Accumulation of rare earth elements by siderophore-forming <Emphasis Type="Italic">Arthrobacter luteolus</Emphasis> isolated from rare earth environment of Chavara,India

In this study, Arthrobacter luteolus, isolated from rare earth environment of Chavara (Quilon district, Kerala, India), were found to produce catechol-type siderophores. The bacterial strain accumulated rare earth elements such as samarium and scandium. The siderophores may play a role in the accumulation of rare earth elements. Catecholate siderophore and low-molecular-weight organic acids were found to be present in experiments with Arthrobacter luteolus. The influence of siderophore on the accumulation of rare earth elements by bacteria has been extensively discussed.     

Accumulation and fractionation of rare earth elements (REEs) in the naturally grown Phytolacca americana L. in southern China

The widespread use of rare earth elements (REEs) has resulted in problems for soil and human health. Phytolacca americana L. is a herbaceous plant widely distributed in Dingnan county of Jiangxi province, China, which is a REE mining region (ion absorption rare earth mine) and the soil has high levels of REEs. An investigation of REE content of P. americana growing naturally in Dingnan county was conducted. REE concentrations in the roots, stems, and leaves of P. americana and in their rhizospheric soils were determined. Results showed that plant REEs concentrations varied among the sampling sites and can reach 1040 mg/kg in the leaves. Plant REEs concentrations decreased in the order of leaf > root > stem and all tissues were characterized by a light REE enrichment and a heavy REE depletion. However, P. americana exhibited preferential accumulation of light REEs during the absorption process (from soil to root) and preferential accumulation of heavy REEs during the translocation process (from stem to leaf). The ability of P. americana to accumulate high REEs in the shoot makes it a potential candidate for understanding the absorption mechanisms of REEs and for the phytoremediation of REEs contaminated soil.     

The variation of REE (rare earth elements) patterns in soil-grown plants: a new proxy for the source of rare earth elements and silicon in plants

Rare earth elements (REEs) in five species of soil-grown plants (Taxodium japonicum, Populus sieboldii, Sasa nipponica, Thea sinensis and Vicia villosa) and in the soil on which each plant grew were determined with an inductively coupled plasma mass spectrometer (ICP-MS) in order to observe the variation in the distribution of REEs and to elucidate their source in soil-grown plants. The plant samples were divided into root (secondary root and main root), trunk (stem) and leaf; the soils into water soluble (soil_{soluble fraction}), HCl and HNO₃ soluble (soil_{non-silicate fraction}) and HF soluble (soil_{silicate fraction}). The REE abundances of samples were compared using REE patterns where the abundances were normalized to those of a chondrite and plotted on a logarithmic scale against the atomic number. All the plants showed similar REE patterns independent of species and location, and a W-shape variation (W-type tetrad effect) and abundance depletion of cerium (negative Ce anomaly) were found in each REE patterns of plants, more conspicuous tetrad effect being observed in HREE (heavier rare earth elements) region than in LREE (lighter rare earth elements) region. The overall variation of REE patterns of each secondary root was not similar to that of soil_{soluble fraction}, but similar to that of soil_{silicate fraction} except for the tetrad effect and Ce anomaly. The REE patterns can be interpreted by the idea that plants of different species take in REEs and Si from different parts in the soil. The results of this study seem to imply that Sasa nipponica and Vicia villosa take in free REEs and Si rather directly from silicate in the soil, and that a majority of REEs and Si in Taxodium japonicum and Thea sinensis are originated from the soluble fraction in the soil.     

Bioaccumulation of rare earth elements in cultured hela cells

HeLa S-3 cells were grown in minimal essential medium supplemented with 10% calf serum and 1 mM L-glutamine without adding any rare earth elements (REEs). Exponentially growing cells were collected, and dried materials were used to analyze their REE content by inductively coupled plasma-mass spectrometry. The results showed that the cells accumulated REEs in individually different manners; namely the accumulation ratio was higher in the lighter REEs than in the heavier REEs. To deduce the implication of the accumulation of REEs in HeLa cells, the accumulation ratios for REEs were compared with those of other biologically important elements. It was seen that the accumulation ratios obtained for REEs (from 31.8 [Ce] to 14.7 [Lu]) were intermediate among those of many bioelements: Fe (124), Mg (54.5), K (38.8), Cr (12.7), Na (11.8), Mn (11.3), Zn (10.7), Ca (8.8), and V (6.7).     

稀土元素对农田生态系统的影响研究进展

稀土矿的开采和冶炼、稀土农用等导致农田土壤稀土元素含量不断积累,对农田生态系统结构和功能稳定产生严重的影响。综述了近20年来国内外农田生态系统稀土元素的主要来源、分配和输出,土壤和植物中稀土元素的测定方法,稀土元素对农田生态系统中植物、微生物、动物以及人类健康影响的研究进展。探讨了农田生态系统稀土元素的毒性评价和稀土污染土壤的修复措施。最后提出开展稀土元素对农田生态系统影响研究还需要加强的一些问题。     

Urinary Monitoring of Exposure to Yttrium, Scandium, and Europium in Male Wistar Rats

On the assumption that rare earth elements (REEs) are nontoxic, they are being utilized as replacements of toxic heavy metals in novel technological applications. However, REEs are not entirely innocuous, and their impact on health is still uncertain. In the past decade, our laboratory has studied the urinary excretion of REEs in male Wistar rats given chlorides of europium, scandium, and yttrium solutions by one-shot intraperitoneal injection or oral dose. The present paper describes three experiments for the suitability and appropriateness of a method to use urine for biological monitoring of exposure to these REEs. The concentrations of REEs were determined in cumulative urine samples taken at 0?C24?h by inductively coupled plasma atomic emission spectroscopy, showing that the urinary excretion of REEs is <2?%. Rare earth elements form colloidal conjugates in the bloodstream, which make high REEs accumulation in the reticuloendothelial system and glomeruli and low urinary excretion. The high sensitivity of inductively coupled plasma?Cargon emission spectrometry analytical methods, with detection limits of <2???g/L, makes urine a comprehensive assessment tool that reflects REE exposure. The analytical method and animal experimental model described in this study will be of great importance and encourage further discussion for future studies.     

长期喷施稀土对土壤-植物(小麦)系统中稀土元素分布、累积及运移的影响

在我国施用稀土时间最长的黑龙江省花园农场,研究比较了施用稀土12 a和不施稀土的对照处理上小麦和土壤中的稀土元素的分布、累积及运移.结果表明,长期叶面喷施稀土并未造成耕层土壤和下部土层的稀土元素的累积.成熟期小麦植株各部位的稀土元素含量顺序为根>叶>茎、壳;稀土元素主要累积在根部,其次是叶,茎和壳累积较少.喷施处理小麦根部的稀土元素累积量高于对照,叶部也有此趋势,而茎、壳等部位差异不大.根、茎、叶、壳稀土元素分布模式与土壤中相似,与施用的常乐稀土差别较大;长期喷施稀土未曾造成籽粒中稀土元素的明显累积.     

混合稀土对作物出苗率的影响

用OECD方法,在红壤、黄潮土、黄褐土上进行了混合稀土对水稻、油菜、大豆相对出苗率影响的试验,从LC50（半致死浓度）值看,在供试条件下,稀土对水稻的毒性最小,稀土在黄褐土上对作物的毒性也较小,而稀土对黄潮土上的大豆以及红壤上的油菜的毒性则较大。     

镧在草-菇-土系统中的循环与生物富集效应

利用稀土镧肥种植牧草南非马唐,采用含镧牧草栽培杏鲍菇和以菇渣作为有机肥种植牧草进行连续性试验,研究镧在草-菇-土系统中的分配与生物富集情况。结果表明：施镧处理的南非马唐和杏鲍菇各器官的镧元素含量均高于不施镧处理,其中镧在牧草南非马唐中的分布为根>叶>茎,镧在杏鲍菇中的分布为菌盖>菌柄;外源镧进入土壤以后,南非马唐不同器官的镧元素生物富集系数均随着镧施入量的增加而增大,其中以根的镧生物富集系数最大,介于0.443—0.580之间。除高剂量（M4）处理外,叶和茎的镧生物富集系数不同处理间无显著差异,但根出现明显变化;含镧牧草栽培杏鲍菇和菇渣种植南非马唐后,不同器官的镧含量无显著增加,说明镧残留在草-菇-土系统中迁移转化效率降低。     

茶园土壤类型对铁观音茶叶稀土元素分布和组成的影响

为探明铁观音茶的质量安全状况,追溯隐患来源,对福建安溪县不同土壤茶园的铁观音茶叶进行稀土元素的分布、组成、迁移和富集能力进行研究。结果表明,安溪县红壤、黄红壤、黄壤茶园稀土组成均以镧、铈、钕、钇为主,但具体组成特征各异。3种类型土壤茶园铁观音茶叶片、叶柄稀土元素组成均以钇、镧、铈、钕4种元素为主,且含量均以第3叶第2叶第1叶叶柄。同种土壤类型茶园铁观音茶树不同部位叶片的稀土元素组成特征类似,但叶与叶柄对稀土元素的吸收能力不同。土壤类型对茶叶稀土元素的累积有显著影响,黄红壤茶园的茶叶稀土元素含量要显著低于红壤、黄壤茶园的(P0.05)。土壤与茶叶中稀土元素组成的相关系数为0.886～0.985,P 0.001,表明二者稀土元素组成密切相关。因此,铁观音茶叶中稀土元素累积、分布与茶园土壤类型有显著相关性。     

Accumulation of rare earth elements in maize plants (Zea mays L.) after application of mixtures of rare earth elements and lanthanum

Rare earth elements are applied in China to improve crop production, and the distribution patterns of individual rare earth elements in native plants have widely been reported. But our knowledge is still limited about the dose-dependent accumulation of individual rare earth elements in agricultural crops after application of rare earth elements. Effects of lanthanum and mixtures of rare earth elements were studied in pot experiments on the accumulation of individual rare earth elements in maize plants. All plant samples were divided into plant tops and roots. On addition of mixtures of rare earth elements and lanthanum to the soil, a significant dose-dependent accumulation of individual rare earth element(s) was found in the roots and in the plant tops. Application of mixtures of rare earth elements at >10 mg kg^–1 soil, resulted in a significant increase in contents of light rare earth elements in the roots, and at a dose of 50 mg kg^–1 soil, a similar phenomenon was found in the plant tops. When mixtures of rare earth elements were replaced by lanthanum alone, at a dose higher than 10 mg La kg^–1 soil, a significant increase in La content occurred in the roots and in the plant tops. The content ratio of La to Ce in maize plants appeared to increase as the application doses of rare earth element(s) increased. At a highest dose (50 mg kg^–1soil), the transport of the absorbed La from the roots to the plant tops might be substantially reduced after treatment with lanthanum alone, compared with mixtures of rare earth elements. Increasing the application doses of rare earth element(s) appeared to cause a positive Gd and negative Ce anomaly in the roots and in the plant tops, and the anomaly was more obvious in the plant tops than in the roots. The results indicated that the Gd and Ce anomaly in corns might be considered as important parameters for the safety assessment of agricultural application of rare earth elements.     

Genetic Diversity of Bacillus cereus/B. thuringiensis Isolates from Natural Sources

The genetic diversity and relationships among 154 Bacillus cereus/B. thuringiensis isolates recovered from soil samples from five geographic areas in Norway were investigated with multilocus enzyme electrophoresis (MEE). Cluster analysis revealed two major groups (designated cluster I and cluster II) separated at genetic distance greater than 0.55. Cluster I included 62 electrophoretic types (ETs) originating from all five locations, whereas, in cluster II, all but one isolate were from the same location. The isolates were also serotyped with B. thuringiensis flagellar antisera, and 28 distinct serotypes were identified. In general, serotyping did not show correlation to the genetic diversity of the isolates. The presence of IS231- and IS240-like transposable elements was detected in 14% of the strains of cluster II only. Parasporal crystals were observed in three strains; ten other strains were toxic to Trichoplusia ni. We conclude that B. cereus/B. thuringiensis from soil exhibit a high degree of recombination. Received: 15 December 1997 / Accepted: 26 January 1998     

New resource assessment characterization factors for rare earth elements: applied in NdFeB permanent magnet case study

The International Journal of Life Cycle Assessment - Rare earth elements (REEs) are among the most critical raw materials with a high supply risk. Despite their criticality, REEs are not covered by...     

Evaluation of Some Fungi and Bacteria for Potential Control of Safflower Rust

Some fungal and bacterial isolates applied as soil and seed treatments in greenhouse trials gave a good protection against Puccinia carthami Cda. on safflower, significantly reducing the infection from rust-infested seeds. Trichoderma viride and T. harzianum added alone and in combination as air-dried inoculum to the soil were the most effective fungal isolates. However T. viride at two higher rates reduced the rate of emergence of safflower seedlings. Among bacteria, Bacillus subtilis, B. cereus, isolates of Pseudomonas fluorescens and B. thuringiensis reduced rust infection when added both as soil drench and as seed treatment. Good results in the biocontrol of P. carthami were also obtained with some combination antagonist treatments such as T. viride + B. cereus, T. viride + P. fluorescens (16), T. viride + T. harzianum + B. cereus and T. viride +, T. harzianum + P. fluorescens (16). Fungal isolates added as soil treatment increased seedling length, whereas no similar effects were observed when these isolates were applied as seed treatment.     

Macromolecules Released by a Plant Growth-promoting Rhizobacterium as Elicitors of Systemic Resistance in Tomato to Bacterial and Fungal Pathogens

One of 500 rhizobacteria isolated from soil, rhizosphere and rhizoplane of healthy tomato plants was previously selected in laboratory, greenhouse and field tests as a good inducer of systemic resistance. This plant growth‐promoting rhizobacterium (PGPR) was identified as Bacillus cereus by fatty‐acid analysis. Bacillus cereus bacterial cells were removed from liquid culture by centrifugation and the supernatant repeatedly dialyzed (cut‐off = 12 000 daltons) against distilled water. Dialysates applied to roots protected tomato plants against leaf fungal and bacterial pathogens, evidence that macromolecules synthesized by the PGPR and released into the environment act as elicitors of systemic resistance.     

Effects of citric acid and the siderophore desferrioxamine B (DFO-B) on the mobility of germanium and rare earth elements in soil and uptake in Phalaris arundinacea

Effects of citric acid and desferrioxamine B (DFO-B) on the availability of Ge and selected rare earth elements (REEs) (La, Nd, Gd, Er) to Phalaris arundinacea were investigated. A soil dissolution experiment was conducted to elucidate the effect of citric acid and DFO-B at different concentrations (1 and 10 mmol L^?1 citric acid) on the release of Ge and REEs from soil. In a greenhouse, plants of P. arundinacea were cultivated on soil and on sand cultures to investigate the effects of citric acid and DFO-B on the uptake of Ge and REEs by the plants. Addition of 10 mmol L^?1 citric acid significantly enhanced desorption of Ge and REEs from soil and uptake into soil-grown plants. Applying DFO-B enhanced the dissolution and the uptake of REEs, while no effect on Ge was observed. In sand cultures, the presence of citric acid and DFO-B significantly decreased the uptake of Ge and REEs, indicating a discrimination of the formed complexes during uptake. This study clearly indicates that citric acid and the microbial siderophore DFO-B may enhance phytoextraction of Ge and REEs due to the formation of soluble complexes that increase the migration of elements in the rhizosphere.     

Use of cluster and discriminant analyses to compare rhizosphere bacterial communities following biological perturbation

We present an approach to comparing the diversity and composition of bacterial communities from different habitats and for identifying which members of a community are most affected by an introduced bacterium. We use this method to explore both previously published and new data from field and growth chamber experiments in which we isolated heterotrophic bacteria from samples of root-free soil, roots of nontreated soybean seedlings, and from the roots of soybean seedlings grown from Bacillus cereus UW85nl—treated seeds. We characterize bacterial isolates for 40 physiological attributes, and grouped the isolates hierarchically using two-stage density-linkage cluster analysis. Multivariate analysis of variance and discriminant analysis of the relative frequencies of the clusters in the soil and rhizosphere habitats were then used to determine whether there were differences among the bacterial communities from the various habitats, and which of the clusters were most useful in discriminating among the communities. We used rarefied estimates of richness as a measure of community diversity in the various habitats. Introduction of UW85n 1 affected the composition and/or diversity of rhizosphere communities in three of four experiments. Present address: Department of Environmental Science, Policy and Management, 108 Hilgard Hall, University of California, Berkeley, CA 94720 Correspondence to: G.S. Gilbert.     

Study on binding of REEs with water-soluble polysaccharides in fern

The binding of rare earth elements (REEs) with water-soluble polysaccharides of nondeproteinization and deproteinization in the leaves of the fernDicranopteris dichotoma was studied by molecular activation analysis (MAA). Two cold-water-soluble polysaccharides (extracted by 75% ethanol and 90% ethanol, respectively) and one hot-water-soluble polysaccharide (extracted by 90% ethanol) were separated using biochemical separation techniques. The eight rare earth elements (La, Ce, Nd, Sm, Eu, Tb, Yb, and Lu) in these polysaccharides were determined by instrumental neutron activation analysis. Our new results showed that the REEs were bound firmly with the water-soluble polysaccharides in the plant, regardless of whether nondeproteinization or deproteinization was used. The molecular-weight (MW) measurement demonstrated that REEs were mainly bound with low-MW (10,000–20,000) polysaccharides.     

Diagnostic properties of three conventional selective plating media for selection of <Emphasis Type="Italic">Bacillus cereus</Emphasis>, <Emphasis Type="Italic">B. thuringiensis</Emphasis> and <Emphasis Type="Italic">B. weihenstephanensis</Emphasis>

The aim of this study was to assess the diagnostic properties of the two selective plating media and a chromogenic medium for identification of Bacillus cereus. The 324 isolates were B. cereus (37%), Bacillus weihenstephanensis (45%) or Bacillus thuringiensis (18%), as identified by a new combination of techniques. All isolates were growing on mannitol–egg yolk–polymyxin agar (MYP), and they did not form acid from mannitol. However, a significant lower number of B. thuringiensis isolates did not show lecithinase activity. All isolates were also growing on polymyxin–egg yolk–mannitol–bromothymol blue agar (PEMBA); however, 11% isolates indicated that they did produce acid from mannitol, and 15% isolates did not show any lecithinase activity. Five of the isolates did not grow at all on the chromogenic agar, and 14 of the growing isolates were β-glucosidase negative. It is concluded that the two recommended selective plating media MYP and PEMBA for detection of B. cereus group bacteria both have their limitations for identification of some B. cereus, B. weihenstephanensis or B. thuringiensis. However, MYP is preferable compared to PEMBA. The chromogenic medium has its own advantages and limitations, and some of the limitations seem to be solved by incubation at 30°C instead of the recommended 37°C.     

Occurrence and pathogenic potential of Bacillus cereus group bacteria in a sandy loam

The major part (94%) of the Bacillus cereus-like isolates from a Danish sandy loam are psychrotolerant Bacillus weihenstephanensis according to their ability to grow at temperatures below 7 °C and/or two PCR-based methods, while the remaining 6% are B. cereus. The Bacillus mycoides-like isolates could also be␣divided into psychrotolerant and mesophilic isolates. The psychrotolerant isolates of B. mycoides could␣be discriminated from the mesophilic by the two PCR-based methods used to characterize B.␣weihenstephanensis. It is likely that the mesophilic B. mycoides strains are synonymous with Bacillus pseudomycoides, while psychrotolerant B. weihenstephanensis, like B. mycoides, are B. mycoides senso stricto. B. cereus is known to produce a number of factors, which are involved in its ability to cause gastrointestinal and somatic diseases. All the B. cereus-like and B. mycoides like isolates from the sandy loam were investigated by PCR for the presence of 12 genes encoding toxins. Genes for the enterotoxins (hemolysin BL and nonhemolytic enterotoxin) and the two of the enzymes (cereolysin AB) were present in the major part of the isolates, while genes for phospolipase C and hemolysin III were present in fewer isolates, especially among B. mycoides like isolates. Genes for cytotoxin K and the hemolysin II were only present in isolates affiliated to B. cereus. Most of the mesophilic B. mycoides isolates did not possess the genes for the nonhemolytic enterotoxin and the cereolysin AB. The presence of multiple genes coding for virulence factors in all the isolates from the B. cereus group suggests that all the isolates from the sandy loam are potential pathogens.