担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

We summarize current knowledge on the roles of hydrogen sulfide (H2S) and reactive sulfur species (RSS) in bacterial strategies for survival and colonizing within the human body. Bacteria inhabiting the human body utilize H2S, derived from their host environment, as an electron donor or signaling molecule, while others generate and directly use H2S through the metabolism of sulfur-containing organic and inorganic compounds. The intracellular levels of H2S and RSS are tightly controlled by various mechanisms, enabling bacteria to acquire antibiotic resistance and obtain iron from their hosts. These processes are driven by transcription factors that specifically sense RSS, some of which are derived from H2S. The polysulfidation of specific cysteine residues in these transcription factors plays a key role in regulating the expression of related genes, thereby governing the interactions between bacteria and their hosts. The synthesis of H2S and RSS by bacteria not only affects their pathogenicity but can also influence overall health of the human host.

DOI： 10.1016/j.niox.2026.02.002

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掲載種別：研究論文（学術雑誌）  

Nontuberculous mycobacteria occasionally harbour clustered tRNA genes, referred to as a tRNA array unit, which is considered a putative antidefense system within their genomes. However, the precise genomic location of these tRNA array units remains unclear. To address this, we sequenced the complete genomes of 5 Mycobacterium avium strains carrying a tRNA array unit using a hybrid assembly of long and short reads followed by manual curation. The assemblies indicated that each strain harbours 3 to 5 extrachromosomal elements. In all genomes, the tRNA array unit was found on a linear contig exceeding 300 kb. Pulse-field gel electrophoresis (PFGE) and sodium dodecyl sulphate-PFGE revealed that the strains harbour linear plasmids corresponding to these large contigs with protein-capped termini. These linear plasmids encode a hybrid type VII/type IV secretion system but lack relaxase genes, which are typically present in mycobacterial circular plasmids. Additionally, they contain approximately 415 bp inverted repeats at the termini. Sequences of related plasmids were identified exclusively in the genomes of M. avium isolates from Japan available in public databases, suggesting a possible Asian origin. This study provides the first experimental evidence that M. avium harbours giant invertron-type linear plasmids carrying a tRNA array unit.

DOI： 10.1093/dnares/dsaf039

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

UNLABELLED: We investigated the impact of intracellular hydrogen sulfide (H2S) hyperaccumulation on the transcriptome of Escherichia coli. The wild-type (WT) strain overexpressing mstA, encoding 3-mercaptopyruvate sulfur transferase, produced significantly higher H2S levels than the control WT strain. The mstA-overexpressing strain exhibited increased resistance to antibiotics, supporting the prior hypothesis that intracellular H2S contributes to oxidative stress responses and antibiotic resistance. RNA-seq analysis revealed that over 1,000 genes were significantly upregulated or downregulated upon mstA overexpression. The upregulated genes encompassed those associated with iron uptake, including siderophore synthesis and iron import transporters. The mstA-overexpressing strain showed increased levels of intracellular iron content, indicating that H2S hyperaccumulation affects iron availability within cells. We found that the H2S-/supersulfide-responsive transcription factor YgaV is required for the upregulated expression of iron uptake genes in the mstA-overexpression conditions. These findings indicate that the expression of iron uptake genes is regulated by intracellular H2S, which is crucial for oxidative stress responses and antibiotic resistance in E. coli. IMPORTANCE: H2S is recognized as a second messenger in bacteria, playing a vital role in diverse intracellular and extracellular activities, including oxidative stress responses and antibiotic resistance. Both H2S and iron serve as essential signaling molecules for gut bacteria. However, the intricate intracellular coordination between them, governing bacterial physiology, remains poorly understood. This study unveils a close relationship between intracellular H2S accumulation and iron uptake activity, a relationship critical for antibiotic resistance. We present additional evidence expanding the role of intracellular H2S synthesis in bacterial physiology.

DOI： 10.1128/mbio.01991-24

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

ICEKKS102Tn4677 carries a bph operon for the mineralization of polychlorinated biphenyls (PCBs)/biphenyl and belongs to the Tn4371 ICE (integrative and conjugative element) family. In this study, we investigated the role of the traR gene in ICE transfer. The traR gene encodes a LysR-type transcriptional regulator, which is conserved in sequence, positioning, and directional orientation among Tn4371 family ICEs. The traR belongs to the bph operon, and its overexpression on solid medium resulted in modest upregulation of traG (threefold), marked upregulation of xis (80-fold), enhanced ICE excision and, most notably, ICE transfer frequency. We propose the evolutional roles of traR, which upon insertion to its current position, might have connected the cargo gene activation and ICE transfer. This property of ICE, i.e., undergoing transfer under environmental conditions that lead to cargo gene activation, would instantly confer fitness advantages to bacteria newly acquiring this ICE, thereby resulting in efficient dissemination of the Tn4371 family ICEs.IMPORTANCEOnly ICEKKS102Tn4677 is proven to transfer among the widely disseminating Tn4371 family integrative and conjugative elements (ICEs) from β and γ-proteobacteria. We showed that the traR gene in ICEKKS102Tn4677, which is conserved in the ICE family with fixed location and direction, is co-transcribed with the cargo gene and activates ICE transfer. We propose that capturing of traR by an ancestral ICE to the current position established the Tn4371 family of ICEs. Our findings provide insights into the evolutionary processes that led to the widespread distribution of the Tn4371 family of ICEs across bacterial species.

DOI： 10.1128/spectrum.00607-24

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Bacterial iron-sulfur (Fe-S) clusters are essential cofactors for many metabolic pathways, and Fe-S cluster-containing proteins (Fe-S proteins) regulate the expression of various important genes. However, biosynthesis of such clusters has remained unknown in genus Burkholderia. Here, we clarified that Burkholderia multivorans ATCC 17616 relies on the ISC system for the biosynthesis of Fe-S clusters, and that the biosynthetic genes are organized as an isc operon, whose first gene encodes IscR, a transcriptional regulatory Fe-S protein. Transcription of the isc operon was repressed and activated under iron-rich and -limiting conditions, respectively, and Fur, an iron-responsive global transcriptional regulator, was indicated to indirectly regulate the expression of isc operon. Further analysis using a ΔiscR mutant in combination with a constitutive expression system of IscR and its derivatives indicated transcriptional repression and activation of isc operon by holo- and apo-forms of IscR, respectively, through their binding to the sequences within an isc promoter-containing (Pisc) fragment. Biochemical analysis using the Pisc fragment suggested that the apo-IscR binding sequence differs from the holo-IscR binding sequence. The results obtained in this study revealed a unique regulatory system for the expression of the ATCC 17616 isc operon that has not been observed in other genera.

DOI： 10.1016/j.resmic.2020.06.005

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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開催年月日： 2026年3月

会議種別：シンポジウム・ワークショップ パネル（指名）  

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開催年月日： 2024年3月

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開催年月日： 2023年3月

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開催年月日： 2022年3月

会議種別：口頭発表（一般）  

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開催年月日： 2021年3月

会議種別：ポスター発表  

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