied in the bacterium Shewanella oneidensis. Shewanella oneidensis was one of the first EET-capable organisms ever discovered. As such, it’s had a decades-long head start for the science community to interrogate it in the lab. “A lot of our understanding of mtrCAB comes from studies in this particular organism,” said co-lead author Isabel R. Baker, Ph.D. candidate in the Department of Organismic and Evolutionary Biology at Harvard. “But we don’t really know how widespread this type of metabolism is amongst all of life’s branches. Understanding how widespread it is will help us pinpoint where this kind of metabolism is at play in global biogeochemical cycles.”
Baker and co-senior author Professor Peter R. Girgus, also in the Department of Organismic and Evolutionary Biology at Harvard, were keen on partnering with University of Minnesota researchers co-senior author Professor Jeffrey A. Gralnick and co-lead author Bridget E. Conley. Gralnick and Conley are leading experts in EET research in Shewanella. Their previous work found that mtrCAB enables EET in at least two other species beyond Shewanella. In combining their expertise and a global database, the researchers found that these genes existed in far more organisms than previously assumed and in a wide variety of environments all over the world. “We found these genes in microbes all over the planet from virtually every kind of environment, including the deep sea, salt flats, oil refinery sites, the human gut, and even wastewater contaminated by the Manhattan project,” Baker said. Further analysis revealed that the set of genes were horizontally transferred extensively throughout the history of life. “The acquisition of genes is analogous to installing an app on your phone to give it a new functionality. Horizontal gene transfer is often associated with antibiotic resistance, but here we see a metabolic capability, EET, moving in and out of bacterial genomes,” Gralnick said. The researchers hypothesized that whenever the genes landed in different species, the genes involved in EET would change over time to better suit the new organism’s physiology and the environment it lived in.
“It’s sort of a foregone conclusion that microbes really shape our planet and EET had always been viewed as a niche ability,” Girguis said. “But we looked at all of the genomic information from animals, Archaea, and bacteria, and all other forms of life and found it’s far more widespread than previously assumed. All of the organisms we identified are capable of plugging directly into the substrates in their environment and changing what’s available there.” “The availability of these different substrates change over time as the Earth continues to evolve, either naturally or from human impact,” Baker said. “Understanding how these proteins may have coevolved with the history of oxygen on earth is very important. It could help us understand if this metabolism, or a metabolism like this, helped play a role in one of the massive transformations of our planet’s surface that gave rise to the modern world as we know it.”
More information: Isabel R. Baker et al, Evidence for Horizontal and Vertical Transmission of Mtr-Mediated Extracellular Electron Transfer among the Bacteria, mBio (2022). DOI: 10.1128/mbio.02904-21
PREVIOUSLY
LIVE WIRES
https://spectrevision.net/2019/07/04/live-wires/
MICROBES as GEOACTIVE AGENTS
https://spectrevision.net/2020/10/01/radical-geomycology/
LIFE WITHOUT SUNLIGHT
https://spectrevision.net/2021/06/01/subsurface-biomes/
METALLOPHYTE PLANTS
https://spectrevision.net/2021/08/16/metallophyte-plants/
LATERAL GENE TRANSFER
https://spectrevision.net/2023/12/14/horizontal-gene-transfer/
SOIL BATTERIES
https://spectrevision.net/2024/01/22/soil-batteries/