Complete genome sequence of Geobacter sp. strain 60473, an electrochemically active bacterium isolated from lakeshore mud.

Geobacter sp. strain 60473 is an electrochemically active bacterium (EAB) isolated from mud taken from the shore of lake Suwa in Japan. Here, we report the complete genome sequence of strain 60473, which helps deepen our understanding of common and strain-specific genomic features of EAB affiliated with the genus Geobacter.

Engineering a highly durable adeno-associated virus receptor for analytical applications.

Adeno-associated virus (AAV) is a major viral vector used in gene therapy. There are multiple AAV serotypes, and many engineered AAV serotypes are developed to alter their tissue tropisms with capsid modification. The universal AAV receptor (AAVR) is an essential receptor for multiple AAV serotypes. Since most AAV serotypes used in gene therapy infect cells via interaction with AAVR, the quantification of the vector-binding ability of AAV to AAVR could be an important quality check for therapeutic AAV vectors. To enable a steady evaluation of the AAV-AAVR interaction, we created an engineered AAVR through mutagenesis. Engineered AAVR showed high durability against acid while retaining its AAV-binding activity. An affinity chromatography column with the engineered AAVR was also developed. This column enabled repeated binding and acid dissociation measurements of AAVR with various AAV serotypes. Our data showed that the binding affinities of AAV2 to AAVR were diverse among serotypes, providing insight into the relationship with the infection efficiency of AAV vectors. Thus, this affinity column can be used in process development for quality checks, quantitating capsid titers, and affinity purification of AAV vectors. Furthermore, this column may serve as a useful tool in novel AAV vector capsid engineering.

Using Video Calls to Reduce Risky Behaviors and Enhance Instruction Understanding of Patients in Acute Care Hospitals During the COVID-19 Pandemic.

Backgrounds During the COVID-19 pandemic, visitor restrictions in healthcare settings adversely affected patients. Video calls have emerged as an essential digital alternative that can decrease patients' anxiety and improve satisfaction. This study investigated whether family-initiated video calls could mitigate delirium symptoms and risky behaviors and enhance patients' comprehension of instructions. Methods This observational study used medical chart data and the Diem Payment System from a single acute care hospital in Fukuoka, Japan. The study involved patients hospitalized between May 2020 and August 2021 who used video chat systems. Patients or their relatives used video calls through Skype. The frequency of video chat use served as the primary exposure. Changes in the patients' risky behaviors and instruction comprehension upon discharge were the primary outcomes. Results A total of 532 patients were included in the study, with an average age of over 70 years. After implementing the inverse probability of treatment weighting adjustment, an improved balance across age, sex, BMI categories, and other variables was observed. The effects of video calls on risky behaviors and instruction comprehension varied. Patients with three or more video calls showed distinct effects compared with those with fewer calls. When hospitalization was limited to three weeks, video calls noticeably influenced risky behaviors (p=0.022, 95% CI:1.08-2.63), but not instruction comprehension (p=0.226, 95% CI:0.43-1.22). Conclusions The use of video calls as a visitation method in acute care hospitals during a pandemic suggests that video calls reduce risky behaviors in patients with a three-week stay. This alternative to physical visitations contributes positively to patient safety and supports ongoing efforts to prevent the spread of COVID-19.

Improved electrochemical properties of graphite electrodes incubated with iron powders in rice-paddy fields boost power outputs from microbial fuel cells.

Studies have shown that the supplementation of anode-surrounding soil with zero-valent iron (ZVI) boosts power outputs from rice paddy-field microbial fuel cells (RP-MFCs). In order to understand mechanisms by which ZVI boosts outputs from RP-MFCs, the present study operated RP-MFCs with and without ZVI, and compositions of anode-associated bacteria and electrochemical properties of graphite anodes were analyzed after 3-month operation. Metabarcoding using 16S rRNA gene fragments showed that bacterial compositions did not largely differ among these RP-MFCs. Cyclic voltammetry showed improved electrochemical properties of anodes recovered from ZVI-supplemented RP-MFCs, and this was attributed to the adhesion of iron-oxide films onto graphite surfaces. Bioelectrochemical devices equipped with graphite anodes recovered from ZVI-supplemented RP-MFCs generated higher currents than those with fresh graphite anodes. These results suggest that ZVI is oxidized to iron oxides in paddy-field soil and adheres onto graphite anodes, resulting in the boost of power outputs from RP-MFCs.

Bioaugmentation of microbial electrolysis cells with Geobacter sulfurreducens YM18 for enhanced hydrogen production from starch.

Double-chamber microbial electrolysis cells (MECs) were operated using starch-based medium as the anolyte and rice paddy-field soil as the anode inoculum, and hydrogen production from the cathode chamber was examined. In order to enhance current generation and hydrogen production, the anode chamber was bioaugmented with Geobacter sulfurreducens strain YM18, and its effects were evaluated based on the performances of non-bioaugmented controls. Results show that the bioaugmented MEC generated threefold greater current during one-month operation and produced sixfold greater amounts of hydrogen than those of the non-bioaugmented control. Quantitative PCR and metabarcoding analyses confirmed successful colonization of anode surfaces with YM18, suggesting the utility of bioaugmentation with YM18 for enhancing the performance of bioelectrochemical systems, including MECs treating biomass wastes.

Supplementation with Amino Acid Sources Facilitates Fermentative Growth of Shewanella oneidensis MR-1 in Defined Media.

Shewanella oneidensis MR-1 is a facultative anaerobe that grows by respiration using a variety of electron acceptors. This organism serves as a model to study how bacteria thrive in redox-stratified environments. A glucose-utilizing engineered derivative of MR-1 has been reported to be unable to grow in glucose minimal medium (GMM) in the absence of electron acceptors, despite this strain having a complete set of genes for reconstructing glucose to lactate fermentative pathways. To gain insights into why MR-1 is incapable of fermentative growth, this study examined a hypothesis that this strain is programmed to repress the expression of some carbon metabolic genes in the absence of electron acceptors. Comparative transcriptomic analyses of the MR-1 derivative were conducted in the presence and absence of fumarate as an electron acceptor, and these found that the expression of many genes involved in carbon metabolism required for cell growth, including several tricarboxylic acid (TCA) cycle genes, was significantly downregulated in the absence of fumarate. This finding suggests a possibility that MR-1 is unable to grow fermentatively on glucose in minimal media owing to the shortage of nutrients essential for cell growth, such as amino acids. This idea was demonstrated in subsequent experiments that showed that the MR-1 derivative fermentatively grows in GMM containing tryptone or a defined mixture of amino acids. We suggest that gene regulatory circuits in MR-1 are tuned to minimize energy consumption under electron acceptor-depleted conditions, and that this results in defective fermentative growth in minimal media. IMPORTANCE It is an enigma why S. oneidensis MR-1 is incapable of fermentative growth despite having complete sets of genes for reconstructing fermentative pathways. Understanding the molecular mechanisms behind this defect will facilitate the development of novel fermentation technologies for the production of value-added chemicals from biomass feedstocks, such as electro-fermentation. The information provided in this study will also improve our understanding of the ecological strategies of bacteria living in redox-stratified environments.

Electrogenetic control of gene expression in Shewanella oneidensis MR-1 using Arc-dependent transcriptional promoters.

Electrochemically active bacteria (EAB) are capable of electrically interacting with electrodes, enabling their application in bioelectrochemical systems (BESs). As the performance of BES is related to the metabolic activities of EAB, the development of methods to control their metabolic activities is important to facilitate BES applications. A recent study found that the EAB Shewanella oneidensis MR-1 uses the Arc system to regulate the expression of catabolic genes in response to electrode potentials, suggesting that a methodology for electrical control of gene expression in EAB, referred to as electrogenetics, can be developed by using electrode potential-responsive, Arc-dependent transcriptional promoters. Here, we explored Arc-dependent promoters in the genomes of S. oneidensis MR-1 and Escherichia coli to identify electrode potential-responsive promoters that are differentially activated in MR-1 cells exposed to high- and low-potential electrodes. LacZ reporter assays using electrode-associated cells of MR-1 derivatives revealed that the activities of promoters located upstream of the E. coli feo gene (Pfeo) and the MR-1 nqrA2 (SO_0902) gene (Pnqr2) were significantly increased when S. oneidensis cells were exposed to electrodes poised at +0.7 V and -0.4 V (versus the standard hydrogen electrode), respectively. Additionally, we developed a microscopic system for in situ monitoring of promoter activity in electrode-associated cells and found that Pnqr2 activity was persistently induced in MR-1 cells associated with an electrode poised at -0.4 V. Our results indicate that these electrode potential-responsive promoters enable efficient regulation of gene expression in EAB, providing a molecular basis for the development of electrogenetics.

Use of Microbial Fuel Cells for the Treatment of Residue Effluents Discharged from an Anaerobic Digester Treating Food Wastes.

One of practical challenges in anaerobic-digestion (AD) technology is the cost-effective treatment of residue effluents containing high concentrations of organics, nitrogen and phosphorus (CNP). In order to evaluate the utility of microbial fuel cells (MFCs) for treating anaerobic-digester effluents (ADEs) and generating power from them, laboratory-scale single-chamber MFCs were filled with ADE obtained from a commercial AD plant treating food wastes and thereafter operated by routinely supplying ADE at different hydraulic residence times (HRTs, 5 to 20 days). It is shown that MFCs were able to reduce not only organics in ADE but also nitrogen and phosphorus. For instance, data demonstrated that over 50% of CNP was removed in MFCs operated at an HRT of 10 days, at which the maximum power density reached over 200 mW m-2 (based on the projected area of anode). Metabarcoding of 16S rRNA genes showed that some bacteria were specifically enriched in anode biofilms, suggesting their involvement in power generation. Our study suggests that MFCs are applicable to reducing CNP in ADEs at reasonable rates, and provides subsequent work with fundamental data useful for setting targets for further developments.

Periodontal therapy for localized severe periodontitis in a patient receiving fixed orthodontic treatment: a case report.

BACKGROUND: Orthodontic treatment involves movement of teeth by compression and resorption of the alveolar bone using orthodontic forces. These movements are closely linked to the interactions between the teeth and the periodontal tissues that support them. Owing to an increase in adults seeking orthodontic treatment, orthodontists increasingly encounter patients with periodontal diseases, in whom orthodontic treatment is contraindicated. In rare cases, periodontitis may develop after treatment initiation. However, no approach for treating periodontitis after the initiation of orthodontic treatment has been established. Here, we present an approach for managing localized severe periodontitis manifesting after initiating orthodontic treatment. CASE PRESENTATION: A 32-year-old Japanese woman was referred to the Department of Dentistry and Oral Surgery by an orthodontist who observed symptoms of acute periodontitis in the maxillary molars that required periodontal examination and treatment. A detailed periodontal examination, including oral bacteriological examination, revealed localized severe periodontitis (stage III, grade B) in the maxillary left first and second molars and in the mandibular right second molar. After consultation with the orthodontist, the orthodontic treatment was suspended based on the results of the bacteriological examination to allow for periodontal treatment. Full-mouth disinfection was performed with adjunctive oral sitafloxacin. Periodontal and bacteriological examinations after treatment revealed regression of the localized periodontitis with bone regeneration. Thereafter, orthodontic treatment was resumed, and good progress was achieved. CONCLUSIONS: Orthodontists should recognize the risk of acute severe periodontitis in young adults. Asymptomatic patients with localized severe periodontitis may clear a screening test before orthodontic treatment but develop acute symptoms with bone resorption during orthodontic treatment. Therefore, patients requiring orthodontic treatment should be examined by their family dentist or a periodontist to rule out periodontal issues that may impede orthodontic treatment. The patients should also be informed of age-related risks. Further, periodontists, family dentists, and orthodontists who treat adults should be informed about periodontitis and the need for interdisciplinary collaboration. In patients who develop periodontitis after orthodontic treatment initiation, temporary interruption of orthodontic treatment and aggressive periodontal intervention may facilitate recovery.

A survey of physical and occupational therapists' views on lumbar loading movements.

[Purpose] To identify the lumbar loading movements necessary in clinical practice. [Participants and Methods] A questionnaire survey was conducted among physical and occupational therapists in Japan. There were no exclusion criteria regarding the number of years of experience, age, or field of employment. The participants were randomly selected and administered the questionnaire. They were asked to list and rank the lumbar loadings they considered necessary. [Results] A total of 739 respondents participated in the survey. The results of this nationwide survey indicated that the lifting movement of heavy objects in the trunk flexion position was the most common movement (for 354 participants). [Conclusion] The main loading movements of the lumbar spine were reported to be heavy lifting movements (in the trunk flexion position) and trunk rotation movements. As perspectives, we aim to conduct an analytical study of some of lumbar spine loading movements outlined in this study, using a musculoskeletal simulator and electromyography.

Proton Configuration in Water Chain on Pt(533).

In this paper, a wetting behavior of Pt(533) is studied by using heterodyne-detected vibrational sum-frequency generation spectroscopy under an ultrahigh-vacuum condition at 145 K. The imaginary parts of the surface nonlinear susceptibility (Imχ(2)) of the H-bonded OH stretching region are successfully obtained for submonolayer water coverage that show negative bands indicating H-down (proton pointing to the substrate) configurations both for the water at the step and at the terrace. The growth manner of the Imχ(2) signal with coverage and the results of an isotopic dilution are consistent with a model in which a one-dimensional (1D) chain at the step forms a "zigzag" structure that contains H-down orientations. This finding resolves the previous controversy in the literature concerning the proton configuration in the 1D water chain at the step.

Conformational changes in the catalytic region are responsible for heat-induced activation of hyperthermophilic homoserine dehydrogenase.

When overexpressed as an immature enzyme in the mesophilic bacterium Escherichia coli, recombinant homoserine dehydrogenase from the hyperthermophilic archaeon Sulfurisphaera tokodaii (StHSD) was markedly activated by heat treatment. Both the apo- and holo-forms of the immature enzyme were successively crystallized, and the two structures were determined. Comparison among the structures of the immature enzyme and previously reported structures of mature enzymes revealed that a conformational change in a flexible part (residues 160-190) of the enzyme, which encloses substrates within the substrate-binding pocket, is smaller in the immature enzyme. The immature enzyme, but not the mature enzyme, formed a complex that included NADP+, despite its absence during crystallization. This indicates that the opening to the substrate-binding pocket in the immature enzyme is not sufficient for substrate-binding, efficient catalytic turnover or release of NADP+. Thus, specific conformational changes within the catalytic region appear to be responsible for heat-induced activation.

Development of a CRISPR interference system for selective gene knockdown in Acidithiobacillus ferrooxidans.

Acidithiobacillus ferrooxidans is an iron-oxidizing chemolithotroph used for bioleaching of precious metals and is also regarded as a potential host for bioelectrochemical production of value-added chemicals. Despite its industrial utility, however, it is difficult to genetically engineer A. ferrooxidans due to low transformation and recombination efficiencies. Here, we developed a clustered regularly interspaced short palindromic repeats interference (CRISPRi) system that can selectively repress the expression of a target gene in A. ferrooxidans. The mutated gene encoding a nuclease-deactivated Cas9 protein was cloned into the broad-host-range plasmid pBBR1-MCS2, and the applicability of the CRISPRi system was examined using the nitrogenase nifH gene as a knockdown target. Introduction of the CRISPRi plasmid into A. ferrooxidans resulted in decreased nifH transcription and retarded cell growth in the absence of nitrogen sources, demonstrating that the CRISPRi system altered the phenotype of this bacterium via selective gene knockdown. We suggest that the CRISPRi system developed in this study provides an efficient technique for constructing A. ferrooxidans knockdown mutants that are useful for the genetic dissection of this bacterium.

Proposed protocol for treatment of severe periodontitis without platelet transfusion in patients with aplastic anemia: a case report.

BACKGROUND: Aplastic anemia is an intractable disease characterized by pancytopenia, susceptibility to infection, and difficulty in achieving hemostasis. In patients with severe periodontal disease and aplastic anemia, spontaneous bleeding from the gingival tissue due to thrombocytopenia and during brushing is common, which may further exacerbate dental issues. Comprehensive periodontal treatment for patients with aplastic anemia is highly challenging and requires collaboration with a hematologist. Here, we discuss the case of a patient with aplastic anemia and severe periodontitis who was successfully treated in collaboration with our hematology department. CASE PRESENTATION: A 36-year-old Japanese woman with chief complaints of spontaneous gingival bleeding, pain, and increasing tooth mobility consulted our department. She had developed pancytopenia at age 11 years and was later diagnosed with aplastic anemia, making her susceptible to infection due to leukopenia. The results of the initial periodontal examination led to a diagnosis of severe generalized periodontitis (generalized stage IV grade C periodontitis) caused by leukopenia and poor oral hygiene. We adopted a comprehensive treatment plan, including invasive dental procedures. The patient exhibited no postoperative bleeding due to aplastic anemia-induced thrombocytopenia and experienced a good outcome. CONCLUSIONS: Both physicians and dentists should be aware that immunocompromised patients with aplastic anemia are at risk of developing severe periodontitis with severe alveolar bone resorption if the condition is combined with poor oral hygiene. Even in the presence of aplastic anemia, patients with severe periodontitis can undergo comprehensive dental treatment, including dental extraction and periodontal surgery, if bleeding and susceptibility to infection are controlled. This requires the cooperation of the patient and hematologists and can ultimately contribute to improving the patient's quality of life.

Codh/Acs-Deficient Methanogens Are Prevalent in Anaerobic Digesters.

Methanogens are archaea that grow by producing methane as a catabolic end product and thrive in diverse anaerobic habitats, including soil, sediments, oil reservoirs, digestive tracts, and anaerobic digesters. Methanogens have typically been classified into three types-namely, hydrogenotrophic, acetoclastic, and methylotrophic methanogens. In addition, studies have found methanogens that require both hydrogen/CO2 and organics, such as acetate, for growth. Genomic analyses have shown that these methanogens lack genes for carbon monoxide dehydrogenase/acetyl-CoA synthase (Codh/Acs), one of the oldest enzymes that catalyzes the central step in the Wood-Ljungdahl pathway. Since these methanogens have been found dominant in such habitats as digestive tracts and anaerobic digesters, it is suggested that the loss of Codh/Acs confers ecological advantages on methanogens in these habitats. Comparisons in genomes of methanogens suggest the possibility that these methanogens have emerged recently in anaerobic digesters and are currently under the process of prevalence. We propose that an understanding of the genetic and ecological processes associated with the emergence and prevalence of these methanogens in anaerobic digesters would offer novel evolutionary insights into microbial ecology.

Clinical Characteristics of Predominantly Unilateral Oral Cenesthopathy With and Without Neurovascular Contact.

Oral cenesthopathy (OC) is characterized by unusual oral discomfort without corresponding evidence, and it has often been categorized as "delusional disorder, somatic type". Regarding possible causative factors of OC, involvement of neurovascular contact (NVC) of the trigeminal nerve, which transmits not only pain but also thermal, tactile, and pressure sensations, has never been observed yet. This study aimed to investigate the relationship between clinical characteristics of unilateral OC and the presence of trigeminal nerve NVC. This is a retrospective comparative study that involved 48 patients having predominantly unilateral OC who visited the Psychosomatic Dentistry Clinic of Tokyo Medical and Dental University between April 2016 and February 2019. Magnetic resonance imaging was performed to assess NVC presence. The Oral Dysesthesia Rating Scale (Oral DRS) was used to assess the various oral sensations and functional impairments besides psychometric questionnaires. Clinical characteristics were retrospectively obtained from the patients' medical charts. NVC was present in 45.8% (22/48) of the patients. There was no significant difference in sex, age, psychiatric history, oral psychosomatic comorbidity, and psychometric questionnaire scores between patients with and without NVC. However, compared to the patients with NVC, the patients without NVC had significantly higher scores for overall subjective severity of OC symptoms (p = 0.008). Moreover, patients having predominantly unilateral OC without NVC showed significantly higher scores in symptom severity and functional impairment of the following parameters: movement (p = 0.030), work (p = 0.004), and social activities (p = 0.010). In addition, compared with the patients with NVC, the patients without NVC showed significantly higher averages of the total symptom severity scale (SSS) and functional impairment scale (FIS) scores in the Oral DRS (p = 0.015 and p = 0.031, respectively). Furthermore, compared with the patients with NVC, the patients without NVC had significantly higher numbers of corresponding symptoms in both the SSS and FIS (p = 0.041 and p = 0.007, respectively). While NVC may be involved in the indescribable subtle OC symptoms, more complex mechanisms may also exist in OC patients without NVC, which yield varying and more unbearable oral symptoms.

Spectral Diffusion of Excitons in 3,4,9,10-Perylenetetracarboxylic-diimide (PTCDI) Thin Films.

In this work, we study spectral diffusion of molecular excitons in thin films of 3,4,9,10-perylenetetracarboxylic-diimide by using two-dimensional electronic spectroscopy (2DES). Temperature dependence of the spectral diffusion is studied from 105 to 471 K by analyzing the center line slope (CLS) of the ground-state bleach in the 2DES signal. A significant acceleration of the decay of the CLS with increasing the temperature is observed, which cannot be explained by a linear system-bath coupling model with a harmonic bath. We propose an anharmonic coupling model as the underlying mechanism, in which the exciton energy gap fluctuations by a high-frequency intramolecular vibration are enhanced by coupling with a low-frequency phonon mode.

Shewanella oneidensis MR-1 as a bacterial platform for electro-biotechnology.

The genus Shewanella comprises over 70 species of heterotrophic bacteria with versatile respiratory capacities. Some of these bacteria are known to be pathogens of fishes and animals, while many are non-pathogens considered to play important roles in the global carbon cycle. A representative strain is Shewanella oneidensis MR-1 that has been intensively studied for its ability to respire diverse electron acceptors, such as oxygen, nitrate, sulfur compounds, metals, and organics. In addition, studies have been focused on its ability as an electrochemically active bacterium that is capable of discharging electrons to and receiving electrons from electrodes in bioelectrochemical systems (BESs) for balancing intracellular redox states. This ability is expected to be applied to electro-fermentation (EF) for producing value-added chemicals that conventional fermentation technologies are difficult to produce efficiently. Researchers are also attempting to utilize its electrochemical ability for controlling gene expression, for which electro-genetics (EG) has been coined. Here we review fundamental knowledge on this bacterium and discuss future directions of studies on its applications to electro-biotechnology (EB).

Identification of a Diguanylate Cyclase That Facilitates Biofilm Formation on Electrodes by Shewanella oneidensis MR-1.

In many bacteria, cyclic diguanosine monophosphate (c-di-GMP), synthesized by diguanylate cyclase (DGC), serves as a second messenger involved in the regulation of biofilm formation. Although studies have suggested that c-di-GMP also regulates the formation of electrochemically active biofilms (EABFs) by Shewanella oneidensis MR-1, DGCs involved in this process remained to be identified. Here, we report that the SO_1646 gene, hereafter named dgcS, is upregulated under medium flow conditions in electrochemical flow cells (EFCs), and its product (DgcS) functions as a major DGC in MR-1. In vitro assays demonstrated that purified DgcS catalyzed the synthesis of c-di-GMP from GTP. Comparisons of intracellular c-di-GMP levels in the wild-type strain and a dgcS deletion mutant (ΔdgcS mutant) showed that production of c-di-GMP was markedly reduced in the ΔdgcS mutant when cells were grown in batch cultures and on electrodes in EFCs. Cultivation of the ΔdgcS mutant in EFCs also revealed that the loss of DgcS resulted in impaired biofilm formation and decreased current generation. These findings demonstrate that MR-1 uses DgcS to synthesize c-di-GMP under medium flow conditions, thereby activating biofilm formation on electrodes.IMPORTANCE Bioelectrochemical systems (BESs) have attracted wide attention owing to their utility in sustainable biotechnology processes, such as microbial fuel cells and electrofermentation systems. In BESs, electrochemically active bacteria (EAB) form biofilms on electrode surfaces, thereby serving as effective catalysts for the interconversion between chemical and electric energy. It is therefore important to understand mechanisms for the formation of biofilm by EAB grown on electrodes. Here, we show that a model EAB, S. oneidensis MR-1, expresses DgcS as a major DGC, thereby activating the formation of biofilms on electrodes via c-di-GMP-dependent signal transduction cascades. The findings presented herein provide the molecular basis for improving electrochemical interactions between EAB and electrodes in BESs. The results also offer molecular insights into how Shewanella regulates biofilm formation on solid surfaces in the natural environment.

Towards Application of Electro-Fermentation for the Production of Value-Added Chemicals From Biomass Feedstocks.

According to recent social demands for sustainable developments, the value of biomass as feedstocks for chemical industry is increasing. With the aid of metabolic engineering and genome editing, microbial fermentation has been developed for producing value-added chemicals from biomass feedstocks, while further improvements are desired for producing more diverse chemicals and increasing the production efficiency. The major intrinsic limitation in conventional fermentation technologies is associated with the need for balancing the net redox equivalents between substrates and products, resulting in limited repertories of fermentation products. One solution for this limitation would be "electro-fermentation (EF)" that utilizes bioelectrochemical systems for modifying the intracellular redox state of electrochemically active bacteria, thereby overcoming the redox constraint of fermentation. Recent studies have attempted the production of chemicals based on the concept of EF, while its utility has not been sufficiently demonstrated in terms of low production efficiencies. Here we discuss EF in terms of its concept, current status and future directions, which help us develop its practical applications to sustainable chemical industries.