Updated on 2022/08/10


Faculty of Science and Engineering, School of Advanced Science and Engineering
Job title
Assistant Professor(without tenure)


  • Transcriptome Analysis of the Ammonia-Oxidizing Bacterium Nitrosomonas mobilis Ms1 Reveals Division of Labor between Aggregates and Free-living Cells.

    Rino Isshiki, Hirotsugu Fujitani, Satoshi Tsuneda

    Microbes and environments   35 ( 2 )  2020  [Refereed]  [Domestic journal]

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    Bacteria change their metabolic states to increase survival by forming aggregates. Ammonia-oxidizing bacteria also form aggregates in response to environmental stresses. Nitrosomonas mobilis, an ammonia-oxidizing bacterium with high stress tolerance, often forms aggregates mainly in wastewater treatment systems. Despite the high frequency of aggregate formation by N. mobilis, its relationship with survival currently remains unclear. In the present study, aggregates were formed in the late stage of culture with the accumulation of nitrite as a growth inhibitor. To clarify the significance of aggregate formation in N. mobilis Ms1, a transcriptome analysis was performed. Comparisons of the early and late stages of culture revealed that the expression of stress response genes (chaperones and proteases) increased in the early stage. Aggregate formation may lead to stress avoidance because stress response genes were not up-regulated in the late stage of culture during which aggregates formed. Furthermore, comparisons of free-living cells with aggregates in the early stage of culture showed differences in gene expression related to biosynthesis (ATP synthase and ribosomal proteins) and motility and adhesion (flagella, pilus, and chemotaxis). Biosynthesis genes for growth were up-regulated in free-living cells, while motility and adhesion genes for adaptation were up-regulated in aggregates. These results indicate that N. mobilis Ms1 cells adapt to an unfavorable environment and grow through the division of labor between aggregates and free-living cells.

    DOI PubMed

  • Stochastic expression of lactate dehydrogenase A induces Escherichia coli persister formation.

    Naoki Yamamoto, Rino Isshiki, Yuto Kawai, Daiki Tanaka, Tetsushi Sekiguchi, Shinya Matsumoto, Satoshi Tsuneda

    Journal of bioscience and bioengineering   126 ( 1 ) 30 - 37  2018.07  [Refereed]  [Domestic journal]

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    Bacterial persisters are phenotypic variants that survive the treatment of lethal doses of growth-targeting antibiotics without mutations. Although the mechanism underlying persister formation has been studied for decades, how the persister phenotype is switched on and protects itself from antibiotics has been elusive. In this study, we focused on the lactate dehydrogenase gene (ldhA) that was upregulated in an Escherichia coli persister-enriched population. A survival rate assay using an ldhA-overexpressing strain showed that ldhA expression induced persister formation. To identify ldhA-mediated persister formation at the single-cell level, time-lapse microscopy with a microfluidic device was used. Stochastic ldhA expression was found to induce dormancy and tolerance against high-dose ampicillin treatment (500 μg/ml). To better understand the underlying mechanism, we investigated the relationship between ldhA-mediated persister formation and previously reported persister formation through aerobic metabolism repression. As a result, ldhA expression enhanced the proton motive force (PMF) and ATP synthesis. These findings suggest that ldhA-mediated persister formation pathway is different from previously reported persister formation via repression of aerobic metabolism.

    DOI PubMed

Research Projects

  • Toxinファージデリバリーシステムによる薬剤耐性菌問題の解決

    日本学術振興会  科学研究費助成事業 若手研究

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    一色 理乃

Specific Research

  • Toxinデリバリーシステムによる耐性菌問題の解決


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  • ファージを介したToxinによる感染症病原菌の除去


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  • 表現型不均一性の形成に関連する遺伝子発現の解析


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