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U accumulations in 
naturally growing at the mill tailings pond; Iron plaque formation possibly related to root-endophytic bacteria producing siderophoresNakamoto, Yukihiro*; Doyama, Kohei*; Haruma, Toshikatsu*; Lu, X.*; Tanaka, Kazuya; Kozai, Naofumi; Fukuyama, Kenjin; Fukushima, Shigeru; Ohara, Yoshiyuki; Yamaji, Keiko*
Minerals (Internet), 11(12), p.1337_1 - 1337_17, 2021/12
Times Cited Count：1 Percentile：10.87(Geochemistry & Geophysics)Mine drainage is a vital water problem in the mining industry worldwide because of the heavy metal elements and low pH. Rhizofiltration using wetland plants is an appropriate method to remove heavy metals from the water via accumulation in the rhizosphere. is one of the candidate plants for this method because of metal accumulation, forming iron plaque around the roots. At the study site, which was the mill tailings pond in the Ningyo-toge uranium mine, 
has been naturally growing since 1998. The results showed that accumulated Fe, Mn, and U in the nodal roots without/with iron plaque compared with other plant tissues. Among the 837 bacterial colonies isolated from nodal roots, 88.6% showed siderophore production activities. Considering iron plaque formation around roots, we hypothesized that microbial siderophores might influence iron plaque formation because bacterial siderophores have catechol-like functional groups. The complex of catechol or other phenolics with Fe was precipitated due to the networks between Fe and phenolic derivatives. The experiment using bacterial products of root endophytes, such as 
spp. and 
spp., showed precipitation with Fe ions, and we confirmed that several 
spp. and 
spp. produced unidentified phenolic compounds. In conclusion, root-endophytic bacteria such as spp. and spp., isolated from metal-accumulating roots of , might influence iron plaque formation as the metal accumulation site. Iron plaque formation is related to tolerance in , and spp. and spp. might indirectly contribute to tolerance.
Yamaji, Keiko*; Nakamoto, Yukihiro*; Haruma, Toshikatsu*; Doyama, Kohei*; Ohara, Yoshiyuki; Tanaka, Kazuya; Fukuyama, Kenjin; Fukushima, Shigeru
no journal, ,
no abstracts in English
U) and heavy metal (Fe, Mn) accumulation mechanism in phragmites australis influenced by root endophytic bacteriaNakamoto, Yukihiro*; Yamaji, Keiko*; Haruma, Toshikatsu*; Doyama, Kohei*; Ohara, Yoshiyuki; Tanaka, Kazuya; Fukuyama, Kenjin; Fukushima, Shigeru
no journal, ,
no abstracts in English
influenced by root endophytic bacteriaNakamoto, Yukihiro*; Yamaji, Keiko*; Haruma, Toshikatsu; Doyama, Kohei*; Ohara, Yoshiyuki; Fukuyama, Kenjin; Fukushima, Shigeru
no journal, ,
no abstracts in English
growing at the ore-sedimentary site; Iron plaque formation possibly related to endophytic bacteriaNakamoto, Yukihiro*; Doyama, Kohei*; Haruma, Toshikatsu*; Lu, X.*; Tanaka, Kazuya; Kozai, Naofumi; Fukuyama, Kenjin; Fukushima, Shigeru; Ohara, Yoshiyuki; Yamaji, Keiko*
no journal, ,
no abstracts in English
naturally growing at a sedimentation site in an uranium mine associated with endophytic bacteriaHaruma, Toshikatsu*; Yamaji, Keiko*; Nakamoto, Yukihiro*; Doyama, Kohei*; Takahashi, Yoshio*; Tanaka, Kazuya; Kozai, Naofumi; Fukuyama, Kenjin*
no journal, ,
no abstracts in English
(Cav.) Trin. ex Steud. without iron plaque formationOkuma, Miyu*; Yamaji, Keiko*; Nakamoto, Yukihiro*; Fukuyama, Kenjin*; Tsunashima, Yasumichi
no journal, ,
At our study site, mill tailing pond, which is used as a temporary storage site to treat mine water containing iron, manganese, etc., (Cav.) Trin. ex Steud. has been found to grow naturally there; therefore, this plant was considered to have some metal tolerance mechanisms. Actually, was previously reported to enhance heavy metal tolerance through the formation of iron plaques; however, few iron plaques were observed on roots of growing Fe deposition site close to the entrance of mine water at our study site, suggesting that they may have another heavy metal tolerance mechanisms. The objective of this study was to elucidate the heavy metal tolerance mechanisms of , without iron plaque formation. Elemental analysis clarified that high concentrations of Fe, Al, and Zn were accumulated in healthy nodal roots; especially, excessive Fe accumulation was confirmed compared with normal plants. Detoxicant analysis in the roots indicated that phenolics and organic acids were not produced well to contribute to the tolerance. Due to the observation of sections of nodal roots stained with potassium ferrocyanide solution, Fe localization was observed in the epidermis and the cell walls of the outermost layers of the cortex cells. Since immobilization of heavy metals in the cell walls is known as one of the heavy metal tolerance mechanisms in plants, our results suggest that would show the tolerance to immobilize Fe in the cell walls to prevent from migrating into the interior cells.
