Research activity information

• Jun. 2023 Metabolomics 2023, Metabolomics Society Early-Career Award（Travel Award）

  共同研究・競争的資金等の業績IDIRI

• CRISPR-Cas9 engineered Saccharomyces cerevisiae for endolysin delivery to combat Listeria monocytogenes.

  David Sáez Moreno, Joana Cunha, Luís Daniel Rodrigues de Melo, Kenya Tanaka, Takahiro Bamba, Tomosiha Hasunuma, Joana Azeredo, Lucília Domingues

  Listeriosis is an infection caused by the consumption of food contaminated with Listeria monocytogenes. It leads to febrile gastroenteritis, central nervous system infections, and even death in risk populations. Bacteriophage endolysins selectively kill bacteria hydrolyzing their cell walls and have emerged as a potential tool for listeriosis control. Ply511 is an anti-Listeria endolysin that has activity against all serovars of L. monocytogenes. The yeast Saccharomyces cerevisiae has been used to produce endolysins for biocontrol, but prior efforts relied on plasmids, which can lead to gene loss and include selection markers unsuitable for therapeutic use. Integration of endolysins in its genome has also been previously demonstrated, relying however, on selection markers for selection and maintenance of the modifications. This study explores S. cerevisiae as a generally regarded as safe (GRAS) platform for producing and displaying Ply511 through CRISPR-Cas9 integration, offering a marker-free and stable solution for Listeria biocontrol. Our results demonstrate that the surface display of Ply511 does not lead to bacterial reduction. In contrast, we show that yeast secreting endolysin significantly reduces L. monocytogenes in cells, supernatants, and cell extracts. The strongest effect was observed with concentrated spent supernatant and cell extract, which reduced L. monocytogenes below the lower limit of quantification. Additionally, the spent supernatant exhibited active anti-Listeria activity in milk. This study highlights yeast-secreted endolysins as a promising platform for listeriosis control and demonstrates the yeast secretion of endolysins can be used for the biocontrol of pathogenic bacteria. KEY POINTS: • S. cerevisiae was edited using CRISPR-Cas9 to display or secrete endolysin Ply511. • Cells, supernatants, and extracts of yeast secreting Ply511 act against L. monocytogenes. • Demonstrates the yeast-based delivery of endolysins to control L. monocytogenes.

  Apr. 2025, Applied microbiology and biotechnology, 109(1) (1), 81 - 81, English, International magazine

  Scientific journal


• Metabolic engineering and cultivation strategies for efficient production of fucoxanthin and related carotenoids.

  Kenya Tanaka, John Chi-Wei Lan, Akihiko Kondo, Tomohisa Hasunuma

  Fucoxanthin, a bioactive carotenoid derived from algae, has attracted considerable attention for its applications in health, cosmetics, and nutrition. Advances in metabolic engineering, such as the overexpression of pathway-specific enzymes and enhancement of precursor availability, have shown promising results in improving production efficiency. However, despite its high value, the biosynthetic pathway of fucoxanthin remains only partially elucidated, posing significant challenges for metabolic engineering efforts. Recent studies have identified previously unknown enzymes and regulatory elements within the pathway, providing opportunities for further productivity enhancements through targeted metabolic modifications. Additionally, adaptive evolution, mutagenesis-driven strain development, and optimized cultivation conditions have demonstrated significant potential to boost fucoxanthin yields. This review consolidates the latest insights into the biosynthetic pathway of fucoxanthin and highlights metabolic engineering strategies aimed at enhancing the production of fucoxanthin and related carotenoids, offering approaches to design high-yielding strains. Furthermore, recent advancements in random mutagenesis and cultivation technology are discussed. By integrating these developments, more economically viable and environmentally sustainable fucoxanthin production systems can be achieved. KEY POINTS : • Insights into fucoxanthin biosynthesis enable targeted metabolic engineering. • ALE and cultivation strategies complement metabolic engineering efforts. • Balanced push-pull-block strategies improve fucoxanthin production efficiency.

  Lead, Mar. 2025, Applied microbiology and biotechnology, 109(1) (1), 57 - 57, English, International magazine

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• EngineeringSaccharomyces cerevisiaefor growth on xylose using an oxidative pathway

  Kenya Tanaka, Takahiro Yukawa, Takahiro Bamba, Miho Wakiya, Ryota Kumokita, Jin Yong-Su, Akihiko Kondo, Tomohisa Hasunuma

  Lead, Dec. 2024, Applied Microbiology and Biotechnology

  Scientific journal


• Minimized dark consumption of Calvin cycle intermediates facilitates the initiation of photosynthesis in Synechocystis sp. PCC 6803.

  Kenya Tanaka, Akihiko Kondo, Tomohisa Hasunuma

  Cyanobacteria intricately regulate their metabolic pathways during the diurnal cycle to ensure survival and growth. Under dark conditions, the breakdown of glycogen, an energy reserve, in these organisms replenishes Calvin cycle intermediates, especially downstream glycolytic metabolites, which are necessary for photosynthesis initiation upon light irradiation. However, it remains unclear how the accumulation of these intermediates is maintained in the dark despite limited glycogen availability. Therefore, in this study, we investigated the regulation of downstream glycolytic metabolites of the Calvin cycle under dark and light treatment using Synechocystis sp. PCC 6803. Our results showed that during the dark period, low pyruvate kinase (Pyk) activity ensured metabolite accumulation, while endogenous Pyk overexpression significantly lowered the accumulation of glycolytic intermediates. Remarkably, wild type Synechocystis maintained oxygen evolution ability throughout dark treatment for over 2 d, while Pyk overexpression resulted in decreased oxygen evolution after 16 h of dark treatment. These results indicated that limiting Pyk activity via darkness treatment facilitates photosynthetic initiation by maintaining glycolytic intermediates. Similarly, phosphoenolpyruvate carboxylase (PepC) overexpression decreased oxygen evolution under dark treatment; however, its effect was lower than that of Pyk. Further, we noted that as PepC overexpression decreased the levels of glycolytic intermediates in the dark, sugar phosphates in the Calvin-Benson-Bassham (CBB) cycle showed high accumulation, suggesting that sugar phosphates play important roles in supporting photosynthesis initiation. Therefore, our study highlights the importance of controlling the metabolic pathways through which glycolytic and CBB cycle intermediates are consumed (defined as cataplerosis of CBB cycle) to ensure stable photosynthesis.

  Sep. 2024, Plant & cell physiology, English, Domestic magazine

  Scientific journal


• Electrochemical Monitoring of Metabolic Activity of Methane/Methanol Conversing Methylococcus Capsulatus (Bath) Cells Based on Extracellular Electron Transfer

  SUGIMOTO Kugako, HORI Katsutoshi, ISHIKAWA Masahito, ITO Hidehiro, KAMACHI Toshiaki, TANAKA Kenya, CHEN Yan-Yu, NAKANISHI Shuji

  Bioconversion of methane to methanol by methanotrophs under mild conditions is a promising approach for efficiently utilizing methane. Here, we present an electrochemical technique based on open-circuit potential (OCP) measurements to monitor the metabolic activity of Methylococcus capsulatus (Bath), a representative methanotrophic model. This technique is based on the extracellular electron transfer (EET) mechanism, in which intracellular electrons in living cells are exchanged across the cell membrane with an extracellular electrode. Without using artificial electron mediators in our study, we observed that OCP shifted to negative when methane metabolism was activated. By manipulating the culture conditions with the absence or presence of copper supplement to regulate the expression of outer membrane cytochromes (OMCs), the cells with a high OMC expression level, known to serve as conduits for EET, responded with increased sensitivity to stimulation with excess NADH compared to the cells with a low OMC expression level. We, therefore, used the instinctive EET capacity of M. capsulatus (Bath) for real-time OCP measurement to monitor the bioconversion of methane to methanol. Our measurements showed that the OCP levels change with intracellular redox variations and reflect methanol production rates. Our findings may facilitate the development of a methanotrophic bioprocess that allows more effective and efficient control of intracellular redox status using OCP monitoring based on EET.

  The Electrochemical Society of Japan, Feb. 2024, Electrochemistry, 92(2) (2), 022007 - 022007, English


• Metabolomics-based development of bioproduction processes toward industrial-scale production.

  Kenya Tanaka, Takahiro Bamba, Akihiko Kondo, Tomohisa Hasunuma

  Microbial biomanufacturing offers a promising, environment-friendly platform for next-generation chemical production. However, its limited industrial implementation is attributed to the slow production rates of target compounds and the time-intensive engineering of high-yield strains. This review highlights how metabolomics expedites bioproduction development, as demonstrated through case studies of its integration into microbial strain engineering, culture optimization, and model construction. The Design-Build-Test-Learn (DBTL) cycle serves as a standard workflow for strain engineering. Process development, including the optimization of culture conditions and scale-up, is crucial for industrial production. In silico models facilitate the development of strains and processes. Metabolomics is a powerful driver of the DBTL framework, process development, and model construction.

  Lead, Dec. 2023, Current opinion in biotechnology, 85, 103057 - 103057, English, International magazine

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Recent research advances on non-linear phenomena in various biosystems

  Yutaka Tamaru, Shuji Nakanishi, Kenya Tanaka, Mitsuo Umetsu, Hikaru Nakazawa, Aruto Sugiyama, Tomoyuki Ito, Naofumi Shimokawa, Masahiro Takagi

  Elsevier BV, Aug. 2023, Journal of Bioscience and Bioengineering, 136(2) (2), 75 - 86

  Scientific journal


• Dark accumulation of downstream glycolytic intermediates initiates robust photosynthesis in cyanobacteria

  Kenya Tanaka, Tomokazu Shirai, Christopher J Vavricka, Mami Matsuda, Akihiko Kondo, Tomohisa Hasunuma

  Abstract Photosynthesis must maintain stability and robustness throughout fluctuating natural environments. In cyanobacteria, dark-to-light transition leads to drastic metabolic changes from dark respiratory metabolism to CO2 fixation through the Calvin–Benson–Bassham (CBB) cycle using energy and redox equivalents provided by photosynthetic electron transfer. Previous studies have shown that catabolic metabolism supports the smooth transition into CBB cycle metabolism. However, metabolic mechanisms for robust initiation of photosynthesis are poorly understood due to lack of dynamic metabolic characterizations of dark-to-light transitions. Here, we show rapid dynamic changes (on a time scale of seconds) in absolute metabolite concentrations and 13C tracer incorporation after strong or weak light irradiation in the cyanobacterium Synechocystis sp. PCC 6803. Integration of this data enabled estimation of time-resolved nonstationary metabolic flux underlying CBB cycle activation. This dynamic metabolic analysis indicated that downstream glycolytic intermediates, including phosphoglycerate and phosphoenolpyruvate, accumulate under dark conditions as major substrates for initial CO2 fixation. Compared with wild-type Synechocystis, significant decreases in the initial oxygen evolution rate were observed in 12 h dark preincubated mutants deficient in glycogen degradation or oxidative pentose phosphate pathways. Accordingly, the degree of decrease in the initial oxygen evolution rate was proportional to the accumulated pool size of glycolytic intermediates. These observations indicate that the accumulation of glycolytic intermediates is essential for efficient metabolism switching under fluctuating light environments.

  Lead, Oxford University Press (OUP), Dec. 2022, Plant Physiology

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Order-of-magnitude enhancement in photocurrent generation of Synechocystis sp. PCC 6803 by outer membrane deprivation

  Shoko Kusama, Seiji Kojima, Ken Kimura, Ginga Shimakawa, Chikahiro Miyake, Kenya Tanaka, Yasuaki Okumura, Shuji Nakanishi

  Abstract Biophotovoltaics (BPV) generates electricity from reducing equivalent(s) produced by photosynthetic organisms by exploiting a phenomenon called extracellular electron transfer (EET), where reducing equivalent(s) is transferred to external electron acceptors. Although cyanobacteria have been extensively studied for BPV because of their high photosynthetic activity and ease of handling, their low EET activity poses a limitation. Here, we show an order-of-magnitude enhancement in photocurrent generation of the cyanobacterium Synechocystis sp. PCC 6803 by deprivation of the outer membrane, where electrons are suggested to stem from pathway(s) downstream of photosystem I. A marked enhancement of EET activity itself is verified by rapid reduction of exogenous electron acceptor, ferricyanide. The extracellular organic substances, including reducing equivalent(s), produced by this cyanobacterium serve as respiratory substrates for other heterotrophic bacteria. These findings demonstrate that the outer membrane is a barrier that limits EET. Therefore, depriving this membrane is an effective approach to exploit the cyanobacterial reducing equivalent(s).

  Springer Science and Business Media LLC, Dec. 2022, Nature Communications, 13(1) (1)

  Scientific journal


• NADPH production in dark stages is critical for cyanobacterial photocurrent generation: a study using mutants deficient in oxidative pentose phosphate pathway

  Jiro Hatano, Shoko Kusama, Kenya Tanaka, Ayaka Kohara, Chikahiro Miyake, Shuji Nakanishi, Ginga Shimakawa

  Live cyanobacteria and algae integrated onto an extracellular electrode can generate a light-induced current (i.e., a photocurrent). Although the photocurrent is expected to be correlated with the redox environment of the photosynthetic cells, the relationship between the photocurrent and the cellular redox state is poorly understood. Here, we investigated the effect of the reduced nicotinamide adenine dinucleotide phosphate [NADP(H)] redox level of cyanobacterial cells (before light exposure) on the photocurrent using several mutants (Δzwf, Δgnd, and ΔglgP) deficient in the oxidative pentose phosphate (OPP) pathway, which is the metabolic pathway that produces NADPH in darkness. The NAD(P)H redox level and photocurrent in the cyanobacterium Synechocystis sp. PCC 6803 were measured noninvasively. Dysfunction of the OPP pathway led to oxidation of the photosynthetic NADPH pool in darkness. In addition, photocurrent induction was retarded and the current density was lower in Δzwf, Δgnd, and ΔglgP than in wild-type cells. Exogenously added glucose compensated the phenotype of ΔglgP and drove the OPP pathway in the mutant, resulting in an increase in the photocurrent. The results indicated that NADPH accumulated by the OPP pathway before illumination is a key factor for the generation of a photocurrent. In addition, measuring the photocurrent can be a non-invasive approach to estimate the cellular redox level related to NADP(H) pool in cyanobacteria.

  Feb. 2022, Photosynthesis Research, 153(1-2) (1-2), 113 - 120, English, International magazine

  Scientific journal


• Conserved Two-component Hik2–Rre1 Signaling Is Activated Under Temperature Upshift and Plastoquinone-reducing Conditions in the Cyanobacterium Synechococcus elongatus PCC 7942

  Nachiketa Bairagi, Satoru Watanabe, Kaori Nimura-Matsune, Kenya Tanaka, Tatsuhiro Tsurumaki, Shuji Nakanishi, Kan Tanaka

  Abstract The highly conserved Hik2–Rre1 two-component system is a multi-stress responsive signal-transducing module that controls the expression of hsp and other genes in cyanobacteria. Previously, we found in Synechococcus elongatus PCC 7942 that the heat-inducible phosphorylation of Rre1 was alleviated in a hik34 mutant, suggesting that Hik34 positively regulates signaling. In this study, we examined the growth of the hik34 deletion mutant in detail, and newly identified suppressor mutations located in rre1 or sasA gene negating the phenotype. Subsequent analyses indicated that heat-inducible Rre1 phosphorylation is dependent on Hik2 and that Hik34 modulates this Hik2-dependent response. In the following part of this study, we focused on the mechanism to control the Hik2 activity. Other recent studies reported that Hik2 activity is regulated by the redox status of plastoquinone (PQ) through the 3Fe-4S cluster attached to the cyclic GMP, adenylyl cyclase, FhlA (GAF) domain. Consistent with this, Rre1 phosphorylation occurred after the addition of 2,5-dibromo-6-isopropyl-3-methyl-1,4-benzoquinone but not after the addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea to the culture medium, which corresponded to PQ-reducing or -oxidizing conditions, respectively, suggesting that the Hik2-to-Rre1 phosphotransfer was activated under PQ-reducing conditions. However, there was no correlation between the measured PQ redox status and Rre1 phosphorylation during the temperature upshift. Therefore, changes in the PQ redox status are not the direct reason for the heat-inducible Rre1 phosphorylation, while some redox regulation is likely involved as oxidation events dependent on 2,6-dichloro-1,4-benzoquinone prevented heat-inducible Rre1 phosphorylation. On the basis of these results, we propose a model for the control of Hik2-dependent Rre1 phosphorylation.

  Oxford University Press (OUP), Feb. 2022, Plant and Cell Physiology, 63(2) (2), 176 - 188

  Scientific journal


• Coral symbionts evolved a functional polycistronic flavodiiron gene

  Ginga Shimakawa, Eiichi Shoguchi, Adrien Burlacot, Kentaro Ifuku, Yufen Che, Minoru Kumazawa, Kenya Tanaka, Shuji Nakanishi

  Photosynthesis in cyanobacteria, green algae, and basal land plants is protected against excess reducing pressure on the photosynthetic chain by flavodiiron proteins (FLV) that dissipate photosynthetic electrons by reducing O2. In these organisms, the genes encoding FLV are always conserved in the form of a pair of two-type isozymes (FLVA and FLVB) that are believed to function in O2 photo-reduction as a heterodimer. While coral symbionts (dinoflagellates of the family Symbiodiniaceae) are the only algae to harbor FLV in photosynthetic red plastid lineage, only one gene is found in transcriptomes and its role and activity remain unknown. Here, we characterized the FLV genes in Symbiodiniaceae and found that its coding region is composed of tandemly repeated FLV sequences. By measuring the O2-dependent electron flow and P700 oxidation, we suggest that this atypical FLV is active in vivo. Based on the amino-acid sequence alignment and the phylogenetic analysis, we conclude that in coral symbionts, the gene pair for FLVA and FLVB have been fused to construct one coding region for a hybrid enzyme, which presumably occurred when or after both genes were inherited from basal green algae to the dinoflagellate. Immunodetection suggested the FLV polypeptide to be cleaved by a post-translational mechanism, adding it to the rare cases of polycistronic genes in eukaryotes. Our results demonstrate that FLV are active in coral symbionts with genomic arrangement that is unique to these species. The implication of these unique features on their symbiotic living environment is discussed.

  Springer Science and Business Media {LLC}, Jan. 2022, Photosynthesis Research, 151(1) (1), 113 - 124, English, International magazine

  Scientific journal


• Quantification of NAD(P)H in cyanobacterial cells by a phenol extraction method

  Kenya Tanaka, Ginga Shimakawa, Hiro Tabata, Shoko Kusama, Chikahiro Miyake, Shuji Nakanishi

  Abstract In photosynthetic organisms, it is recognized that the intracellular redox ratio of NADPH is regulated within an appropriate range for the cooperative function of a wide variety of physiological processes. However, despite its importance, there is large variability in the values of the NADPH fraction [NADPH/(NADPH + NADP⁺)] quantitatively estimated to date. In the present study, the light response of the NADPH fraction was investigated by applying a novel NADP(H) extraction method using phenol / chloroform / isoamyl alcohol (PCI) in the cyanobacterium Synechocystis sp. PCC 6803. The light response of NADP(H) observed using PCI extraction was qualitatively consistent with the NAD(P)H fluorescence time course measured in vivo. Moreover, the results obtained by PCI extraction and the fluorescence-based methods were also consistent in a mutant lacking the ability to oxidize NAD(P)H in the respiratory chain, and exhibiting a unique NADPH light response. These observations indicate that the PCI extraction method allowed quantitative determination of NADP(H) redox. Notably, the PCI extraction method showed that not all NADP(H) was oxidized or reduced by light–dark transition. Specifically, the fraction of NADPH was 42% in the dark-adapted cell, and saturated at 68% in light conditions.

  Lead, Springer Science and Business Media LLC, May 2021, Photosynthesis Research, 148(1-2) (1-2), 57 - 66, English, International magazine

  Scientific journal


• Ferrihydrite Reduction by Photosynthetic Synechocystis sp. PCC 6803 and Its Correlation With Electricity Generation

  Kenya Tanaka, Ginga Shimakawa, Shoko Kusama, Takashi Harada, Souichiro Kato, Shuji Nakanishi

  Microbial extracellular electron transfer (EET) to solid-state electron acceptors such as anodes and metal oxides, which was originally identified in dissimilatory metal-reducing bacteria, is a key process in microbial electricity generation and the biogeochemical cycling of metals. Although it is now known that photosynthetic microorganisms can also generate (photo)currents via EET, which has attracted much interest in the field of biophotovoltaics, little is known about the reduction of metal (hydr)oxides via photosynthetic microbial EET. The present work quantitatively assessed the reduction of ferrihydrite in conjunction with the EET of the photosynthetic microbe Synechocystis sp. PCC 6803. Microbial reduction of ferrihydrite was found to be initiated in response to light but proceeded at higher rates when exogenous glucose was added, even under dark conditions. These results indicate that current generation from Synechocystis cells does not always need light irradiation. The qualitative trends exhibited by the ferrihydrite reduction rates under various conditions showed significant correlation with those of the microbial currents. Notably, the maximum concentration of Fe(II) generated by the cyanobacterial cells under dark conditions in the presence of glucose was comparable to the levels observed in the photic layers of Fe-rich microbial mats.

  Lead, Frontiers Media SA, Mar. 2021, Frontiers in Microbiology, 12, 650832 - 650832, English, International magazine

  Scientific journal


• Time-of-day-dependent responses of cyanobacterial cellular viability against oxidative stress

  Kenya Tanaka, Ginga Shimakawa, Shuji Nakanishi

  As an adaptation to periodic fluctuations of environmental light, photosynthetic organisms have evolved a circadian clock. Control by the circadian clock of many cellular physiological functions, including antioxidant enzymes, metabolism and the cell cycle, has attracted attention in the context of oxidative stress tolerance. However, since each physiological function works in an integrated manner to deal with oxidative stress, whether or not cell responses to oxidative stress are under circadian control remains an open question. In fact, circadian rhythms of oxidative stress tolerance have not yet been experimentally demonstrated. In the present work, we applied an assay using methyl viologen (MV), which generates reactive oxygen species (ROS) under light irradiation, and experimentally verified the circadian rhythms of oxidative stress tolerance in photosynthetic cells of the cyanobacterium Synechococcus elongatus PCC 7942, a standard model species for investigation of the circadian clock. Here, we report that ROS generated by MV treatment causes damage to stroma components and not to the photosynthetic electron transportation chain, leading to reduced cell viability. The degree of decrease in cell viability was dependent on the subjective time at which oxidative stress was applied. Thus, oxidative stress tolerance was shown to exhibit circadian rhythms. In addition, the rhythmic pattern of oxidative stress tolerance disappeared in mutant cells lacking the essential clock genes. Notably, ROS levels changed periodically, independent of the MV treatment. Thus, we demonstrate for the first time that in cyanobacterial cells, oxidative stress tolerance shows circadian oscillation.

  Lead, Dec. 2020, Scientific Reports, 10(1) (1), 20029 - 20029, English, International magazine

  Scientific journal


• Mediator-Microorganism Interaction in Microbial Solar Cell: a Fluo-Electrochemical Insight

  Léna Beauzamy, Jérôme Delacotte, Benjamin Bailleul, Kenya Tanaka, Shuji Nakanishi, Francis-André Wollman, Frédéric Lemaître

  American Chemical Society (ACS), Jun. 2020, Analytical Chemistry, 92(11) (11), 7532 - 7539

  Scientific journal


• Extracellular electron transfer mediated by a cytocompatible redox polymer to study the crosstalk among the mammalian circadian clock, cellular metabolism, and cellular redox state

  Masahito Ishikawa, Kazuki Kawai, Masahiro Kaneko, Kenya Tanaka, Shuji Nakanishi, Katsutoshi Hori

  Royal Society of Chemistry ({RSC}), 2020, RSC Advances, 10(3) (3), 1648 - 1657

  Scientific journal


• The endogenous redox rhythm is controlled by a central circadian oscillator in cyanobacterium Synechococcus elongatus PCC7942

  Kenya Tanaka, Masahito Ishikawa, Masahiro Kaneko, Kazuhide Kamiya, Souichiro Kato, Shuji Nakanishi

  Lead, Springer Science and Business Media {LLC}, Nov. 2019, Photosynthesis Research, 142(2) (2), 203 - 210

  Scientific journal


• Extracellular Electron Transfer via Outer Membrane Cytochromes in a Methanotrophic Bacterium Methylococcus capsulatus (Bath)

  Kenya Tanaka, Sho Yokoe, Kensuke Igarashi, Motoko Takashino, Masahito Ishikawa, Katsutoshi Hori, Shuji Nakanishi, Souichiro Kato

  Electron exchange reactions between microbial cells and solid materials, referred to as extracellular electron transfer (EET), have attracted attention in the fields of microbial physiology, microbial ecology, and biotechnology. Studies of model species of iron-reducing, or equivalently, current-generating bacteria such as Geobacter spp. and Shewanella spp. have revealed that redox-active proteins, especially outer membrane c-type cytochromes (OMCs), play a pivotal role in the EET process. Recent (meta)genomic analyses have revealed that diverse microorganisms that have not been demonstrated to have EET ability also harbor OMC-like proteins, indicating that EET via OMCs could be more widely preserved in microorganisms than originally thought. A methanotrophic bacterium Methylococcus capsulatus (Bath) was reported to harbor multiple OMC genes whose expression is elevated by Cu starvation. However, the physiological role of these genes is unknown. Therefore, in this study, we explored whether M. capsulatus (Bath) displays EET abilities via OMCs. In electrochemical analysis, M. capsulatus (Bath) generated anodic current only when electron donors such as formate were available, and could reduce insoluble iron oxides in the presence of electron donor compounds. Furthermore, the current-generating and iron-reducing activities of M. capsulatus (Bath) cells that were cultured in a Cu-deficient medium, which promotes high levels of OMC expression, were higher than those cultured in a Cu-supplemented medium. Anodic current production by the Cu-deficient cells was significantly suppressed by disruption of MCA0421, a highly expressed OMC gene, and by treatment with carbon monoxide (CO) gas (an inhibitor of c-type cytochromes). Our results provide evidence of EET in M. capsulatus (Bath) and demonstrate the pivotal role of OMCs in this process. This study raises the possibility that EET to solid compounds is a novel survival strategy of methanotrophic bacteria.

  Lead, Frontiers Media SA, Nov. 2018, Frontiers in Microbiology, 9

  Scientific journal


• Specific Interaction between Redox Phospholipid Polymers and Plastoquinone in Photosynthetic Electron Transport Chain

  Tanaka, Kenya, Kaneko, Masahiro, Ishikawa, Masahito, Kato, Souichiro, Ito, Hidehiro, Kamachi, Toshiaki, Kamiya, Kazuhide, Nakanishi, Shuji

  Lead, 2017, Chemphyschem, 18(8) (8)

  Scientific journal


• Real-time monitoring of intracellular redox changes in Methylococcus capsulatus (Bath) for efficient bioconversion of methane to methanol

  Ishikawa, Masahito, Tanaka, Yuya, Suzuki, Risa, Kimura, Kota, Tanaka, Kenya, Kamiya, Kazuhide, Ito, Hidehiro, Kato, Souichiro, Kamachi, Toshiaki, Hori, Katsutoshi, Nakanishi, Shuji

  2017, Bioresource Technology, 241, 1157 - 1161, English

  Scientific journal

• 光合成微生物の代謝ダイナミクス解析—Analyses of metabolic dynamics in photosynthetic microbes

  田中 謙也, 蓮沼 誠久

  東京 : 北隆館, Jul. 2024, アグリバイオ = Agricultural biotechnology, 8(8) (8), 691 - 695, Japanese


• Maintaining downstream glycolytic intermediates ensures rapid start of photosynthesis in cyanobacteria

  田中謙也, 田中謙也, 田中謙也, 松田真実, 白井智量, 白井智量, 近藤昭彦, 近藤昭彦, 近藤昭彦, 蓮沼誠久, 蓮沼誠久, 蓮沼誠久

  2023, 日本植物生理学会年会(Web), 64th


• Metabolism for photosynthetic induction in cyanobacteria

  田中謙也, 蓮沼誠久

  2023, 光合成研究, 33(1) (1)


• A quantitative characterization of metabolic dynamics during photosynthesis start in cyanobacteria

  田中謙也, 田中謙也, 松田真実, 白井智量, 蓮沼誠久, 蓮沼誠久

  2022, 日本植物生理学会年会(Web), 63rd


• Analysis of mechanism of extracellular electron transfer from cyanobacterium Synechocystis sp. PCC 6803

  草間翔子, 田中謙也, 畑野二郎, 河本尚大, 嶋川銀河, 田畑裕, 三宅里佳, 中西周次

  2022, 電気化学会大会講演要旨集(CD-ROM), 89th


• A quantitative characterization of rapid metabolic dynamics during activation of Calvin cycle in cyanobacteria

  田中謙也, 白井智量, 白井智量, 松田真実, 近藤昭彦, 近藤昭彦, 近藤昭彦, 蓮沼誠久, 蓮沼誠久, 蓮沼誠久

  2022, 日本生物工学会大会講演要旨集, 74th


• A quantitative demonstration of the NADP⁺/NADPH redox homeostasis in cyanobacterial cells

  田中謙也, 嶋川銀河, 田畑裕, 草間翔子, 中西周次, 中西周次

  2021, 日本植物生理学会年会(Web), 62nd


• Deprivation of outer membrane enhances extracellular electron transfer activity of cyanobacterium Synechocystis sp. PCC 6803

  草間翔子, 草間翔子, 児島征司, 木村拳, 田中謙也, 嶋川銀河, 奥村泰章, 中西周次, 中西周次

  2021, 日本植物生理学会年会(Web), 62nd


• Highly-accurate quantification of NADP(H) in cyanobacteria

  田中謙也, 田中謙也, 嶋川銀河, 嶋川銀河, 草間翔子, 松田真実, 蓮沼誠久, 蓮沼誠久, 中西周次

  2021, 日本生物工学会大会講演要旨集, 73rd


• Enhancement in photocurrent-generating capacity of cyanobacterium Synechocystis sp. PCC 6803 by deprivation of outer membrane

  草間翔子, 草間翔子, 児島征司, 嶋川銀河, 田中謙也, 奥村泰章, 中西周次

  2021, 電気化学秋季大会講演要旨集(CD-ROM), 2021


• Electrochemical monitoring of intracellular redox state in cyanobacteria

  田中謙也, 石川聖人, 石川聖人, 中西周次, 中西周次

  2020, 光合成研究, 30(1) (1)


• 光合成生物の光環境適応に関わる細胞内レドックス

  田中謙也, 中西周次

  2020, 生物工学会誌, 98(4) (4)


• Cellular oxidative stress tolerance regulated by circadian clock in Synechococcus elongatus PCC7942

  田中謙也, 中西周次, 中西周次

  2020, 日本植物生理学会年会(Web), 61st


• シアノバクテリアSynechococcus elongatus PCC7942における概日時計に制御された酸化ストレス耐性

  田中謙也, 中西周次, 中西周次

  2019, 日本微生物生態学会大会(Web), 33rd


• 酸化ストレス条件下におけるシアノバクテリアの細胞内レドックス状態

  田畑裕, 田中謙也, 中西周次

  2019, 電気化学秋季大会講演要旨集(CD-ROM), 2019


• Oxidative stress tolerance controlled by the circadian clock in cyanobacterium Synechococcus elongatus PCC7942 cells

  田中謙也, 中西周次, 中西周次

  2019, 時間生物学, 25(2) (2)


• シアノバクテリアにおける光不応答性の概日レドックスリズムと抗酸化機能

  田中謙也, 石川聖人, 石川聖人, 田畑裕, 加藤創一郎, 加藤創一郎, 中西周次, 中西周次, 中西周次

  2018, 時間生物学, 24(2) (2)


• 電子伝達高分子を介したレドックス摂動が概日時計に与える影響

  河合和紀, 石川聖人, 石川聖人, 金子真大, 田中謙也, 中西周次, 中西周次, 堀克敏

  2018, 時間生物学, 24(2) (2)


• シアノバクテリア概日時計における循環的レドックスシグナル伝達

  中西周次, 田中謙也, 金子真大, 石川聖人, 石川聖人, 加藤創一郎, 加藤創一郎

  2017, 電気化学会大会講演要旨集(CD-ROM), 84th


• シアノバクテリアの概日時計遺伝子発現と光合成電子伝達系レドックス状態との相関

  中西周次, 石川聖人, PORNPITRA Tunanunkul, 田中謙也, 西脇妙子, 北山陽子, 加藤創一郎, 橋本和仁

  2016, 電気化学会大会講演要旨集(CD-ROM), 83rd

• CO[2]の有効利用技術の開発

  橋﨑, 克雄, 技術情報協会

  技術情報協会, Jul. 2023, Japanese, ISBN: 9784861049729

• Development of a comprehensive analytical method for disulfide redox potentials using redox proteomics

  Kenya Tanaka, Akihiko Kondo, Tomohisa Hasunuma

  第66回日本植物生理学会年会, Mar. 2025


• Development of basic strains in photosynthetic microorganisms for commodity chemical bioproduction

  Kenya Tanaka

  GI forum 2nd workshop, Feb. 2025, Japanese

  [Invited]

  Invited oral presentation


• Function and evolution of metabolism and redox state

  Kenya Tanaka

  CLS seminar, Jan. 2025, Japanese

  [Invited]

  Invited oral presentation


• Analysis of redox and metabolic changes in photosynthetic microorganisms

  Kenya Tanaka

  Asian Synthetic Biology Association 2024, Jan. 2025, English

  [Invited]

  Invited oral presentation


• コモディティケミカル生産光合成微生物の開発 代謝解析技術の紹介

  田中謙也

  バイオものづくり研究者の月例発表会, Oct. 2024


• Development of basic strains in photosynthetic microorganisms toward low carbon bioproduction

  田中謙也, 加藤 悠一, 馬場嵜 樹, 近藤 昭彦, 蓮沼 誠久

  第76回 日本生物工学会, Sep. 2024

  Nominated symposium


• 細胞内レドックス測定～電子の流れの定量的理解をめざして～

  田中謙也

  ACT-X 分科会「酵素・電気化学」, Jul. 2024


• オミクス解析技術をもとにしたバイオものづくり

  田中 謙也

  低温工学関西支部・講演会, May 2024

  [Invited]

  Invited oral presentation


• 代謝・レドックスの観測 ～バイオの不確定性原理！？～

  田中謙也

  微生物代謝研究会, May 2024

  [Invited]

  Invited oral presentation


• Comprehensive analysis of reduction potential of cysteine residues using redox proteomics

  田中謙也, 近藤昭彦, 蓮沼誠久

  第65回 日本植物生理学会年会, Mar. 2024

  Oral presentation


• オミクス解析技術をもとにした光合成物質生産

  田中 謙也

  関西バイオものづくりフォーラム, Mar. 2024

  [Invited]

  Invited oral presentation


• Comprehensive analysis of reduction potential using redox proteomics

  Kenya Tanaka, Akihiko Kondo, Tomohisa Hasunuma

  Asian Synthetic Biology Association 2023, Dec. 2023, English

  Oral presentation


• Dynamic metabolic flux analysis during photosynthesis activation in cyanobacteria

  K. Tanaka, T. Shirai, M. Matsuda, A. Kondo, T. Hasunuma

  Metabolomics 2023, Jun. 2023

  Oral presentation


• 異なる電位環境下でのシアノバクテリアのシステインレドックスプロテオミクス解析

  田中 謙也, 近藤 昭彦, 蓮沼 誠久

  第13回日本光合成学会年会, Jun. 2023

  Poster presentation


• Maintaining downstream glycolytic intermediates ensures rapid start of photosynthesis in cyanobacteria

  Kenya Tanaka, Tomokazu Shirai, Mami Matsuda, Akihiko Kondo, Tomohisa Hasunuma

  第64回日本植物生理学会年会, Mar. 2023

  Oral presentation


• 環境適応型バイオ生産微生物の開発を指向した酸化還元バランス維持機構の研究

  田中謙也

  神戸大学創立120周年記念式典, Dec. 2022

  Others


• Metabolism for robust initiation of photosynthesis in cyanobacteria

  K. Tanaka, T. Shirai, M. Matsuda, A. Kondo, T. Hasunuma

  International Symposium on Photosynthesis and Chloroplast Regulation, Nov. 2022

  Oral presentation


• 絶対定量メタボロミクスによる 光合成活性化時の高速代謝変化の解析

  田中謙也, 松田真実, 白井智量, 近藤昭彦, 蓮沼誠久

  第16回メタボロームシンポジウム, Sep. 2022

  Oral presentation


• シアノバクテリアにおける光合成代謝のin vivo活性化キネティクス

  田中 謙也, 白井 智量, 松田 真実, 近藤 昭彦, 蓮沼 誠久

  第12回光合成学会年会, May 2022


• A quantitative characterization of metabolic dynamics during photosynthesis start in cyanobacteria

  田中謙也, 松田真実, 白井智量, 蓮沼誠久

  第63回 植物生理学会年会, Mar. 2022

  Oral presentation


• A quantitative demonstration of the NADP+/NADPH redox homeostasis in cyanobacterial cells

  田中謙也, 嶋川銀河, 田畑裕, 草間翔子, 中西周次

  第62回日本植物生理学会年会, Mar. 2021


• Electrochemical study on the endogenous redox rhythm in cyanobacterium Synechococcus elongatus PCC7942

  K. Tanaka, S. Nakanishi

  71st Annual Meeting of the International Society of Electrochemistry, Aug. 2020

  Poster presentation


• Loop signal transduction between the circadian clock and intracellular redox in Synechococcus elongatus PCC7942

  K. Tanaka, M. Ishikawa, S. Kato, S. Nakanishi

  16th International Symposium on Phototropic Prokaryotes 2018, Aug. 2018

  Poster presentation

• 日本植物生理学会


• 日本微生物生態学会


• 日本時間生物学会


• 日本生物工学会


• 日本光合成学会

• 海洋一次生産を支える珪藻型炭素同化反応の実体解明

  嶋川 銀河

  日本学術振興会, 科学研究費助成事業, 基盤研究(B), 神戸大学, Apr. 2025 - Mar. 2028, Coinvestigator


• 多様な微生物機能の開拓のためのバイオものづくりDBTL技術の開発

  本田 孝祐

  科学技術振興機構, 大阪大学, 2023 - 2027, Coinvestigator

  日本のバイオものづくりは中規模・多品種型生産で世界をけん引してきた。しかし、一連のプロセス開発研究が個社に委ねられてきたため、プロセス開発期間の長期化と高コスト化、スケールメリットの小ささがボトルネックとなっている。この課題を解決するためには、産業形態の垂直統合型から水平分業型への変革、実プロセスからバックキャストした設計思想に基づく新たな育種技術の開発が必要である。 これらを実現するために本研究では以下の課題に取り組む。 1) プロセス開発の共通言語となる標準的な細胞(ベーシックセル)の作出 2) 汎用微生物にはないユニークな機能を備えた微生物の探索と宿主化 3) Design-Build-Test-Learn (DBTL)サイクルの次世代化 これらの取り組みによりプロセス開発期間の短縮、新規事業者の参入拡大、プロダクトの多様化を加速し、持続的なバイオエコノミー拡大に貢献する。


• 高時間分解・絶対定量代謝解析による光合成代謝変動と酸化還元バランス維持機構の解明

  田中 謙也

  日本学術振興会, 科学研究費助成事業 若手研究, 若手研究, 神戸大学, 01 Apr. 2022 - 31 Mar. 2025


• 褐虫藻-サンゴ共生系における代謝動態と白化現象との相関の体系的理解

  田中 謙也

  日本学術振興会, 科学研究費助成事業 特別研究員奨励費, 特別研究員奨励費, 神戸大学, 28 Apr. 2021 - 31 Mar. 2024

  褐虫藻は酸素発生型光合成を行う単細胞藻類の一種で、サンゴやイソギンチャクをはじめとする無脊椎動物を宿主として共生を行うことで知られている。近年、共生している褐虫藻がサンゴから排出されてしまうというサンゴの白化現象が問題となっている。サンゴの白化は、水温が上限より数℃高い状態が続くだけで時に大規模なスケールで一斉に起こり、周辺の豊かな生態系が失われてしまう。しかし、共生系における代謝レベルから見た白化現象の分子メカニズムや数理構造は未解明のまま残されている。本研究の目的は、褐虫藻-サンゴ共生系における細胞内のレドックスや代謝変化と共生系全体の動態（白化現象）の関係を明らかにし、生態系全体の動態（白化現象）の予測に重要な代謝および数理的ファクターを見つけることである。 白化現象の進行には活性酸素種によるストレスが関係していると考えられている。そこで、本研究では白化が始まる過渡期のレドックス状態変化の理解が、白化現象の進行の理解に重要と考え、細胞内代謝物の中でもNAD(P)、グルタチオンのレドックス状態を中心に解析を行う。この解析実施を目指し、サンゴにおけるNAD(P)、グルタチオンのレドックス状態の正確な定量系を確立する必要がある。そこで2021年度には、もっとも単純な光合成微生物のシアノバクテリアをモデルとして、13C同位体内部標準を用いた正確な代謝物定量系を立ち上げた。このシステムでは、代謝物抽出処理における酸素などによる酸化や検出時のイオンサプレッション効果などの人為的な影響を排除でき、正確なレドックス定量が可能である。


• Development of a comprehensive protein potential determination method to elucidate the adaptation mechanism of photosynthesis

  Japan Science and Technology Agency JST, Strategic Basic Research Programs_ACT-X, Oct. 2022, Principal investigator


• 光合成の光環境適応におけるレドックスシグナル伝達機構の解明

  田中 謙也

  日本学術振興会, 科学研究費助成事業 特別研究員奨励費, 特別研究員奨励費, 大阪大学, 25 Apr. 2018 - 31 Mar. 2021

  本年度は、研究課題であるレドックスシグナル伝達機構と関連する細胞内レドックス状態について基礎的知見を得るため、以下に示す研究に取り組んだ。 シアノバクテリアにおいてNADP(H)は光合成反応をはじめ、多くの代謝反応およびレドックスシグナル伝達に関与する重要な酸化還元コファクターであり、広範な生理学的プロセスを協調的に機能させるには細胞内NADP+/NADPH比は適切な範囲に制御される必要があると考えられている。しかし、これまでに定量されたNADP+/NADPH比の値には大きな差異がある。そこで、シアノバクテリアSynechocystis sp. PCC 6803に対し、新たなNADP(H)抽出方法を適用することでNADP+/NADPH比の光応答を調べた。野生株およびNAD(P)H dehydrogenaseが欠損した変異株の両方において、抽出法によって得られたNADP(H)の光応答はin vivoで測定されたNADPH蛍光の時間変化と定性的に一致した。重要なことに、すべてのNADP(H)が明暗変化によって酸化もしくは還元されるわけではないことが抽出法によって明らかとなった。これらの知見をまとめた論文は、Photosynthesis Research誌（査読有り）に受理された。 この他に、レドックスシグナルとして重要である活性酸素種（ROS）レベルと概日時計との間に強い相関があることを明らかにした。この成果は論文としてとりまとめ、Scientific Reports誌（査読有り）に受理された。 さらに、細胞外へのレドックスシグナルに関連して、シアノバクテリアのアノード電流生成と水酸化鉄還元量はグルコース添加によって大きく増加することが明らかとなった。この結果をとりまとめた論文は、Frontiers in Microbiology誌（査読有り）に受理された。

• 藻類を用いてＤ－グルコースを生産する方法

  特願2024-152689, 04 Sep. 2024, 国立大学法人神戸大学, 学校法人東京女子医科大学

  Patent right

  IRI