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Sakamoto, Fuminori; Nankawa, Takuya; Onuki, Toshihiko; Fujii, Tsutomu*; Iefuji, Haruyuki*
Geomicrobiology Journal, 29(5), p.470 - 476, 2012/05
Times Cited Count：6 Percentile：17.37(Environmental Sciences)We screened 4908 non-essential gene deletion mutant yeast strains for uranium sensitivity and low accumulation by growth in agar medium containing uranium. All mutant strains grew successfully on agar media containing 0 or 0.5 mM uranium for one week at 30 centigrade. Thirteen strains with single gene deletions showed reduced growth in the agar medium containing 0.5 mM uranium and were identified as uranium-sensitive mutant strains. The phosphate transporter genes of PHO86, PHO84, PHO2, and PHO87 were among the deleted genes in the uranium-sensitive mutant strains, suggesting that genes concerned with phosphate transport contribute to uranium tolerance. Seventeen single-deletion strains showed lower uranium accumulation than the wild-type after exposure to agar medium containing 0.5 mM uranium, and were identified as mutant strains with low uranium accumulation.
Kozai, Naofumi; Onuki, Toshihiko; Sakamoto, Fuminori; Suzuki, Yoshinori*; Tanaka, Kazuya*; Iefuji, Haruyuki*; Sakai, Takuro
Journal of Nuclear Science and Technology, 48(8), p.1206 - 1213, 2011/08
Times Cited Count：8 Percentile：53.37(Nuclear Science & Technology)The accumulation and chemical states change of Co have been studied to elucidate the role of yeast 
in the migration of radioactive-cobalt in the environment. These results indicate that the yeast performs higher retardation of the migration of Co in the metabolically active condition than the resting one.
to heavy element stress; Lead vs. uraniumSakamoto, Fuminori; Onuki, Toshihiko; Fujii, Tsutomu*; Iefuji, Haruyuki*
Geomicrobiology Journal, 27(3), p.240 - 244, 2010/05
Times Cited Count：8 Percentile：24.12(Environmental Sciences)We have examined the responses of in media containing Pb
ions and compared it to those in media containing UO
ions to elucidate the stress effects of heavy elements. Cultivation of 
in a medium containing 1.0
10
M Pb showed nearly the same growth as that in the control medium while growth was inhibited in the medium containing 1.010
M Pb. Backscattering electron image analyses of thin sections of cells showed that Pb had accumulated inside the cells. Two-dimensional (2D) gel electrophoresis analysis of the proteins extracted from the exposed to Pb ions showed that several specific protein spots were expressed after cultivation with Pb, that did not appear in the control medium. Our results suggest that Pb more weakly inhibits the growth of than UO, and produces different stresses in than UO.
in response to uranium exposureSakamoto, Fuminori; Nankawa, Takuya; Kozai, Naofumi; Fujii, Tsutomu*; Iefuji, Haruyuki*; Francis, A. J.; Onuki, Toshihiko
Journal of Nuclear and Radiochemical Sciences, 8(2), p.133 - 136, 2007/10
Protein expression of grown in the medium containing 
U(VI) and 
U(VI) was examined by two-dimensional gel electrophoresis. of BY4743 was grown in medium containing U of 0, 2.0, and 5.0 10 M or U of 2.5 10
(radioactivity was higher by 350 times than 2.0 10 M U) and 5.0 10 M for 112 h at 30
C. The growths of the yeast grown in the above media were in the following order: control 
2.5 10 M U 2.0 10 M U 5.0 10 M U 5.0 10 M U. This result indicated that not only radiological but also chemical effect of U reduced the growth of the yeast. The concentrations of U in the medium containing U or U decreased, suggesting U accumulation by the yeast cells. The 2-D gel electrophoresis analysis showed the appearance of several spots after exposure to U or to U but not in the control containing no uranium. These results show that the yeast cells exposed to U express several specific proteins.
Onuki, Toshihiko; Ozaki, Takuo; Yoshida, Takahiro*; Sakamoto, Fuminori; Kozai, Naofumi; Wakai, Eiichi; Francis, A. J.; Iefuji, Haruyuki*
Geochimica et Cosmochimica Acta, 69(22), p.5307 - 5316, 2005/11
Times Cited Count：48 Percentile：68.3(Geochemistry & Geophysics)no abstracts in English
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.
Onuki, Toshihiko; Sakamoto, Fuminori; Kozai, Naofumi; Ozaki, Takuo; Narumi, Issei; Francis, A. J.*; Iefuji, Haruyuki*; Sakai, Takuro; Kamiya, Tomihiro; Sato, Takahiro; et al.
Nuclear Instruments and Methods in Physics Research B, 210, p.378 - 382, 2003/09
Times Cited Count：11 Percentile：59.38(Instruments & Instrumentation)We examined the accumulation of Cs and Co, and the presence of other elements in yeast (Saccharomyces cerevisiae) cells by the particle induced X-ray emission (PIXE) system, which has low concentration detection limit of ppm, developed at the TIARA facility, JAERI, and by energy dispersive spectroscopy (EDS) equipped with scanning electron microscope. Addition of 1mM Cs did not have any effect on the growth of the yeast, whereas 0.5 mM Co inhibited its growth. Cells exposed to Cs showed an increase in Cs peak intensity, decrease in P, and no change in Fe, Zn and K with time. In the presence of Co, the intensity of Co and Fe peaks increased with time up to 21 hours while P, K and Zn exhibited no clear trend. These results suggest that PIXE is a useful technique to detect low concentration of elements in microbial cells as well as monitor their changes as function of growth.
Onuki, Toshihiko; Kozai, Naofumi; Sakamoto, Fuminori; Ozaki, Takuo; Nankawa, Takuya; Suzuki, Yoshinori; Iefuji, Haruyuki*; Francis, A. J.
no journal, ,
no abstracts in English
Sakamoto, Fuminori; Onuki, Toshihiko; Fujii, Tsutomu*; Iefuji, Haruyuki*
no journal, ,
In this study, we cultured Saccharomyces cerevisiae in media containing Pb or U with adjusted concentration and compared influence of Pb and 4U on the growth of S. cerevisiae. S. cerevisiae grew in media containing 1 10
or 1 10 M Pb, but did not grow in the medium containing 1 10 M Pb. S. cerevisiae did not grow in the medium containing 1 10 and 1 10 M U. These results indicated that inhibitory effect of U on the growth of S. cerevisiae is greater than that of Pb and that Pb and U obstruct the growth of S. cerevisiae by a different mechanism. S. cerevisiae did not grow in the medium containing 1 10 M natural U, but grew in the medium containing U with alpha radioactivity equivalent to 1 10 M natural U. These results indicated that the growth of S. cerevisiae is not influenced by chemotoxicity but radiotoxicity of 1 10 M Pb and U.
