Addressing this critical knowledge gap, researchers employed state-of-the-art cryo-electron microscopy (cryo-EM) techniques to capture high-resolution snapshots of Na⁺-NQR at various stages of its catalytic cycle. Co-first author Moe Ishikawa-Fukuda led the cryo-EM efforts, which revealed dynamic conformational changes in the enzyme’s structure concurrent with electron transport. These conformational shifts were then subjected to rigorous molecular dynamics simulations, conducted by co-first author Takehito Seki, providing a comprehensive mechanistic framework for how electron flow drives sodium translocation.

The study showed that electron transfer within the enzyme prompts conformational rearrangements that modulate an internal gating mechanism. This gate essentially opens and closes a channel embedded in the bacterial membrane, permitting sodium ions to selectively move across the membrane. This movement is tightly coupled to the redox chemistry taking place, translating the energy released from electron transfer directly into mechanical work essential for bacterial bioenergetics. Such mechanistic insight addresses a longstanding question in microbiology and bioenergetics, elucidating how these sodium pumps function distinctly from the more widely studied proton pumps found in mitochondria of higher organisms.

One unexpected discovery during this investigation involved a natural inhibitor called korormicin, which the team had identified in earlier studies. Korormicin proved instrumental in stabilizing otherwise transient intermediate states of the Na⁺-NQR complex, thus enabling the researchers to capture structural images that have historically been difficult to obtain. This finding not only underscores the utility of korormicin as a molecular probe but also indicates potential pathways for pharmacological intervention.

These revelations offer compelling possibilities for medical science, particularly in the context of antibiotic development. Since the sodium pumping mechanism in these bacteria exhibits fundamental differences from human cellular machinery, drugs targeting Na⁺-NQR could achieve selective inhibition without adverse effects on human cells. The Kyoto University team plans to explore whether the intermediate conformational states they have elucidated can serve as effective drug targets, potentially paving the way for novel classes of antibiotics that circumvent resistance mechanisms plaguing existing treatments.

Moreover, this research sheds light on a broader principle of energy conversion in biological systems: the direct coupling of redox chemistry to ion transport in membrane proteins. Unlike the classical proton pumps driven by proton gradients, the redox-driven sodium pumping mechanism represents a unique biochemical strategy employed by diverse bacterial species. Understanding this system could inspire biomimetic designs in synthetic biology and nanotechnology, where harnessing efficient ion transport is a key challenge.

The findings also prompt a reevaluation of bacterial energy metabolism frameworks, particularly in pathogenic strains such as Vibrio cholerae, the causative agent of cholera, which relies on Na⁺-NQR for survival and virulence. Detailed insights into Na⁺-NQR structure and function may thus have implications extending beyond basic science, influencing public health strategies and the development of antibacterial agents targeting this critical respiratory enzyme.

This novel research brings into focus the power of integrating cutting-edge experimental methodologies like cryo-EM with computational approaches such as molecular modeling to illuminate previously inaccessible molecular processes. The dynamic picture attained by capturing enzyme states in motion marks a significant advance over static structural studies, offering a time-resolved perspective on how proteins harness chemical energy to perform essential cellular work.

Kyoto University, with a rich history of scientific excellence and innovation, spearheaded this collaborative effort involving researchers from multiple institutes including Rensselaer Polytechnic Institute, the Kyoto Institute of Technology, and the Institute for Molecular Science. Supported through grants from premier funding bodies such as the Japan Society for the Promotion of Science and the NIH, this work exemplifies the productive convergence of international expertise and multidisciplinary approaches.

Quote from Ishikawa-Fukuda encapsulates the study’s impact succinctly: “Our study is the first to clearly explain how redox reactions directly drive sodium ion transport at the molecular level, providing a new framework for understanding energy conversion in bacteria.” Similarly, Seki highlights the distinctiveness of the sodium pump mechanism, noting it “addresses a long-standing question in bioenergetics, revealing a strategy fundamentally different from the proton pump found in mammalian mitochondria.”

Looking forward, the team aims to translate their molecular insights into practical applications, with hopes of discovering small molecules capable of selectively inhibiting the sodium pump’s function. Success in such endeavors could lead to next-generation antibiotics tailored to combat bacteria by disabling their energy machinery, thus crippling their viability without harming beneficial microbial communities or human cells.

In summary, the elucidation of Na⁺-NQR structure-function relationships constitutes a major leap forward in microbiology and structural biology. It highlights the elegance of biological energy transduction and opens fresh avenues for therapeutic exploration. As antibiotic resistance continues to rise globally, new strategies premised on detailed molecular understanding are vital—and this study provides a robust foundation for such innovation in bacterial bioenergetics.

Subject of Research: Cells

Article Title: The redox driven Na+-pumping mechanism in Vibrio cholerae NADH-quinone oxidoreductase relies on dynamic conformational changes

News Publication Date: 12-Feb-2026

Web References: http://dx.doi.org/10.1038/s41467-026-69182-w

References: The redox driven Na+-pumping mechanism in Vibrio cholerae NADH-quinone oxidoreductase relies on dynamic conformational changes, Nature Communications, DOI: 10.1038/s41467-026-69182-w, published 12 February 2026.

Image Credits: Moe Ishikawa-Fukuda

Keywords: Bacteria, Bacterial genomes, Sodium channels, Ion channels, Oxygen reduction

Cable bacteria, known for their distinctive filamentous structure composed of rod-shaped cells connected end-to-end, possess a unique feature: long conductive fibers embedded within their outer membranes that facilitate electron transport. These fibers enable the bacteria to establish an electrical connection between electron donors in deeper sediment layers, such as sulfide, and electron acceptors near the surface, like oxygen or nitrate. This remarkable mechanism allows the bacteria to efficiently drive redox reactions across spatial gradients that are often separated by centimeters, an adaptation that significantly enhances their survival in sedimentary ecosystems.

The newly discovered species exhibits a morphological and genomic uniqueness that distinguishes it from previously characterized cable bacteria. Unlike other species within the Ca. Electrothrix genus, Ca. Electrothrix yaqonensis features pronounced surface ridges up to three times wider than those found in other cable bacteria. These ridges are not merely structural quirks but house highly conductive fibers composed of nickel-based molecules—a feature that is as rare as it is fascinating in the microbial world. This distinctive anatomy suggests an evolutionary adaptation aimed at optimizing electron conductivity and metabolic efficiency under specific environmental conditions.

Genomic analysis of Ca. Electrothrix yaqonensis reveals a blend of metabolic pathways that bridge the previously known genera Ca. Electrothrix and Ca. Electronema, suggesting it occupies an early evolutionary branch within the Electrothrix clade. This phylogenetic position can provide critical insights into how cable bacteria diversified their electron transport capabilities and adapted to a variety of ecological niches. Such knowledge could help unravel the evolutionary pressures that shaped these complex conduction systems and inspire bioengineering efforts to emulate their functionality.

Electron transport in cable bacteria operates through reduction-oxidation (redox) reactions, where electrons generated during the oxidation of sulfide deep within sediments are transported to the surface, where they are accepted by oxygen or nitrate. This long-range electron conduction system prevents the build-up of toxic compounds like sulfide in sediment layers and influences the cycling of nutrients essential for aquatic ecosystems. The metabolic efficiency afforded by this electron transport capacity not only benefits the bacteria but also has broader geochemical implications in sediment environments.

The presence of nickel-containing conductive fibers within Ca. Electrothrix yaqonensis is of particular scientific interest. Nickel is a transition metal known for its redox versatility and ability to facilitate electron transfer processes. Unlike the more commonly studied iron-containing cytochromes typically found in microbial electron transport chains, these nickel-based proteins in cable bacteria represent an alternative biochemical strategy for conduction. Understanding the structure-function relationship of these fibers at the molecular level could open up entirely new avenues for the design of bioinspired conductive materials.

From a practical standpoint, the unique electron transport capabilities of these cable bacteria could be harnessed for environmental cleanup technologies. Their natural conductive filaments can facilitate the transfer of electrons required to reduce and neutralize various sediment-bound pollutants. For example, they could enhance the bioremediation of heavy metals or organic contaminants by accelerating redox reactions that convert harmful substances into inert forms. This intrinsic connection between microbial metabolism and sediment chemistry positions cable bacteria as vital players in maintaining environmental health.

Moreover, the scalable biological conductivity inherent to cable bacteria presents exciting possibilities in the emerging field of bioelectronics. Harnessing or mimicking the nickel-based conductive fibers found in Ca. Electrothrix yaqonensis could inspire new generations of biohybrid devices that transcend traditional silicon-based electronics. Such devices could operate in aqueous or biological environments, enabling minimally invasive medical sensors, real-time environmental monitoring systems, or novel energy storage solutions rooted in biological principles.

The discovery of Ca. Electrothrix yaqonensis also resonates culturally. The species’ name honors the Yaqona people, indigenous inhabitants whose ancestral lands encompass Yaquina Bay, where the bacteria were first isolated. This naming serves as a tribute to the long-standing relationship between native communities and their natural environment, and reflects a growing recognition of indigenous contributions to ecological knowledge and environmental stewardship.

This research was led by Cheng Li, who conducted the work as a postdoctoral scholar at Oregon State University and will soon return as an assistant professor in the College of Agricultural Sciences. Collaborators included Clare Reimers, a distinguished emerita professor at OSU, as well as scientists from the University of Antwerp, Delft University of Technology, and the University of Vienna. Their multi-institutional effort was supported by agencies like the Office of Naval Research, Oregon Sea Grant, and numerous European research foundations.

The team’s discovery was published in the latest volume of Applied and Environmental Microbiology, detailing the extensive observational studies and genomic analyses that underpin their findings. This work marks a significant step forward in understanding the complex physiology of cable bacteria and highlights the potential biotechnological applications of microbial electron transport mechanisms.

The identification of Ca. Electrothrix yaqonensis underscores the power of interdisciplinary collaboration and modern molecular techniques to uncover novel life forms with transformative potential. As researchers continue to explore the diversity of cable bacteria in various ecosystems, they anticipate uncovering more species with unique conductive properties and ecological roles, each contributing to the intricate web of life beneath our feet.

In sum, this discovery presents a remarkable confluence of microbiology, bioelectrochemistry, and environmental science, inviting us to rethink the boundaries between biological and electronic systems. Ca. Electrothrix yaqonensis is not only a testament to microbial ingenuity but a promising blueprint for future technologies that marry living systems with human innovation in unprecedented ways.

Subject of Research: Animals

Article Title: A novel cable bacteria species with a distinct morphology and genomic potential

News Publication Date: 22-Apr-2025

Web References: 10.1128/aem.02502-24

Image Credits: Provided by Cheng Li

Keywords: Cable bacteria, bioelectronics, electron transport, nickel-based conductive fibers, sediment geochemistry, bioremediation, microbial electron conduction, Ca. Electrothrix yaqonensis, microbial metabolism, biohybrid devices, environmental monitoring, microbial evolution