Oneidensis MR-1 Research Articles

Living Photovoltaics Based on Recombinant Expression of Mtra Decaheme in Photosynthetic Bacteria

At the center of microbial bioelectricity applications lies the critical need to express foreign heme proteins that are capable of redirecting the electron flux of the cell’s metabolism. This study presents a genetic construct for the heterologous expression of the periplasmatic decaheme MtrA c-type cytochrome from S. oneidensis MR-1, a dissimilatory metal-reducing exoelectrogen, inside the light-harvesting bacterium, Synechocystis sp. PCC 6803. Protein expression was verified through western-blotting and immunostaining, and oxygen evolution, optical density, and absorption measurements confirm sustained cell activity and viability under the tested expression conditions. Furthermore, the bioengineered cells show enhanced mediated exoelectrogenicity, as confirmed through a colorimetric iron assay and electrochemical measurements. Compared to wildtype cells on graphite electrodes, the bioengineered cells show a 2-fold increased extracellular electron transfer. The increased capacitance obtained under illumination and suppressed photocurrents in the presence of the photosynthetic inhibitor, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) suggest increased extraction of photosynthetically derived electrons from the recombinant cells. The improved bioelectricity transport across the outer membranes, as achieved through the heterologous heme expression inside cyanobacteria, presents new opportunities for re-wiring the metabolisms of light-harvesting microbes.

Feedback current production by a ferrous mediator revealing the redox properties of Shewanella oneidensis MR-1

• FcMeOH mediated electron transfer between Shewanella cells and electrodes. • A positive feedback current demonstrates that electron may transfer among cells. • Cyclic voltammetry reveals redox properties of S. oneidensis MR-1. • Electrons may transfer by spreading among redox flavocytochromes. The redox properties of electroactive bacteria play an important role in biogeochemical cycling, environmental remediation and bioenergy generation. But the detailed mechanisms on the redox properties of living cells are still vague. Herein, we designed a series of electrochemical tests mediated by FcMeOH to investigate the bacterial electrode process. Cyclic voltammograms and a positive feedback current production of scanning electrochemical microscopy provided evidence on the process of electrochemical oxidation followed by biocatalytic reduction. Moreover, an irreversible process for the redox behaviours of Shewanella oneidensis MR-1 revealed that electrons may transfer by spreading among redox flavocytochromes at the cell membrane and that these proteins may form a conductive network to perpetuate cathodic electron transfer. These results provide an insight into redox reactions at the microbe-electrode interface.

Repurposing CRISPR RNA-guided integrases system for one-step, efficient genomic integration of ultra-long DNA sequences.

Genomic integration techniques offer opportunities for generation of engineered microorganisms with improved or even entirely new functions but are currently limited by inability for efficient insertion of long genetic payloads due to multiplexing. Herein, using Shewanella oneidensis MR-1 as a model, we developed an optimized CRISPR-associated transposase from cyanobacteria Scytonema hofmanni (ShCAST system), which enables programmable, RNA-guided transposition of ultra-long DNA sequences (30 kb) onto bacterial chromosomes at ∼100% efficiency in a single orientation. In this system, a crRNA (CRISPR RNA) was used to target multicopy loci like insertion-sequence elements or combining I-SceI endonuclease, thereby allowing efficient single-step multiplexed or iterative DNA insertions. The engineered strain exhibited drastically improved substrate diversity and extracellular electron transfer ability, verifying the success of this system. Our work greatly expands the application range and flexibility of genetic engineering techniques and may be readily extended to other bacteria for better controlling various microbial processes.

Double Bacteria Synergistic Catalytic Reduction System for Heavy Metal Detoxification Treatment.

Synthetic biology has promoted the development of microbial therapy, but the scope of applicable microbial species is limited and transgenic microorganisms also display safety risks for in vivo applications. Interestingly, symbiotic microorganisms in nature can achieve functional updates by metabolic cooperation. Here, we report on a nongenetic method for engineering microorganisms to construct a heavy metal ion reduction system, which was prepared by linking Shewanella oneidensis MR-1 (SO) and Lactobacillus rhamnosus GG (LGG). SO could reduce metal ions but is limited by finite substrates in vivo. LGG could metabolize glucose to lactate as a substrate for SO, promoting extracellular electron transfer by SO and heavy metal ion reduction. Meanwhile, SO could generate electron donor cytochrome C to promote metabolism of LGG, forming metabolic synergy and circulation between these two bacteria. The SO-LGG system shows splendid ability to remove heavy metal ions and inflammatory modulation in acute or chronic heavy metal poisoning.

Performance and mechanisms exploration of nano zinc oxide (nZnO) on anaerobic decolorization by Shewanella oneidensis MR-1

Although the ecological safety of nanomaterials is of widespread concern, their current ambient concentrations are not yet sufficient to cause serious toxic effects. Thus, the nontoxic bioimpact of nanomaterials in wastewater treatment has attracted increasing attention. In this study, the effect of nano zinc oxide (nZnO), one of the most widely used nanomaterials, on the anaerobic biodegradation of methyl orange (MO) by Shewanella oneidensis MR-1 was comprehensively investigated. High-dosage nZnO (>0.5 mg/L) caused severe toxic stress on S. oneidensis MR-1, resulting in the decrease in decolorization efficiency. However, nZnO at ambient concentrations could act as nanostimulants and promote the anaerobic removal of MO by S. oneidensis MR-1, which should be attributed to the improvement of decolorization efficiency rather than cell proliferation. The dissolved Zn2+ was found to contribute to the bioeffect of nZnO on MO decolorization. Further investigation revealed that low-dosage nZnO could promote the cell viability, membrane permeability, anaerobic metabolism, as well as related gene expression, indicating that nZnO facilitated rather than inhibited the anaerobic wastewater treatment under ambient conditions. Thus, this work provides a new insight into the bioeffect of nZnO in actual environment and facilitates the practical application of nanomaterials as nanostimulants in biological process.

Determinants of Multiheme Cytochrome Extracellular Electron Transfer Uncovered by Systematic Peptide Insertion.

The multiheme cytochrome MtrA enables microbial respiration by transferring electrons across the outer membrane to extracellular electron acceptors. While structural studies have identified residues that mediate the binding of MtrA to hemes and to other cytochromes that facilitate extracellular electron transfer (EET), the relative importance of these interactions for EET is not known. To better understand EET, we evaluated how insertion of an octapeptide across all MtrA backbone locations affects Shewanella oneidensis MR-1 respiration on Fe(III). The EET efficiency was found to be inversely correlated with the proximity of the insertion to the heme prosthetic groups. Mutants with decreased EET efficiencies also arose from insertions in a subset of the regions that make residue-residue contacts with the porin MtrB, while all sites contacting the extracellular cytochrome MtrC presented high peptide insertion tolerance. MtrA variants having peptide insertions within the CXXCH motifs that coordinate heme cofactors retained some ability to support respiration on Fe(III), although these variants presented significantly decreased EET efficiencies. Furthermore, the fitness of cells expressing different MtrA variants under Fe(III) respiration conditions correlated with anode reduction. The peptide insertion profile, which represents the first comprehensive sequence-structure-function map for a multiheme cytochrome, implicates MtrA as a strategic protein engineering target for the regulation of EET.

The effect of riboflavin on the microbiologically influenced corrosion of pure iron by Shewanella oneidensis MR-1

The microbiologically influenced corrosion of pure iron was investigated in the presence of Shewanella oneidensis MR-1 with various levels of exogenous riboflavin (RF) serving as electron shuttles for extracellular electron transfer (EET). With more RF available, a larger and denser phosphate layer was formed on the surface of pure iron by the bacteria. The results of electrochemical impedance spectroscopy, linear polarization resistance and potentiodynamic polarization tests showed that the product layer provided good corrosion protection to the pure iron. Using electrochemical noise, we observed that the addition of RF accelerated the corrosion at the initial stage of immersion, thereby accelerating the deposition of products to form a protective layer subsequently.

Synthesis and Structure of a Two-Dimensional Palladium Oxide Network on Reduced Graphene Oxide.

New nanostructures often reflect new and exciting properties. Here, we present an two-dimensional, hitherto unreported PdO square network with lateral dimensions up to hundreds of nanometers growing on reduced graphene oxide (rGO), forming a hybrid nanofilm. An intermediate state of dissolved Pd(0) in the bacterium S. oneidensis MR-1 is pivotal in the biosynthesis and inspires an abiotic synthesis. The PdO network shows a lattice spacing of 0.5 nm and a thickness of 1.8 nm on both sides of an rGO layer and is proposed to be cubic or tetragonal crystal, as confirmed by structural simulations. A 2D silver oxide analog with a similar structure is also obtained using an analogous abiotic synthesis. Our study thus opens a simple route to a whole new class of 2D metal oxides on rGO as promising candidates for graphene superlattices with unexplored properties and potential applications for example in electronics, sensing, and energy conversion.

Effect of metal cations on antimicrobial activity and compartmentalization of silver in Shewanella oneidensis MR-1 upon exposure to silver ions

Silver is an antimicrobial agent that is used extensively in consumer products, such as fabrics and humidifiers. Silver ion (Ag+) uptake in bacteria represents a crucial phase of antimicrobial activity. However, the uptake mechanism of Ag+ in bacteria remains largely unknown. The genus Shewanella drives many geochemical processes of nutrients and pollutants in soils. In the present study, Ag+ uptake by Shewanella oneidensis MR-1 was first investigated in a laboratory in defined anaerobic, oligotrophic, and inorganic media with or without cations (potassium ions [K+], magnesium ions [Mg2+], and zinc ions [Zn2+]). Our results revealed variations in antimicrobial activity of Ag+ in the presence of Mg2+ and Zn2+. First, Mg2+ significantly decreased antimicrobial activity of Ag+ in S. oneidensis MR-1 by inhibiting cellular Ag+ uptake when compared with K+. The results were consistent with that of Co2+ (Mg2+ channel blocker) decreased Ag+ uptake by S. oneidensis MR-1. Moreover, Mg2+ promoted riboflavin secretion and facilitated the formation of metallic Ag nanoparticles on bacterial surfaces, which was beneficial for extracellular electron transfer and consequently reduced antibacterial activity of Ag+. Second, Zn2+ increased the antimicrobial activity of Ag+ in S. oneidensis MR-1, although the effect on Ag+ uptake was minimal. A synergistic interaction between Zn2+ and Ag+ led to an increase in dead cells and decreased ferrihydrite reduction capacity. The findings suggest that Mg2+ could reduce the environmental risk of Ag+ to soil bacteria, while Zn2+ should be of particular concern due to its synergistic antimicrobial effect on bacteria.

Type I-F CRISPR-PAIR platform for multi-mode regulation to boost extracellular electron transfer in Shewanella oneidensis

SummaryBio-electrochemical systems are based on extracellular electron transfer (EET), whose efficiency relates to the expression level of numerous genes. However, the lack of multi-functional tools for gene activation and repression hampers the enhancement of EET in electroactive microorganisms (EAMs). We thus develop a type I-F CRISPR/PaeCascade-RpoD-mediated activation and inhibition regulation (CRISPR-PAIR) platform in the model EAM, Shewanella oneidensis MR-1. Gene activation is achieved (3.8-fold) through fusing activator RpoD (σ70) to Cas7 when targeting the prioritized loci upstream of the transcription start site. Gene inhibition almost has no position preference when targeting the open reading frame, which makes the design of crRNAs easy and flexible. Then CRISPR-PAIR platform is applied to up-/down-regulate the expression of six endogenous genes, resulting in the improved EET efficiency. Moreover, simultaneous gene activation and inhibition are achieved in S. oneidensis MR-1. CRISPR-PAIR platform offers a programmable methodology for dual regulation, facilitating in-depth EET studies in Shewanella spp.

Insight into the magnetic properties of Pb-dopped iron oxide nanoparticles during Fe(III) bio-reduction by Shewanella oneidensis MR-1

Anthropogenic activities have led to a significant accumulation of Pb in the environment, posing a threat to ecosystems. Iron oxides that display magnetic properties are ubiquitous in the environment and Pb partitioning onto these minerals is considered one of the most critical geochemical processes controlling its environmental fate. In anoxic environments, iron oxides undergo redox cycling due to biotic and abiotic routes, resulting in their transformation/dissolution and evolution of their magnetic characteristics. However, there is still a lack of knowledge on the impact of Pb on the dynamic of iron oxides bioreduction. Furthermore, there is little information available regarding the nature of biogenic minerals and their magnetic signatures.Here we incubated Pb-bearing ferrihydrites (Fh_Pb) with various Pb/(Fe + Pb) molar ratios (i.e., 0, 2 and 5%) with the iron-reducing bacterium Shewanella oneidensis MR-1, for 21 days.XRD analyses of the initial Fh_Pb displayed characteristic features of Fh and a decrease of magnetization in the presence of Pb. During the bio-reduction process, Pb doping led to a drop in the rate and extent of reduction. At the end of the incubation period, the analysis of the aqueous solutions revealed a minor proportion of Pb in solution, indicating that a significant proportion of the Pb is sorbed onto the biogenic minerals. Magnetite (95%) and siderite (5%) formed during the bioreduction of Fh, while magnetite (~80%) and goethite (~20%) precipitated in the presence of Pb as revealed by transmission Mössbauer spectroscopy. Furthermore, the size of the magnetite particles decreased from about 11 nm in absence of Pb to 6 nm with 2% of Pb-bearing, while 5% of Pb led to particles too small to be quantified with our TEM measurements. The combined effect of the decrease in particle size of magnetite, substitution of Pb and the precipitation of goethite in the Pb-dopped assay led to a significant decrease of magnetization at room temperature. Overall, this study highlights the effect of Pb on iron oxides bio-reduction and transformation processes and the sensitivity of magnetism to serve as a monitoring method.

Bio-Nanohybrid Cell Based Signal Amplification System for Electrochemical Sensing.

A signal amplification system for electrochemical sensing was established by bio-nanohybrid cells (BNC) based on bacterial self-assembly and biomineralization. The BNC was constructed by partially encapsulating a Shewanella oneidensis MR-1 cell with the self-biomineralized iron sulfide nanoparticles. The iron sulfide nanoparticle encapsulated BNCs showed high transmembrane electron transfer efficiency and was explored as a superior redox cycling module. Impressively, by integrating this BNC redox cycling module into the electrochemical sensing system, the output signal was amplified over 260 times compared to that without the BNC module. Uniquely, with this BNC redox cycling system, ultrasensitive detection of riboflavin with an extremely low LOD of 0.2 nM was achieved. This work demonstrated the power of BNC in the area of biosensing and provided a new possibility for the design of a whole cell redox cycling based signal amplification system.

CRISPR/dCas9-RpoD-Mediated Simultaneous Transcriptional Activation and Repression in Shewanella oneidensis MR-1.

Extracellular electron transfer (EET) of electroactive microorganisms (EAMs) is the dominating factor for versatile applications of bio-electrochemical systems. Shewanella oneidensis MR-1 is one of the model EAMs for the study of EET, which is associated with a variety of cellular activities. However, due to the lack of a transcriptional activation tool, regulation of multiple genes is labor-intensive and time-consuming, which hampers the advancement of improving the EET efficiency in S. oneidensis. In this study, we developed an easily operated and multifunctional regulatory tool, that is, a simultaneous clustered regularly interspaced short palindromic repeats (CRISPR)-mediated transcriptional activation (CRISPRa) and interference (CRISPRi) system, for application in S. oneidensis. First, a large number of activators were screened, and RpoD (σ70) was determined as the optimal activator. Second, the effective activation range was identified to be 190-216 base upstream of the transcriptional start site. Third, up- and downregulation was achieved in concert by two orthogonal single guide RNAs targeting different positions. The activation of the cell division gene (minCDE) and repression of the cytotoxic gene (SO_3166) were concurrently implemented, increasing the power density by 2.5-fold and enhancing the degradation rate of azo dyes by 2.9-fold. The simultaneous CRISPRa and CRISPRi system enables simultaneous multiplex genetic regulation, offering the potential to further advance studies of the EET mechanism and application in S. oneidensis.

Pb-Bearing Ferrihydrite Bioreduction and Secondary-Mineral Precipitation during Fe Redox Cycling

The significant accumulation of Pb from anthropogenic activities threatens environmental ecosystems. In the environment, iron oxides are one of the main carriers of Pb. Thus, the redox cycling of iron oxides, which is due to biotic and abiotic pathways, and which leads to their dissolution or transformation, controls the fate of Pb. However, a knowledge gap exists on the bioreduction in Pb-bearing ferrihydrites, secondary-mineral precipitation, and Pb partitioning during the bioreduction/oxidation/bioreduction cycle. In this study, Pb-bearing ferrihydrite (Fh_Pb) with various Pb/(Fe+Pb) molar ratios (i.e., 0, 2, and 5%) were incubated with the iron-reducing bacterium Shewanella oneidensis MR-1 for 7 days, oxidized for 7 days (atmospheric O2), and bioreduced a second time for 7 days. Pb doping led to a drop in the rate and the extent of the reduction. Lepidocrocite (23–56%) and goethite (44–77%) formed during the first reduction period. Magnetite (72–84%) formed during the second reduction. The extremely-low-dissolved and bioavailable Pb concentrations were measured during the redox cycles, which indicates that the Pb significantly sorbed onto the minerals that were formed. Overall, this study highlights the influence of Pb and redox cycling on the bioreduction of Pb-bearing iron oxides, as well as on the nature of the secondary minerals that are formed.

Reconstruction of a Genome-Scale Metabolic Network for Shewanella oneidensis MR-1 and Analysis of its Metabolic Potential for Bioelectrochemical Systems.

Bioelectrochemical systems (BESs) based on Shewanella oneidensis MR-1 offer great promise for sustainable energy/chemical production, but the low rate of electron generation remains a crucial bottleneck preventing their industrial application. Here, we reconstructed a genome-scale metabolic model of MR-1 to provide a strong theoretical basis for novel BES applications. The model iLJ1162, comprising 1,162 genes, 1,818 metabolites and 2,084 reactions, accurately predicted cellular growth using a variety of substrates with 86.9% agreement with experimental results, which is significantly higher than the previously published models iMR1_799 and iSO783. The simulation of microbial fuel cells indicated that expanding the substrate spectrum of MR-1 to highly reduced feedstocks, such as glucose and glycerol, would be beneficial for electron generation. In addition, 31 metabolic engineering targets were predicted to improve electricity production, three of which have been experimentally demonstrated, while the remainder are potential targets for modification. Two potential electron transfer pathways were identified, which could be new engineering targets for increasing the electricity production capacity of MR-1. Finally, the iLJ1162 model was used to simulate the optimal biosynthetic pathways for six platform chemicals based on the MR-1 chassis in microbial electrosynthesis systems. These results offer guidance for rational design of novel BESs.

Customized Woven Carbon Fiber Electrodes for Bioelectrochemical Systems—A Study of Structural Parameters

Commercial carbon fiber (CF) fabrics are popular electrode materials for bioelectrochemical systems (BES), but are usually not optimized for the specific application. This study investigates BES-relevant material characteristics on fabric level, such as weave types and weave parameters. The two contrasting weave types plain and leno weave were characterized with respect to their envisaged application types: 1) BES with mainly advective flow regimes and 2) stirred systems, which could benefit from fluid flow through a fabric electrode. Experiments with batch and continuously fed pure cultures of Geobacter sulfurreducens PCA and Shewanella oneidensis MR-1 reveal that µm-scale electrode topologies are of limited use for the thick biofilms of G. sulfurreducens, but can boost S. oneidensis’ current generation especially in batch and fed-batch reactors. For advective flow regimes, deeper layers of biofilm inside microporous electrodes are often mass transport limited, even with thin biofilms of S. oneidensis. Therefore, low porosity plain weave electrodes for advective flow operation as in wastewater treating BES should be thin and flat. A trade-off between maximized current density and electrode material utilization exists, which is optimized exemplarily for an advective flow operation. For stirred BES of biotechnological applications, a flow-through of electrolyte is desired. For this, leno weave fabrics with pores at cm-scale are produced from 100% CF for the first time. In a preliminary evaluation, they outperform plain weave fabrics. Mass transfer investigations in stirred BES demonstrate that the large pores enable efficient electrode utilization at lower power input in terms of stirring speed.

Boosting microfluidic microbial fuel cells performance via investigating electron transfer mechanisms, metal-based electrodes, and magnetic field effect.

The presented paper fundamentally investigates the influence of different electron transfer mechanisms, various metal-based electrodes, and a static magnetic field on the overall performance of microfluidic microbial fuel cells (MFCs) for the first time to improve the generated bioelectricity. To do so, as the anode of microfluidic MFCs, zinc, aluminum, tin, copper, and nickel were thoroughly investigated. Two types of bacteria, Escherichia coli and Shewanella oneidensis MR-1, were used as biocatalysts to compare the different electron transfer mechanisms. Interaction between the anode and microorganisms was assessed. Finally, the potential of applying a static magnetic field to maximize the generated power was evaluated. For zinc anode, the maximum open circuit potential, current density, and power density of 1.39 V, 138,181 mA m-2 and 35,294 mW m-2 were obtained, respectively. The produced current density is at least 445% better than the values obtained in previously published studies so far. The microfluidic MFCs were successfully used to power ultraviolet light-emitting diodes (UV-LEDs) for medical and clinical applications to elucidate their application as micro-sized power generators for implantable medical devices.

Direct microbial electron uptake as a mechanism for stainless steel corrosion in aerobic environments

Shewanella oneidensis MR-1 is an attractive model microbe for elucidating the biofilm-metal interactions that contribute to the billions of dollars in corrosion damage to industrial applications each year. Multiple mechanisms for S. oneidensis-enhanced corrosion have been proposed, but none of these mechanisms have previously been rigorously investigated with methods that rule out alternative routes for electron transfer. We found that S. oneidensis grown under aerobic conditions formed thick biofilms (∼50 µm) on stainless steel coupons, accelerating corrosion over sterile controls. H2 and flavins were ruled out as intermediary electron carriers because stainless steel did not reduce riboflavin and previous studies have demonstrated stainless does not generate H2. Strain ∆mtrCBA, in which the genes for the most abundant porin-cytochrome conduit in S. oneidensis were deleted, corroded stainless steel substantially less than wild-type in aerobic cultures. Wild-type biofilms readily reduced nitrate with stainless steel as the sole electron donor under anaerobic conditions, but strain ∆mtrCBA did not. These results demonstrate that S. oneidensis can directly consume electrons from iron-containing metals and illustrate how direct metal-to-microbe electron transfer can be an important route for corrosion, even in aerobic environments.

Accelerating the extracellular electron transfer of Shewanella oneidensis MR-1 by carbon dots: The role of carbon dots concentration

The high performance of microbial extracellular electron transfer (EET) is essential for bioremediation and bioenergy generation. Carbon dots (CDs) modified electroactive microorganisms showed an increased electron transfer efficiency. However, the influence of CDs’ concentration the EET has not been illustrated before. Herein, we reported that the addition of CDs increased the current generation by accelerating the EET process. The maximum current output of microbial electrochemical cells with the addition of CDs was increased by more than 5 times compared to pure Shewanella oneidensis MR-1. With CDs addition, the increase of biofilm immobilization and flavins secretion improved the direct and mediated EET process. Electrochemical analyses clarified that the combination of cytochrome c with CDs resulted in a faster electron transfer rate. The overload of CDs would restrict their promotion effect on EET, which may be due to their biotoxicity to bacteria. This work offered the insight of CDs’ concentration on the efficiency of EET, not only promoting the related applications of EET but also inspiring the regulation of microorganism function via nanomaterial.

Single molecule tracking of bacterial cell surface cytochromes reveals dynamics that impact long-distance electron transport

Using a series of multiheme cytochromes, the metal-reducing bacterium Shewanella oneidensis MR-1 can perform extracellular electron transfer (EET) to respire redox-active surfaces, including minerals and electrodes outside the cell. While the role of multiheme cytochromes in transporting electrons across the cell wall is well established, these cytochromes were also recently found to facilitate long-distance (micrometer-scale) redox conduction along outer membranes and across multiple cells bridging electrodes. Recent studies proposed that long-distance conduction arises from the interplay of electron hopping and cytochrome diffusion, which allows collisions and electron exchange between cytochromes along membranes. However, the diffusive dynamics of the multiheme cytochromes have never been observed or quantified in vivo, making it difficult to assess their hypothesized contribution to the collision-exchange mechanism. Here, we use quantum dot labeling, total internal reflection fluorescence microscopy, and single-particle tracking to quantify the lateral diffusive dynamics of the outer membrane-associated decaheme cytochromes MtrC and OmcA, two key components of EET in S. oneidensis. We observe confined diffusion behavior for both quantum dot-labeled MtrC and OmcA along cell surfaces (diffusion coefficients DMtrC = 0.0192 ± 0.0018 µm2/s, DOmcA = 0.0125 ± 0.0024 µm2/s) and the membrane extensions thought to function as bacterial nanowires. We find that these dynamics can trace a path for electron transport via overlap of cytochrome trajectories, consistent with the long-distance conduction mechanism. The measured dynamics inform kinetic Monte Carlo simulations that combine direct electron hopping and redox molecule diffusion, revealing significant electron transport rates along cells and membrane nanowires.