In the quest for sustainable energy, scientists are turning to an unexpected ally: bacteria that consume metal.
These tiny organisms are at the heart of a technology that can clean wastewater while generating electricity.
Imagine a world where wastewater treatment plants not only purify water but also generate electricity. This isn't science fiction—it's the promise of microbial fuel cells (MFCs) powered by dissimilatory metal-reducing bacteria (DMRB). These remarkable microorganisms can transform organic waste into electrical energy while tackling environmental pollutants.
This article explores how these bacteria function as natural engineers, driving a technology that could revolutionize how we manage waste and produce energy.
Transforming organic pollutants into electricity
Cleaning wastewater while generating power
Dissimilatory metal-reducing bacteria are a group of microorganisms with a unique ability to "breathe" metals much like humans breathe oxygen. Found in various environments from river sediments to deep-sea vents, these bacteria use iron, manganese, and other metals as terminal electron acceptors during their respiration process under anaerobic conditions 7 .
Facultative anaerobe that can survive in both oxygen-rich and oxygen-poor environments 4 .
FlexibleStrict anaerobe that forms conductive biofilms and produces nanowires for electron transfer 4 .
SpecializedThe remarkable capability of DMRB to generate electricity stems from their unique electron transfer mechanisms:
Through conductive cellular extensions called "nanowires" or via direct contact between the cell surface and electrodes 2 4 .
Using natural electron shuttle compounds that transport electrons between cells and electrodes 2 .
Soluble molecules that carry electrons from cells to electrodes 1 .
To understand how DMRB perform in real-world conditions, let's examine a groundbreaking study that constructed a soil microbial fuel cell (SMFC) to remediate chromium-contaminated paddy soil while generating electricity 9 .
Voltage Production
Power Density
Cr(VI) Removal
| Parameter | CMFC (Closed-circuit) | OMFC (Open-circuit) | NMFC (No electrodes) |
|---|---|---|---|
| Voltage Production | 0.97 V | None | None |
| Power Density | 102.00 mW m⁻² | None | None |
| Cr(VI) Removal | 93.67% | Significantly lower | Significantly lower |
| Bioavailable Cr Reduction | 97.44% | Significantly lower | Significantly lower |
| Microbial Group | Role in SMFC | Abundance Increase | Function |
|---|---|---|---|
| Desulfotomaculum | Exoelectrogen | 3.32% in anode | Electricity generation |
| Hydrogenophaga | Cr(VI)-reducing bacteria | 2.07% in cathode | Chromium detoxification |
| Overall electroactive community | Multiple functions | >1000-fold enrichment | Combined remediation and power generation |
The implications of DMRB technology extend far beyond electricity generation. These bacteria show remarkable potential in addressing various environmental challenges:
DMRB can break down persistent chlorinated organic compounds used in industrial solvents—substances that are otherwise difficult to degrade and pose long-term environmental threats 2 . They achieve this through:
As demonstrated in our featured experiment, MFCs can effectively immobilize heavy metals like chromium 9 . Other studies show similar potential for cobalt, copper, vanadium, mercury, and various other heavy metals with removal efficiencies ranging from 25% to 99.95% .
DMRB can assist in valuable metal recovery from low-grade ores. For instance, they can extract nickel and cobalt from lateritic nickel ore by breaking down the iron oxide matrix that traps these valuable metals 4 . This offers a more sustainable alternative to traditional mining approaches.
Despite the promising potential, several challenges remain in scaling up MFC technology:
Dissimilatory metal-reducing bacteria represent a fascinating convergence of microbiology and electrochemistry. These tiny organisms offer a sustainable solution to multiple challenges simultaneously: treating wastewater, remediating contaminated environments, and generating clean electricity. As research advances, we move closer to harnessing the full potential of these microbial workhouses.
The science of DMRB reminds us that some of the most powerful solutions to our biggest challenges may come from the smallest life forms. In the intricate metabolism of metal-reducing bacteria, we find inspiration for a cleaner, more sustainable future.
For further reading on this topic, the scientific review "Harnessing the power: the role of dissimilatory metal-reducing bacteria in microbial fuel cells" (Chakraborty et al., 2025) provides comprehensive technical details on the mechanisms and applications of DMRB in bioelectrochemical systems 1 .