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Jun Takada - One of the best experts on this subject based on the ideXlab platform.

  • Formation of Gold Particles via Thiol Groups on Glycoconjugates Comprising the Sheath Skeleton of Leptothrix
    Geomicrobiology Journal, 2019
    Co-Authors: Tatsuki Kunoh, Hitoshi Kunoh, Mikio Takano, Yoshihiro Kusano, Minoru Takeda, Makoto Nakanishi, Syuji Matsumoto, Ichiro Suzuki, Jun Takada
    Abstract:

    Leptothrix, iron-oxidizing bacterium, produces microtubular sheaths that surround the catenulate cells. Organic nanofibrils excreted from the cell surfaces interweave and coalesce to form immature ...

  • Amino group in Leptothrix sheath skeleton is responsible for direct deposition of Fe(III) minerals onto the sheaths.
    Scientific reports, 2017
    Co-Authors: Tatsuki Kunoh, Hitoshi Kunoh, Katsunori Tamura, Noriyuki Nagaoka, Syuji Matsumoto, Kanashima Shoko, Katsuhiko Hino, Tetsuya Uchida, Jun Takada
    Abstract:

    Leptothrix species produce microtubular organic–inorganic materials that encase the bacterial cells. The skeleton of an immature sheath, consisting of organic exopolymer fibrils of bacterial origin, is formed first, then the sheath becomes encrusted with inorganic material. Functional carboxyl groups of polysaccharides in these fibrils are considered to attract and bind metal cations, including Fe(III) and Fe(III)-mineral phases onto the fibrils, but the detailed mechanism remains elusive. Here we show that NH2 of the amino-sugar-enriched exopolymer fibrils is involved in interactions with abiotically generated Fe(III) minerals. NH2-specific staining of L. cholodnii OUMS1 detected a terminal NH2 on its sheath skeleton. Masking NH2 with specific reagents abrogated deposition of Fe(III) minerals onto fibrils. Fe(III) minerals were adsorbed on chitosan and NH2-coated polystyrene beads but not on cellulose and beads coated with an acetamide group. X-ray photoelectron spectroscopy at the N1s edge revealed that the terminal NH2 of OUMS1 sheaths, chitosan and NH2-coated beads binds to Fe(III)-mineral phases, indicating interaction between the Fe(III) minerals and terminal NH2. Thus, the terminal NH2 in the exopolymer fibrils seems critical for Fe encrustation of Leptothrix sheaths. These insights should inform artificial synthesis of highly reactive NH2-rich polymers for use as absorbents, catalysts and so on.

  • Biosorption of metal elements by exopolymer nanofibrils excreted from Leptothrix cells
    Water research, 2017
    Co-Authors: Tatsuki Kunoh, Hitoshi Kunoh, Katsunori Tamura, Yoshihiro Kusano, Makoto Nakanishi, Syuji Matsumoto, Atsushi Itadani, Kota Ando, Jun Takada
    Abstract:

    Abstract Leptothrix species, aquatic Fe-oxidizing bacteria, excrete nano-scaled exopolymer fibrils. Once excreted, the fibrils weave together and coalesce to form extracellular, microtubular, immature sheaths encasing catenulate cells of Leptothrix . The immature sheaths, composed of aggregated nanofibrils with a homogeneous-looking matrix, attract and bind aqueous-phase inorganics, especially Fe, P, and Si, to form seemingly solid, mature sheaths of a hybrid organic–inorganic nature. To verify our assumption that the organic skeleton of the sheaths might sorb a broad range of other metallic and nonmetallic elements, we examined the sorption potential of chemically and enzymatically prepared protein-free organic sheath remnants for 47 available elements. The sheath remnants were found by XRF to sorb each of the 47 elements, although their sorption degree varied among the elements: >35% atomic percentages for Ti, Y, Zr, Ru, Rh, Ag, and Au. Electron microscopy, energy dispersive x-ray spectroscopy, electron and x-ray diffractions, and Fourier transform infrared spectroscopy analyses of sheath remnants that had sorbed Ag, Cu, and Pt revealed that (i) the sheath remnants comprised a 5–10 nm thick aggregation of fibrils, (ii) the test elements were distributed almost homogeneously throughout the fibrillar aggregate, (iii) the nanofibril matrix sorbing the elements was nearly amorphous, and (iv) these elements plausibly were bound to the matrix by ionic binding, especially via OH. The present results show that the constitutive protein-free exopolymer nanofibrils of the sheaths can contribute to creating novel filtering materials for recovering and recycling useful and/or hazardous elements from the environment.

  • Green Synthesis of Gold Nanoparticles Coupled with Nucleic Acid Oxidation
    2017
    Co-Authors: Tatsuki Kunoh, Hitoshi Kunoh, Mikio Takano, Minoru Takeda, Syuji Matsumoto, Ichiro Suzuki, Jun Takada
    Abstract:

    Green synthesis of metal nanoparticles, especially gold nanoparticles (AuNPs), has attracted the great interest of scientists and engineers in the medical and pharmaceutical fields; thus, a variety of ecofriendly, energy- and cost-saving techniques have been developed. In this study, we found that cells of Leptothrix (iron-oxidizing bacteria) released extracellular RNA some of which could exist as a constituent of the cell-enclosing sheaths. As a part of studies of metal encrustation in the sheaths, here we show that RNA prepared from the Leptothrix cells can reduce Au­(III) and spherical AuNPs eventually form when an aqueous HAuCl4 solution is added under ambient conditions. RNA and DNA of other organismal origins have the same ability. Of the nucleosides and nucleobases, only guanosine and guanine can form AuNPs. The DNA moiety, 2′-deoxyguanosine (dG) (used as a reference material), forms AuNPs when mixed with HAuCl4 solution, but 8-hydroxy-2′-deoxyguanosine (8-OHdG) does not, indicating that AuNP formation evidently depends on the reduction potential of the guanine moiety, not the sugar moiety. This finding is the first demonstration that spherical AuNPs of ca. 5 nm diameter can be obtained by simply adding guanine to HAuCl4 solution at ambient temperature; no other chemicals or physical treatments are needed

  • Dissociation and Re-Aggregation of Multicell-Ensheathed Fragments Responsible for Rapid Production of Massive Clumps of Leptothrix Sheaths
    Biology, 2016
    Co-Authors: Tatsuki Kunoh, Hitoshi Kunoh, Katsunori Tamura, Noriyuki Nagaoka, Ian R. Mcfarlane, Mohamed Y. El-naggar, Jun Takada
    Abstract:

    Species of the Fe/Mn-oxidizing bacteria Leptothrix produce tremendous amounts of microtubular, Fe/Mn-encrusted sheaths within a few days in outwells of groundwater that can rapidly clog water systems. To understand this mode of rapid sheath production and define the timescales involved, behaviors of sheath-forming Leptothrix sp. strain OUMS1 were examined using time-lapse video at the initial stage of sheath formation. OUMS1 formed clumps of tangled sheaths. Electron microscopy confirmed the presence of a thin layer of bacterial exopolymer fibrils around catenulate cells (corresponding to the immature sheath). In time-lapse videos, numerous sheath filaments that extended from the periphery of sheath clumps repeatedly fragmented at the apex of the same fragment, the fragments then aggregated and again elongated, eventually forming a large sheath clump comprising tangled sheaths within two days. In this study, we found that fast microscopic fragmentation, dissociation, re-aggregation and re-elongation events are the basis of the rapid, massive production of Leptothrix sheaths typically observed at macroscopic scales.

Hideki Hashimoto - One of the best experts on this subject based on the ideXlab platform.

  • Abiotic Deposition of Fe Complexes onto Leptothrix Sheaths.
    Biology, 2016
    Co-Authors: Tatsuki Kunoh, Hideki Hashimoto, Tomoko Suzuki, Katsunori Tamura, Mikio Takano, Ian R. Mcfarlane, Mohamed Y. El-naggar, Naoaki Hayashi, Eisuke Taketa, Hitoshi Kunoh
    Abstract:

    Bacteria classified in species of the genus Leptothrix produce extracellular, microtubular, Fe-encrusted sheaths. The encrustation has been previously linked to bacterial Fe oxidases, which oxidize Fe(II) to Fe(III) and/or active groups of bacterial exopolymers within sheaths to attract and bind aqueous-phase inorganics. When L. cholodnii SP-6 cells were cultured in media amended with high Fe(II) concentrations, Fe(III) precipitates visibly formed immediately after addition of Fe(II) to the medium, suggesting prompt abiotic oxidation of Fe(II) to Fe(III). Intriguingly, these precipitates were deposited onto the sheath surface of bacterial cells as the population was actively growing. When Fe(III) was added to the medium, similar precipitates formed in the medium first and were abiotically deposited onto the sheath surfaces. The precipitates in the Fe(II) medium were composed of assemblies of globular, amorphous particles (ca. 50 nm diameter), while those in the Fe(III) medium were composed of large, aggregated particles (≥3 µm diameter) with a similar amorphous structure. These precipitates also adhered to cell-free sheaths. We thus concluded that direct abiotic deposition of Fe complexes onto the sheath surface occurs independently of cellular activity in liquid media containing Fe salts, although it remains unclear how this deposition is associated with the previously proposed mechanisms (oxidation enzyme- and/or active group of organic components-involved) of Fe encrustation of the Leptothrix sheaths.

  • Bacteriogenic Iron Oxide as an Effective Catalyst for Baeyer—Villiger Oxidation with Molecular Oxygen and Benzaldehyde.
    ChemInform, 2016
    Co-Authors: Kyoko Mandai, Hideki Hashimoto, Minae Hanata, Koichi Mitsudo, Hiroki Mandai, Seiji Suga, Jun Takada
    Abstract:

    Iron oxide produced by Leptothrix ochracea catalyzes the Baeyer—Villiger oxidation with molecular oxygen in the presence of benzaldehyde at 25°C.

  • bacteriogenic iron oxide as an effective catalyst for baeyer villiger oxidation with molecular oxygen and benzaldehyde
    ChemInform, 2016
    Co-Authors: Kyoko Mandai, Hideki Hashimoto, Minae Hanata, Koichi Mitsudo, Hiroki Mandai, Seiji Suga, Jun Takada
    Abstract:

    Iron oxide produced by Leptothrix ochracea catalyzes the Baeyer—Villiger oxidation with molecular oxygen in the presence of benzaldehyde at 25°C.

  • Direct Adherence of Fe(III) Particles onto Sheaths of Leptothrix sp. Strain OUMS1 in Culture
    Minerals, 2016
    Co-Authors: Tatsuki Kunoh, Hideki Hashimoto, Hitoshi Kunoh, Tomoko Suzuki, Naoyuki Hayashi, Katsunori Tamura, Mikio Takano, Jun Takada
    Abstract:

    Leptothrix species, one of the Fe/Mn-oxidizing bacteria, oxidize Fe(II) and produce extracellular, microtubuar, Fe-encrusted sheaths. Since protein(s) involved in Fe(II) oxidation is excreted from Leptothrix cells, the oxidation from Fe(II) to Fe(III) and subsequent Fe(III) deposition to sheaths have been thought to occur in the vicinity or within the sheaths. Previously, Fe(III) particles generated in MSVP medium amended with Fe(II) salts by abiotic oxidation were directly recruited onto cell-encasing and/or -free sheaths of L. cholodnii SP-6. In this study, whether this direct Fe(III) adherence to sheaths also occurs in silicon-glucose-peptone (SGP) medium amended with Fe(0) (SGP + Fe) was investigated using another strain of Leptothrix sp., OUMS1. Preparation of SGP + Fe with Fe powder caused turbidity within a few hours due to abiotic generation of Fe(III) particles via Fe(II), and the medium remained turbid until day 8. When OUMS1 was added to SGP + Fe, the turbidity of the medium cleared within 35 h as Fe(III) particles adhered to sheaths. When primitive sheaths, cell-killed, cell-free, or lysozyme/EDTA/SDS- and proteinase K-treated sheath remnants were mixed with Fe(III) particles, the particles immediately adhered to each. Thus, vital activity of cells was not required for the direct Fe(III) particle deposition onto sheaths regardless of Leptothrix strains.

  • Use of Iron Powder to Obtain High Yields of Leptothrix Sheaths in Culture
    Minerals, 2015
    Co-Authors: Tomoko Suzuki, Hideki Hashimoto, Tatsuki Kunoh, Hitoshi Kunoh, Katsunori Tamura, Daisuke Nakatsuka, Jun Takada
    Abstract:

    The Leptothrix species, Fe-oxidizing bacteria, produce an extracellular, microtubular sheath with a complicated organic-inorganic hybrid nature. We have discovered diverse industrial functions for this material, e.g., electrode material for Li-ion batteries, catalyst enhancers, pigments, plant growth promoters, and plant protectants. To consistently obtain material with the qualitative and quantitative stability needed for industrial applications, we focused on developing an optimum culture system for sheath synthesis by the Leptothrix sp. strain OUMS1. Although we have used Fe plates as an Fe source in the liquid silicon-glucose-peptone medium (SGP), the plates do not yield a consistent quality or precise mass, and formation of Fe-encrusted sheath is restricted to a surface of the plates, which limits harvest yield. In this study, to obtain a high yield of sheaths, we cultured OUMS1 in SGP supplemented with Fe powders. The addition of Fe powders to the medium (up to 14.0 g/L) did not adversely influence growth of OUMS1. The final yield of sheaths was about 10-fold greater than in the Fe plate culture. The sheaths also maintained a microtubular form and crystalline texture similar to those produced on Fe plates

Kyoko Mandai - One of the best experts on this subject based on the ideXlab platform.

Takashi Sakai - One of the best experts on this subject based on the ideXlab platform.

Mitsuaki Furutani - One of the best experts on this subject based on the ideXlab platform.

  • A Novel Method for Culturing of Leptothrix sp. Strain OUMS1 in Natural Conditions
    Minerals, 2012
    Co-Authors: Tomoko Suzuki, Mitsuaki Furutani, Hitoshi Kunoh, Tomonori Shiraishi, Hiromichi Ishihara, Jun Takada
    Abstract:

    Although some strains of Leptothrix spp. isolated from aquatic environments have been characterized by culturing them in laboratory conditions, they often show morphological and chemical features distinct from those found in natural environments. To resolve this discrepancy, a novel cultivation method was devised for culturing such strains in natural groundwater. Leptothrix sp. strain OUMS1 was pre-cultured in a medium lacking Fe for 2 days, and then injected into a small dialysis tube bag and immersed in a container with continuously flowing groundwater for 1–3 and 14 days. Microscopic analysis of the initial phase of sheath formation and arbitrary comparisons with medium cultures revealed that in groundwater the surface coat of the sheath comprised much thinner fibrils, and an inner sheath wall that was much thinner and more indistinct compared with medium cultures. These differences were probably attributable to poorer secretion from the cell surface in groundwater conditions. A nutrient-rich medium likely activates cell metabolism and promotes secretion, resulting in a thicker inner sheath wall and thicker outer coat fibrils. Aqueous-phase Fe was deposited on immature sheaths in a similar manner in both cultures. These results indicate that laboratory culture of isolated microbes does not always reflect their characteristics in natural environments.

  • biogenous iron oxide immobilized palladium catalyst for the solvent free suzuki miyaura coupling reaction
    Tetrahedron Letters, 2012
    Co-Authors: Kyoko Mandai, Toshinobu Korenaga, Takashi Sakai, Mitsuaki Furutani, Hideki Hashimoto, Jun Takada
    Abstract:

    Abstract Iron oxide produced by iron-oxidizing bacteria, Leptothrix ochracea , (biogenous iron oxide: BIO) was used as a support for immobilized palladium catalysts with organic cross-linkers. Palladium immobilized on BIO bearing imidazolium chloride delivered the desired biaryl products in sufficient yields in the Suzuki–Miyaura coupling reactions under solvent-free conditions and could be reused several times without significant loss of catalytic activity. It is shown that BIO can be exploited as a useful support for immobilization of palladium and the BIO-immobilized palladium catalyst effectively promotes the solvent-free Suzuki–Miyaura coupling reactions.

  • Biogenous iron oxide-immobilized palladium catalyst for the solvent-free Suzuki–Miyaura coupling reaction
    Tetrahedron Letters, 2012
    Co-Authors: Kyoko Mandai, Toshinobu Korenaga, Tadashi Ema, Takashi Sakai, Mitsuaki Furutani, Hideki Hashimoto, Jun Takada
    Abstract:

    Abstract Iron oxide produced by iron-oxidizing bacteria, Leptothrix ochracea , (biogenous iron oxide: BIO) was used as a support for immobilized palladium catalysts with organic cross-linkers. Palladium immobilized on BIO bearing imidazolium chloride delivered the desired biaryl products in sufficient yields in the Suzuki–Miyaura coupling reactions under solvent-free conditions and could be reused several times without significant loss of catalytic activity. It is shown that BIO can be exploited as a useful support for immobilization of palladium and the BIO-immobilized palladium catalyst effectively promotes the solvent-free Suzuki–Miyaura coupling reactions.

  • Initial Assemblage of Bacterial Saccharic Fibrils and Element Deposition to Form an Immature Sheath in Cultured Leptothrix sp. Strain OUMS1
    Minerals, 2011
    Co-Authors: Mitsuaki Furutani, Hideki Hashimoto, Hitoshi Kunoh, Tomoko Suzuki, Hiromichi Ishihara, Jun Takada
    Abstract:

    In an aquatic environment, the genus Leptothrix produces an extracellular Fe- or Mn-encrusted tubular sheath composed of a complex hybrid of bacterial exopolymers and aqueous-phase inorganic elements. This ultrastructural study investigated initial assemblage of bacterial saccharic fibrils and subsequent deposition of aqueous-phase inorganic elements to form the immature sheath skeleton of cultured Leptothrix sp. strain OUMS1. After one day of culture, a globular and/or thread-like secretion was observed on the surface of the bacterial cell envelope, and secreted bodies were transported across the intervening space away from the cell to form an immature sheath skeleton comprising assembled and intermingled fibrils. Energy dispersive X-ray microanalysis and specific Bi-staining detected a distinguishable level of P, trace Si, and a notable amount of carbohydrates in the skeleton, but not Fe. By the second day, the skeleton was prominently thickened with an inner layer of almost parallel aligned fibrils, along with low level of Fe deposition, whereas an outer intermingled fibrous layer exhibited heavy deposition of Fe along with significant deposition of P and Si. These results indicate that basic sheath-construction proceeds in two steps under culture conditions: an initial assemblage of bacterial saccharic fibrils originated from the cell envelope and the subsequent deposition of aqueous-phase Fe, P, and Si.

  • Isolation of a Leptothrix Strain, OUMS1, from Ocherous Deposits in Groundwater
    Current microbiology, 2011
    Co-Authors: Michinori Sawayama, Mitsuaki Furutani, Hideki Hashimoto, Hitoshi Kunoh, Tomoko Suzuki, Tomonari Kasai, Naoyuki Miyata, Jun Takada
    Abstract:

    Leptothrix species in aquatic environments produce uniquely shaped hollow microtubules composed of aquatic inorganic and bacterium-derived organic hybrids. Our group termed this biologically derived iron oxide as “biogenous iron oxide (BIOX)”. The artificial synthesis of most industrial iron oxides requires massive energy and is costly while BIOX from natural environments is energy and cost effective. The BIOX microtubules could potentially be used as novel industrial functional resources for catalysts, adsorbents and pigments, among others if effective and efficient applications are developed. For these purposes, a reproducible system to regulate bacteria and their BIOX productivity must be established to supply a sufficient amount of BIOX upon industrial demand. However, the bacterial species and the mechanism of BIOX microtubule formation are currently poorly understood. In this study, a novel Leptothrix sp. strain designated OUMS1 was successfully isolated from ocherous deposits in groundwater by testing various culture media and conditions. Morphological and physiological characters and elemental composition were compared with those of the known strain L. cholodnii SP-6 and the differences between these two strains were shown. The successful isolation of OUMS1 led us to establish a basic system to accumulate biological knowledge of Leptothrix and to promote the understanding of the mechanism of microtubule formation. Additional geochemical studies of the OUMS1-related microstructures are expected provide an attractive approach to study the broad industrial application of bacteria-derived iron oxides.