Periodic Reporting for period 1 - Cable electricity O2 (Harnessing the electric potential of cable bacteria to generate electricity sustainably)
Reporting period: 2023-08-01 to 2025-07-31
Summary of the context and overall objectives of the project
The focus of the project was on cable bacteria, long, multicellular bacteria that conduct electrons across centimeter distances in sediments. These bacteria are unique in biology and hold promise as living “wires.” We investigated how cable bacteria interact with electrodes and demonstrated that they can form stable connections with electronic materials. This work lays the foundation for biohybrid devices that merge biological electron transfer with modern technology.
The pathway to impact involves two key steps:
Fundamental discoveries – by identifying new microbial strategies for respiration and electricity transfer, the project advances our basic knowledge of life.
Application potential – by exploring integration of cable bacteria with electrodes, the project takes the first steps toward applications in biosensors, sustainable bioelectronics, and environmental technologies.
This research aligns with major European priorities, including the European Green Deal and Horizon Europe’s commitment to sustainable innovation. By deepening our understanding of microbes that link biology and electricity, the project contributes to the development of future clean technologies, while training the next generation of researchers in an emerging interdisciplinary field.
Another aspect of this project explored how microorganisms can transfer electricity and how this property can be harnessed to develop new technologies and address environmental challenges. Traditionally, microbes have been thought of as switching between aerobic (oxygen-based) and anaerobic (oxygen-free) lifestyles depending on environmental conditions. Our work overturns this view by showing that certain bacteria can combine both processes at the same time, offering new insights into microbial metabolism and evolution.
This discovery has significant implications for both science and society. From a scientific perspective, it opens a new chapter in microbiology by expanding our understanding of how life interacts with the environment at the level of electron flow. From an applied perspective, it suggests new opportunities in bioremediation, where bacteria could be used to clean up polluted environments under conditions previously thought unsuitable.
The pathway to impact involves two key steps:
Fundamental discoveries – by identifying new microbial strategies for respiration and electricity transfer, the project advances our basic knowledge of life.
Application potential – by exploring integration of cable bacteria with electrodes, the project takes the first steps toward applications in biosensors, sustainable bioelectronics, and environmental technologies.
This research aligns with major European priorities, including the European Green Deal and Horizon Europe’s commitment to sustainable innovation. By deepening our understanding of microbes that link biology and electricity, the project contributes to the development of future clean technologies, while training the next generation of researchers in an emerging interdisciplinary field.
Another aspect of this project explored how microorganisms can transfer electricity and how this property can be harnessed to develop new technologies and address environmental challenges. Traditionally, microbes have been thought of as switching between aerobic (oxygen-based) and anaerobic (oxygen-free) lifestyles depending on environmental conditions. Our work overturns this view by showing that certain bacteria can combine both processes at the same time, offering new insights into microbial metabolism and evolution.
This discovery has significant implications for both science and society. From a scientific perspective, it opens a new chapter in microbiology by expanding our understanding of how life interacts with the environment at the level of electron flow. From an applied perspective, it suggests new opportunities in bioremediation, where bacteria could be used to clean up polluted environments under conditions previously thought unsuitable.
Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far
The main activities carried out in the project were:
1. Cultivation and Characterization of Cable Bacteria in Synthetic Sediments
A major technical achievement was the successful cultivation of cable bacteria in defined synthetic sediments. Previously, growth relied on natural sediments, which introduced variability. Two reproducible sediment formulations were developed:
a sand–kaolinite–alpha cellulose mix, and
a pure alpha cellulose matrix.
Inoculation with Electronema aureum GS showed that the sand-based system reproduced the key biogeochemical fingerprints of cable bacteria, including sulfide oxidation and pH gradients. Microsensor profiling confirmed long-distance electron transport (LDET), the hallmark of cable bacteria activity.
Key achievements:
Long-term enrichment and subculturing of cable bacteria under controlled conditions.
Standardized synthetic medium eliminating inconsistencies from natural sediments.
Microsensor profiles (O2, sulfide, pH) matching natural sediment activity.
Microscopy and SEM confirmed multicellular filaments and conductive periplasmic fibers.
16S rRNA sequencing revealed co-existing sulfate-reducers and iron-reducers supporting cable bacteria metabolism.
This cultivation system provides a reliable experimental platform for future functional and genetic studies.
2. Mechanisms of Extracellular Electron Transfer (EET) in Cable Bacteria
Another major advance was the demonstration of cable bacteria interaction with electrodes in bioelectrochemical systems. Experiments under anoxic conditions revealed that cable bacteria are naturally attracted to electrodes poised at +0.25 V, producing significantly higher currents compared to controls.
Key findings:
Current generation in the presence of cable bacteria at +0.25 V.
Differential pulse voltammetry identified redox peaks (+0.25 V and +0.60 V) consistent with protein-mediated EET.
Elevated riboflavin concentrations suggested a role for flavins in electron transfer.
Redox activity was abolished by proteinase K treatment and heat, pointing to the involvement of extracytoplasmic redox proteins.
This provides the first evidence that cable bacteria possess protein-based extracellular electron transfer mechanisms, opening avenues for their use in microbial electrogenesis and bioelectronics.
3. Discovery of Simultaneous Aerobic and Anaerobic Respiration in Microbacterium, a bacerium in the vicinity of cable bacteria
The fellowship also led to the discovery of a previously unrecognized metabolic capacity in Microbacterium deferre sp. nov. A1-JK. Unlike the long-held dogma that bacteria switch between aerobic and anaerobic lifestyles, this strain was shown to perform both aerobic respiration and anaerobic iron reduction simultaneously.
This overturns a central paradigm in microbiology and provides new insights into microbial evolution and ecology. Beyond basic science, this capacity could be exploited for bioremediation, enabling pollutant degradation in fluctuating oxygen environments where conventional strategies fail.
Environmental and Biotechnological Implications
Together, these results contribute to three major fields:
Microbial ecology – reproducible cultivation and characterization of cable bacteria under laboratory conditions.
Electromicrobiology – identification of redox proteins and flavins mediating extracellular electron transfer.
Environmental biotechnology – discoveries with direct implications for pollutant remediation, methane mitigation, and the development of biohybrid devices that integrate microbial electron transfer with electrodes.
These achievements establish a scientific foundation for bioelectrochemical applications, from sustainable sensors to environmental cleanup, while opening a new frontier in understanding microbial metabolism.
1. Cultivation and Characterization of Cable Bacteria in Synthetic Sediments
A major technical achievement was the successful cultivation of cable bacteria in defined synthetic sediments. Previously, growth relied on natural sediments, which introduced variability. Two reproducible sediment formulations were developed:
a sand–kaolinite–alpha cellulose mix, and
a pure alpha cellulose matrix.
Inoculation with Electronema aureum GS showed that the sand-based system reproduced the key biogeochemical fingerprints of cable bacteria, including sulfide oxidation and pH gradients. Microsensor profiling confirmed long-distance electron transport (LDET), the hallmark of cable bacteria activity.
Key achievements:
Long-term enrichment and subculturing of cable bacteria under controlled conditions.
Standardized synthetic medium eliminating inconsistencies from natural sediments.
Microsensor profiles (O2, sulfide, pH) matching natural sediment activity.
Microscopy and SEM confirmed multicellular filaments and conductive periplasmic fibers.
16S rRNA sequencing revealed co-existing sulfate-reducers and iron-reducers supporting cable bacteria metabolism.
This cultivation system provides a reliable experimental platform for future functional and genetic studies.
2. Mechanisms of Extracellular Electron Transfer (EET) in Cable Bacteria
Another major advance was the demonstration of cable bacteria interaction with electrodes in bioelectrochemical systems. Experiments under anoxic conditions revealed that cable bacteria are naturally attracted to electrodes poised at +0.25 V, producing significantly higher currents compared to controls.
Key findings:
Current generation in the presence of cable bacteria at +0.25 V.
Differential pulse voltammetry identified redox peaks (+0.25 V and +0.60 V) consistent with protein-mediated EET.
Elevated riboflavin concentrations suggested a role for flavins in electron transfer.
Redox activity was abolished by proteinase K treatment and heat, pointing to the involvement of extracytoplasmic redox proteins.
This provides the first evidence that cable bacteria possess protein-based extracellular electron transfer mechanisms, opening avenues for their use in microbial electrogenesis and bioelectronics.
3. Discovery of Simultaneous Aerobic and Anaerobic Respiration in Microbacterium, a bacerium in the vicinity of cable bacteria
The fellowship also led to the discovery of a previously unrecognized metabolic capacity in Microbacterium deferre sp. nov. A1-JK. Unlike the long-held dogma that bacteria switch between aerobic and anaerobic lifestyles, this strain was shown to perform both aerobic respiration and anaerobic iron reduction simultaneously.
This overturns a central paradigm in microbiology and provides new insights into microbial evolution and ecology. Beyond basic science, this capacity could be exploited for bioremediation, enabling pollutant degradation in fluctuating oxygen environments where conventional strategies fail.
Environmental and Biotechnological Implications
Together, these results contribute to three major fields:
Microbial ecology – reproducible cultivation and characterization of cable bacteria under laboratory conditions.
Electromicrobiology – identification of redox proteins and flavins mediating extracellular electron transfer.
Environmental biotechnology – discoveries with direct implications for pollutant remediation, methane mitigation, and the development of biohybrid devices that integrate microbial electron transfer with electrodes.
These achievements establish a scientific foundation for bioelectrochemical applications, from sustainable sensors to environmental cleanup, while opening a new frontier in understanding microbial metabolism.
Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)
Results Beyond the State of the Art
1. Advancing Cultivation of Cable Bacteria with Synthetic Sediments
One of the most significant advancements achieved in this work is the development of a defined synthetic sediment mix for cable bacteria cultivation. Prior to this study, research relied heavily on natural sediments, which introduced variability and limited reproducibility across laboratories. The use of synthetic sediments eliminates geographical and seasonal variation, enabling standardized protocols.
Key Innovations and Impact:
Successful subculturing of cable bacteria in a controlled artificial sediment matrix.
Establishment of reproducible biogeochemical gradients (oxygen, sulfide, pH) in synthetic sediments.
Potential for high-throughput studies of cable bacteria physiology and metabolism.
Foundation for genetic and metabolic studies previously hampered by cultivation challenges.
2. Unveiling Novel Extracellular Electron Transfer (EET) Mechanisms in Cable Bacteria
This study revealed previously unknown extracellular electron transfer (EET) processes in cable bacteria, demonstrating that they not only perform long-distance electron transport (LDET) in sediments but also directly interact with electrodes in bioelectrochemical systems.
Breakthrough Findings and Impact:
Identification of redox-active proteins associated with electrode interactions.
Discovery of redox peaks at +0.25 V and +0.60 V, indicating active electron transfer pathways.
Evidence for flavins as mediators of electron transport.
Enhanced current generation in bioelectrochemical setups containing cable bacteria.
Future Applications:
Deployment in microbial fuel cells and electrosynthesis platforms.
Exploration of donor–acceptor flexibility for novel bioremediation and energy technologies.
Potential use in bioelectronics.
3. Discovery of Simultaneous Aerobic and Anaerobic Respiration in Microbacterium
A transformative finding of this project was the identification of a novel Gram-positive bacterium, Microbacterium deferre sp. nov. A1-JK, capable of performing aerobic respiration and anaerobic iron reduction simultaneously. This challenges the long-standing paradigm that microbes switch between metabolic modes depending on oxygen availability.
Novelty and Scientific Impact:
Experimental evidence of simultaneous aerobic and anaerobic respiration in a single organism along with biochemical mechanisms enabling it.
Revision of textbook understanding of microbial physiology and evolution.
Potential Applications:
Bioremediation – exploitation of Microbacterium for pollutant degradation in fluctuating redox environments (e.g. contaminated soils, sediments).
Environmental resilience – capacity to sustain metabolism under oxygen-variable conditions, relevant for industrial wastewater treatment.
Fundamental microbiology – opens new avenues for studying evolutionary pressures shaping dual respiration strategies.
Future Research Needs:
Genomic and proteomic dissection of the molecular mechanisms underpinning dual respiration.
Exploration of ecological niches where such dual metabolism provides a selective advantage.
Investigation of bioengineering potential for hybrid aerobic–anaerobic bioprocesses.
5. Summary of Results and Future Prospects
This fellowship achieved results that move beyond the state of the art by:
Establishing reproducible cultivation of cable bacteria in defined synthetic sediments, which was not achieved so far.
Providing the first direct evidence of electrode interactions and protein-mediated EET in cable bacteria. Demonstrating the interaction of living cable bacteria on electrodes.
Discovering a novel metabolic paradigm: simultaneous aerobic–anaerobic respiration in Microbacterium.
Demonstrating high potential for environmental and bioelectrochemical applications.
By bridging microbial ecology, electromicrobiology, and applied biotechnology, the project has paved the way for new microbial technologies at the interface of energy, environment, and sustainability.
1. Advancing Cultivation of Cable Bacteria with Synthetic Sediments
One of the most significant advancements achieved in this work is the development of a defined synthetic sediment mix for cable bacteria cultivation. Prior to this study, research relied heavily on natural sediments, which introduced variability and limited reproducibility across laboratories. The use of synthetic sediments eliminates geographical and seasonal variation, enabling standardized protocols.
Key Innovations and Impact:
Successful subculturing of cable bacteria in a controlled artificial sediment matrix.
Establishment of reproducible biogeochemical gradients (oxygen, sulfide, pH) in synthetic sediments.
Potential for high-throughput studies of cable bacteria physiology and metabolism.
Foundation for genetic and metabolic studies previously hampered by cultivation challenges.
2. Unveiling Novel Extracellular Electron Transfer (EET) Mechanisms in Cable Bacteria
This study revealed previously unknown extracellular electron transfer (EET) processes in cable bacteria, demonstrating that they not only perform long-distance electron transport (LDET) in sediments but also directly interact with electrodes in bioelectrochemical systems.
Breakthrough Findings and Impact:
Identification of redox-active proteins associated with electrode interactions.
Discovery of redox peaks at +0.25 V and +0.60 V, indicating active electron transfer pathways.
Evidence for flavins as mediators of electron transport.
Enhanced current generation in bioelectrochemical setups containing cable bacteria.
Future Applications:
Deployment in microbial fuel cells and electrosynthesis platforms.
Exploration of donor–acceptor flexibility for novel bioremediation and energy technologies.
Potential use in bioelectronics.
3. Discovery of Simultaneous Aerobic and Anaerobic Respiration in Microbacterium
A transformative finding of this project was the identification of a novel Gram-positive bacterium, Microbacterium deferre sp. nov. A1-JK, capable of performing aerobic respiration and anaerobic iron reduction simultaneously. This challenges the long-standing paradigm that microbes switch between metabolic modes depending on oxygen availability.
Novelty and Scientific Impact:
Experimental evidence of simultaneous aerobic and anaerobic respiration in a single organism along with biochemical mechanisms enabling it.
Revision of textbook understanding of microbial physiology and evolution.
Potential Applications:
Bioremediation – exploitation of Microbacterium for pollutant degradation in fluctuating redox environments (e.g. contaminated soils, sediments).
Environmental resilience – capacity to sustain metabolism under oxygen-variable conditions, relevant for industrial wastewater treatment.
Fundamental microbiology – opens new avenues for studying evolutionary pressures shaping dual respiration strategies.
Future Research Needs:
Genomic and proteomic dissection of the molecular mechanisms underpinning dual respiration.
Exploration of ecological niches where such dual metabolism provides a selective advantage.
Investigation of bioengineering potential for hybrid aerobic–anaerobic bioprocesses.
5. Summary of Results and Future Prospects
This fellowship achieved results that move beyond the state of the art by:
Establishing reproducible cultivation of cable bacteria in defined synthetic sediments, which was not achieved so far.
Providing the first direct evidence of electrode interactions and protein-mediated EET in cable bacteria. Demonstrating the interaction of living cable bacteria on electrodes.
Discovering a novel metabolic paradigm: simultaneous aerobic–anaerobic respiration in Microbacterium.
Demonstrating high potential for environmental and bioelectrochemical applications.
By bridging microbial ecology, electromicrobiology, and applied biotechnology, the project has paved the way for new microbial technologies at the interface of energy, environment, and sustainability.