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Journal Articles

Effect of uranium (VI) on the growth of yeast and influence of metabolism of yeast on adsorption of U (VI)

Sakamoto, Fuminori; Onuki, Toshihiko; Kozai, Naofumi; Wakai, Eiichi; Fujii, Tsutomu*; Iefuji, Haruyuki*; Francis, A. J.

Journal of Nuclear and Radiochemical Sciences, 6(1), p.99 - 101, 2005/07

We have carried out the growth experiments of 3 strains of yeast in a medium containing uranium (VI) to elucidate the effect of U (VI) on the growth of microorganisms. Hansenula fabianii J640 grew in the liquid medium containing 0.1 mM U (VI) at lower rate than the control, but Saccharomyces cerevisiae did not grow under this condition. The H. fabianii J640 pre-cultured for 21 h in the liquid medium without U (VI) grew even after the exposure to 1 mM U (VI), but did not grow without pre-cultivation. For the pre-cultured H. fabianii J640, radioactivity of U in the medium was the same as the initial one for 110 h, and then gradually decreased. TEM-EDS analysis of H. fabianii J640 exposed to 1 mM U (VI) for 165 h showed accumulation of U (VI) on the cells. When H. fabianii J640 was not pre-cultured, radioactivity of U in the medium was lower than the initial one. These results indicated that U (VI) inhibits the growth of yeast, and that the adsorption of U (VI) by the cells depends on the metabolism of yeast.

Journal Articles

Study on stabilization effect of neutral soft donor on trivalent lanthanide and actinide dicarboxylate complexes by time-resolved laser-induced fluorescence spectroscopy

Sasaki, Takayuki*; Kubo, Shintaro*; Kobayashi, Taishi*; Kirishima, Akira*; Kimura, Takaumi; Kubota, Takumi*; Takagi, Ikuji*; Moriyama, Hirotake*

Journal of Nuclear and Radiochemical Sciences, 6(1), p.51 - 54, 2005/07

no abstracts in English

Journal Articles

Effect of Eu(III) on the degradation of malic acid by ${it Pseudomonas fluorescens}$ and the subsequent production of pyruvic acid

Nankawa, Takuya; Suzuki, Yoshinori*; Ozaki, Takuo; Onuki, Toshihiko; Francis, A. J.*

Journal of Nuclear and Radiochemical Sciences, 6(1), p.95 - 98, 2005/07

We studied the biodegradation of Eu(III)-malic acid complexes by ${it Pseudomonas fluorescens}$. L-malic acid can be found in the environment and is one of the microbial metabolites which are formed in the TCA cycle. Malic acid was degraded in the absence and in the presence of Eu(III) of 0.05, 0.1, and 0.2 mM. The degradation rate of malic acid increased with decreasing the ratios of Eu(III) to malic acid. These results suggest that the toxicity of Eu(III) can be masked through its complexation with malic acid. The degradation of malic acid was followed by the production of unidentified organic acids which showed higher affinities with Eu(III) than malic acid. Our findings suggest that organic acid with a low chelating ability can influence the environmental behavior of Eu(III) by biologically transformed into the one with a higher chelatingability and through subsequent complexation with Eu(III).

Journal Articles

Adsorption of Th(IV) and Pu(IV) on the surface of ${it Pseudomonas fluorescens}$ and ${it Bacillus subtilis}$ in the presence of desferrioxamine siderophore

Yoshida, Takahiro*; Ozaki, Takuo; Onuki, Toshihiko; Francis, A. J.

Journal of Nuclear and Radiochemical Sciences, 6(1), p.77 - 80, 2005/07

Thorium(IV) adsorption on bacterial cells in the presence of DFO was larger than that of Pu(IV) because of the smaller stability of the Th(IV)-DFO complex than that of the Pu(IV)-DFO complex. On the other hand, adsorption of Pu(IV) was larger than that of Fe(III), where in the stability of the Pu(IV)- and Fe(III)-DFO complex is comparable. P. fluorescens showed a higher affinity for Th(IV) and Pu(IV) than B. subtilis, though potentiometric titration of bacterial cells indicated that surfaces of P. fluorescens and B. subtilis cells showed similar proton binding properties.

Journal Articles

Cs accumulation behavior by ${it Pseudomonas fluorescens}$

Nakao, Atsushi*; Yoshida, Takahiro*; Ozaki, Takuo; Onuki, Toshihiko; Funakawa, Shinya*; Kozaki, Takashi*

Journal of Nuclear and Radiochemical Sciences, 6(1), p.107 - 110, 2005/07

Cs accumulation by Pseudomonas fluorescens was examined under conditions of growth and resting to elucidate the interaction between Cs and bacteria. In the growth condition, P. fluorescens did not accumulate Cs irrespective of the presence of K. In the resting condition, the cells quickly adsorbed approximately 5 $$mu$$mol Cs/gcell dry-weight and subsequently released approximately 90 % of the adsorbed Cs with 1 M CH$$_{3}$$COONH$$_{4}$$. The amount of Cs adsorption by cells of P. fluorescens varied with changing pH and ionic strength of the solution. These results indicate that Cs accumulation by P. fluorescens occurs mainly by reversible adsorption on the cell walls, but not by intracellular accumulation under nutrient conditions.

Journal Articles

Ion transport across a bilayer lipid membrane in the presence of a hydrophobic ion or an ionophore

Shirai, Osamu*; Uehara, Akihiro*; Yamana, Hajimu*; Onuki, Toshihiko; Yoshida, Yumi*; Kihara, Sorin*

Journal of Nuclear and Radiochemical Sciences, 6(1), p.55 - 60, 2005/07

The ion transport from one aqueous phase (W1) to another (W2) across a bilayer lipid membrane (BLM) in a cell system in the presence of a hydrophobic ion or an ionophore was investigated by voltammetry. The hydrophobic ion was distributed into the BLM with the counter ion to hold the electroneutrality within the BLM. It was pointed out that the counter ion could transfer between W1 and W2 across the BLM since concentrations of the counter ion in W1, BLM and W2 were so high as to cause the ion transfer current while concentrations of the hydrophobic ion were very low. The facilitated transports of alkali ions across a BLM containing valinomycin (Val) used as an ionophore were also investigated by considering the hydrophobicity of both the objective cation and the counter anion and the formation of the alkali metal ion-Val complex..

Journal Articles

Accumulation of Cu and its oxidation state in ${it Tremolecia atrata}$ (rusty-rock lichen) mycobiont

Fujii, Hiromitsu*; Hara, Kojiro*; Komine, Masashi*; Ozaki, Takuo; Onuki, Toshihiko; Yamamoto, Yoshikazu*

Journal of Nuclear and Radiochemical Sciences, 6(1), p.115 - 118, 2005/07

We studied the association of a Cu tolerant mycobiont, Tremolecia atrata (rusty-rock lichen) with Cu. T. atrata mycobiont cell aggregates, which grew into a sperical shape, rapidly absorbed Cu into their inner and outer parts. The EDS/SEM study showed that Cu was more highly accumulated in the inner part than the outer part of the aggregates. The XANES study revealed that the Cu absorbed by the T. atrata mycobiont was both monovalent and divalent. These results suggested that the T. atrata mycobiont's high tolerance to Cu is attributable to its ability to store Cu(I) inside the cytoplasm and to adsorb Cu(II) on the cell wall.

Journal Articles

Sorption of Eu(III) on ${it Pseudomonas fluorescens}$ in the presence of citric acid

Suzuki, Yoshinori; Nankawa, Takuya; Yoshida, Takahiro*; Ozaki, Takuo; Onuki, Toshihiko; Francis, A. J.*; Tsushima, Satoru*; Enokida, Yoichi*; Yamamoto, Ichiro*

Journal of Nuclear and Radiochemical Sciences, 6(1), p.91 - 93, 2005/07

We studied the sorption of Eu(III) on Pseudomonas fluorescens in the absence and presence of citric acid by a batch method. The cells were placed in a solution containing 0.002 mM of Eu(III) and 0, 0.1, or 1 mM of citric acid at pH 3-9 for 5 hours. In the absence of citric acid, almost 100 % of Eu(III) was sorbed on P. fluorescens at pHs below 7; above 7, sorption decreased with an increase in pH. The time course of Eu(III) sorption on P. fluorescens showed that a fraction of it was desorbed into the solution at alkaline pHs, suggesting that the bacterium may release some exudates. With citric acid present, we found that at higher concentrations there was lower sorption of Eu(III), reflecting the formation of Eu(III)-citrate complexes competes with the Eu(III)-cell-surface complexes. This decrease in Eu(III) sorption was significant in alkaline pHs.

Journal Articles

Solubility Product of Tetravalent Neptunium in the Reducing Condition

Fujiwara, Kenso; Kohara, Yukitoshi*

Advanced Science Research(ARS2004) Advances in Heavy Elements Microbiology Research p.37, P. 37, 2004/00

Focusing on the cover layer materials (as the Radon Barrier Materials), which could have the effect to restrain the radon from scattering into the air and the effect of the radiation shielding, we produced the radon barrier materials with crude bentonite on an experimental basis, using the rotary type comprehensive unit for grinding and mixing, through which we carried out the evaluation of the characteristics thereof.

Journal Articles

Influence of bacteria on deep groundwater in relation to geological disposal

Aoki, Kazuhiro

Proceedings of 4th International Symposium on Advanced Science Research (ASR 2004), 0 Pages, 2004/00

Microbial activity can have a significant impact on geochemical processes as it can influence mineral dissolution and precipitation, pH, aokalinity and redox. Laboratory experiments have shown that microbial activity can influence rock-water interactions even in nutrient-poor-conditions.

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