Manganese and Arsenic Oxidation Performance of Bacterium-Yunotaki 86 (BY86) from Hokkaido,Japan, and the Bacterium's Phylogeny

We examined the Mn(II) oxidation performance of a bacterium, BY86, collected at Yunotaki Falls Hokkaido, Japan. The bacterium showed rapid oxidation of Mn(II), and brown precipitates containing Mn formed within a few days of incubation. The presence of higher oxidation states of Mn than Mn(II) was ascertained by the UV-vis and XANES sutdy. This bacterium did not oxidize As(III) to As(V) in the absence of Mn. In the presence of Mn, however, As(III) was rapidly oxidized to As(V) on the cell surfaces. These findings indicate that BY86 does not have the ability to directly oxidize As(III) to As(V) within a short period of contact, but indirectly oxidizes it by the Mn oxides generated on the cell surfaces. A phylogenetical study disclosed that BY86 was most closely related to Bacillus cereus with an identity of 99.90%. It is expected that our findings in this study will contribute to the study of Mn(II)-oxidizing bacteria, which play an important role in the biogeochemical cycling of Mn as well as other trace elements including As.     

负载型纳米铁制备条件对As(V)吸附的影响

以活性炭为载体,制备了负载型纳米铁除砷吸附剂.以除砷效率为目标,优化了制备过程中活性炭的不同粒径、铁盐种类及浓度、反应温度及速度、铁盐浸泡活性炭时间及反应平衡时间等参数.考虑到除砷效率及工程实际的应用,室温时采取活性炭粒径为20～40目、KBH4的滴加速率为lml·min-1、活性炭经铁盐为质量浓度为6.9％的硫酸亚铁浸泡30 min,反应平衡时间为30 min时所制备的吸附剂综合除砷效果最好(98％).     

A comparison of arsenic mobility in Phaseolus vulgaris, Mentha aquatica, and Pteris cretica rhizosphere

The ability of Phaseolus vulgaris, Mentha aquatica, and Pteris cretica to release arsenic (As) species from contaminated soil was tested in rhizobox experiments in three soils differing in their physicochemical parameters and total and mobile As concentration. Relatively low uptake of arsenic by P. vulgaris and M. aquatica resulted in very low and ambiguous changes in rhizosphere soil compared to bulk soil. However, there were observed differences in the distribution of the mobile As portion in soil to individual As species as affected by plant species and/or plantation conditions of these plants. Higher percentage of mobile arsenite in mint rhizosphere seems to be related to more reducing conditions during cultivation of these wetland plants. P. cretica planted in the soils containing between 36 and 1436 mg As kg⁻¹ was able to accumulate between 80 and 500 mg As kg⁻¹ in aboveground biomass. The extractable concentrations of As compounds in rhizosphere soil of P. cretica showed a clear depletion of arsenate (representing more than 90% of extractable arsenic) with the distance from plant roots. However, the As uptake mechanisms, as well as As transformation within hyperaccumulating fern plants, differ substantially from those in higher plants. Therefore the finding of suitable higher plant tolerant to the As soil contamination with good ability to accumulate As in aboveground biomass remains for the further research.     

ARSENIC CHEMISTRY AND REMEDIATION IN HAWAIIAN SOILS

Past use of arsenical pesticides has resulted in elevated levels of arsenic (As) in some Hawaiian soils. Total As concentrations of 20–100 mg/kg are not uncommon, and can exceed 900 mg/kg in some lands formerly planted with sugarcane. With high contents of amorphous aluminosilicates and iron oxides in many Hawaii's volcanic ash-derived Andisols, a high proportion (25–30%) of soil As was associated with either these mineral phases or with organic matter. Less than 1% of the total As was water soluble or exchangeable. Furthermore, the soils can sorb As strongly: the addition of 1000 mg/kg as As (+5) resulted in only between 0.03 and 0.30 mg/L As in soil solution. In contrast, soils having more crystalline minerals (e.g., Oxisols) sorb less As and thus often contain less As. Phosphate fertilization increases As bioaccessibility, whereas the addition of Fe(OH)₃ decreases it. Brake fern (Pteris vittata L.) can be used to remove some soil As. Concentrations of As in fronds varied on average from 60 mg/kg when grown on a low-As Oxisol to 350 mg/kg when grown on a high-As Andisol. Ratios of leaf As to CaCl₂-extractable soil As were 12 and 222 for the Oxisol and Andisol, respectively.     

Multiple cysteine residues are necessary for sorting and transport activity of the arsenite permease Acr3p from Saccharomyces cerevisiae

The yeast transporter Acr3p is a low affinity As(III)/H⁺ and Sb(III)/H⁺ antiporter located in the plasma membrane. It has been shown for bacterial Acr3 proteins that just a single cysteine residue, which is located in the middle of the fourth transmembrane region and conserved in all members of the Acr3 family, is essential for As(III) transport activity. Here, we report a systematic mutational analysis of all nine cysteine residues present in the Saccharomyces cerevisiae Acr3p. We found that mutagenesis of highly conserved Cys151 resulted in a complete loss of metalloid transport function. In addition, lack of Cys90 and Cys169, which are conserved in eukaryotic members of Acr3 family, impaired Acr3p trafficking to the plasma membrane and greatly reduced As(III) efflux, respectively. Mutagenesis of five other cysteines in Acr3p resulted in moderate reduction of As(III) transport capacities and sorting perturbations. Our data suggest that interaction of As(III) with multiple thiol groups in the yeast Acr3p may facilitate As(III) translocation across the plasma membrane.     

As_2O_3干预口腔鳞癌A431细胞EGFR表达的研究

目的：研究三氧化二砷（As2O3）对人口腔鳞癌A431细胞生长的抑制作用,探讨其抗肿瘤的机制。方法：合成特异性靶向到肿瘤细胞表面表皮生长因子受体（EGFR）的近红外荧光分子对比剂EGF-Cy5.5,验证试剂合成的靶向特异性。口腔鳞状细胞癌A431细胞系暴露于浓度分别为0μM,0.5μM,2.5μM和5.0μM的三氧化二砷溶液中0,24 h,48 h和72 h。共聚焦显微镜、流式细胞仪及免疫组化证实EGFR的表达水平,上述实验均测量三次,结果取平均值。结果：EGF-Cy5.5靶向荧光对比剂的标记率为68%~70%。对比对照组,越高浓度的三氧化二砷处理的肿瘤细胞其获得的细胞荧光信号强度越小,这与药物浓度越高细胞表面表达EGFR的量越少相一致。流式细胞仪显示,在72小时,作用于细胞的三氧化二砷药物浓度分别为0.5μM,2.5μM,和5.0μM,其相对应获得的细胞EGFR表达量分别为57.28±3.2%（P〈0.05）,29.91±2.2%（P〈0.01）和10.73±2.4%（P〈0.01）,明显低于对照组的细胞EGFR表达量74.42±1.8%,（P〈0.05）。结论：本研究应用近红外荧光分子成像的方法体外检测口腔鳞状细胞癌A431的EGFR表达水平,实验证明三氧化二砷对其EGFR具有明显的抑制作用,且抑制作用具有时间-剂量依赖性。     

Cu、As及其复合污染对小麦生理生态指标的影响

通过盆栽实验研究了Cu,As及其复合处理对小麦生理生态指标的影响,结果表明,少量低浓度的Cu,(500mg.kg^-1),As(5mg.kg^-1)对植物的生长无明显毒害作用,但随着其浓度的增加（Cu:1000-4000mg.kg^-1,As:15-60mg.kg^-1)则显示出一定的负效应,表现为小麦POD活性增加,叶片电导率增大,色素含量降低,根尖细胞有丝分裂指数下降,小麦生物量降低,而两者的复合处理则存在一定拮抗作用,此外,研究还表明,小麦生物量与As浓度的相关性大于Cu.     

Instances of Soil and Crop Heavy Metal Contamination in China

Both general and specific investigations of soil and crop heavy metal contamination were carried out across China. The former was focused mainly on Cd, Hg, As, Pb, and Cr in soils and vegetables in suburbs of four large cities; the latter investigated Cd levels in both soils and rice or wheat in contaminated areas throughout 15 provinces of the country. The results indicated that levels of Cd, Hg, and Pb in soils and some in crops were greater than the Governmental Standards (Chinese government limits for soil and crop heavy metal contents). Soil Cd ranged from 0.46 to 1.04?mg kg^?1, on average, in the four cities and was as high as 145?mg kg^?1 in soil and 7?mg kg^?1 in rice in the wide area of the country. Among different species, tuberous vegetables seemed to accumulate a larger portion of heavy metals than leafy and fruit vegetables, except celery. For both rice and wheat, two staple food crops, the latter seemed to have much higher concentrations of Cd and Pb than the former grown in the same area. Furthermore, the endosperm of both wheat and rice crops had the highest portion of Cd and Cr. Rice endosperm and wheat chaff accumulated the highest Pb, although the concentrations of all three metals were variable in different parts of the grains. For example, 8.3, 6.9, 1.4, and 0.6?mg kg^?1 of Pb were found in chaff, cortex, embryo, and endosperm of wheat compared with 0.11, 0.65, 0.71, and 0.19?mg kg^?1 in the same parts of rice, respectively. Untreated sewage water irrigation was the major cause of increasing soil and crop metals. Short periods of the sewage water irrigation increased individual metals in soils by 2 to 80% and increased metals in crops by 14 to 209%. Atmospheric deposition, industrial or municipal wastes, sewage sludge improperly used as fertilizers, and metal-containing phosphate fertilizers played an important role as well in some specific areas.     

Arsenic speciation in marine sediments: A comparison between two sequential extraction procedures

ABSTRACT

Arsenic distribution and mobility in marine sediments was investigated by means of total extraction and two sequential extraction procedures i.e. a modified sequential extraction procedure proposed by the European Standard, Measurementand Testing (SM&T) program, formerly the Community Bureau of Reference (BCR) procedure and a five steps sequential extraction based on the Wenzel extraction procedure, called modified Wenzel extraction. Sediments were collected from Cagliari’s harbour and Cagliari’s gulf, in Western Mediterranean Sea, Italy. The modified Wenzel extraction provided a more detailed As binding pattern and turned out to be much more appropriate than the modified SM&T procedure for gaining information regarding the mobilization of As within marine sediments. In the harbour, the largest part of As is contained in the residual fraction. At the contrary, As concentration, which is higher in the Cagliari’s gulf, is primarily associated with amorphous and crystalline hydrous Fe(Mn, Al) oxide. Moreover, this study suggests the possibility to segregate different types of marine sediments depending of human or industrial activities and to trace As contaminated marine sediments to determine the origin of contamination following the percentile of As contained in each extraction steps.