Microbial reduction of metals and radionuclides

The microbial reduction of metals has attracted recent interest as these transformations can play crucial roles in the cycling of both inorganic and organic species in a range of environments and, if harnessed, may offer the basis for a wide range of innovative biotechnological processes. Under certain conditions, however, microbial metal reduction can also mobilise toxic metals with potentially calamitous effects on human health. This review focuses on recent research on the reduction of a wide range of metals including Fe(III), Mn(IV) and other more toxic metals such as Cr(VI), Hg(II), Co(III), Pd(II), Au(III), Ag(I), Mo(VI) and V(V). The reduction of metalloids including As(V) and Se(VI) and radionuclides including U(VI), Np(V) and Tc(VII) is also reviewed. Rapid advances over the last decade have resulted in a detailed understanding of some of these transformations at a molecular level. Where known, the mechanisms of metal reduction are discussed, alongside the environmental impact of such transformations and possible biotechnological applications that could utilise these activities.     

Biosynthesis of au nanoparticles by a marine bacterium and enhancing their catalytic activity through metal ions and metal oxides

The authors report that a marine Shewanella sp. CNZ-1 is capable of producing Au NPs under various conditions. Results showed that initial concentration of Au(III), pH values and electron donors affected nucleation of Au NPs by CNZ-1, resulting in different apparent color of the as-obtained bio-Au NPs, which were further characterized by UV-Vis, TEM, XRD, and XPS analyses. Mechanism studies revealed that Au(III) was first reduced to Au(I) and eventually reduced to EPS-coated Au⁰ NPs. FTIR and FEEM analyses revealed that some amides and humic acid-like matters were involved in the production of bio-Au NPs through CNZ-1 cells. In addition, the authors also found that the catalytic activity of bio-Au NPs for 4-nitrophenol (4-NP) reduction could be enhanced by various metal ions (Ca²⁺, Cu²⁺, Co²⁺, Fe²⁺, Fe³⁺, Ni²⁺, Sr²⁺, and Cr³⁺) and metal oxides (Fe₃O₄, Al₂O₃, and SiO₂), which is beneficial for their further practical application. The maximum zero-order rate constant k ₁ and first-order rate constant k₂ of all metal ions/oxides supplemented systems can reach 99.65 mg/(L^.min) and 2.419 min⁻¹, which are 11.3- and 12.6-fold higher than that of control systems, respectively. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2727, 2019.     

Geochemical processes of iron and manganese in a seasonally stratified lake affected by coal-mining drainage in China

Lake water, pore water, and sediments were sampled in a seasonally stratified lake affected by coal-mining drainage. Contrasting geochemical processes of iron and manganese in summer were investigated by studying the seasonal distributions of iron and manganese species in the water column, pore water, and sediments. The results show that iron buildup in the water during summer was mainly from the gradual dissolution of particulate matter due to the pH decrease, whereas manganese oxide reduction and manganese-bound carbonate dissolution near the sediment–water interface were mainly responsible for manganese accumulation in the stratified hypolimnion. The geochemical processes of iron and manganese in the sediments during early diagenesis were also discussed in terms of the possible influence on the overlying water. Received: November 29, 1999 / Accepted: June 30, 2000     

An analysis of structural similarity in the iron and manganese superoxide dismutases based on known structures and sequences

There are two types of homologous enzymes catalysing the dismutationof the superoxide radical – Cu–Zn superoxide dismutases, and manganese oriron superoxide dismutases. In the latter two forms there is a highpercentage of identity in the primary structures, and the tertiarystructures are very similar particu-larly in the areas of the activesite and in the residues responsible for the formation of the dimer.The quaternary structure of the dimer is also highly conserved.However, it has been found that despite this conservation thereis strong metal ion specificity and many enzymes in the familywill only be active if the correct metal ion is present. The purposeof this study has been to analyse solved X-ray structures forinter-actions common in both the manganese and iron forms andthose that are specific to each, which may indi-cate reasonsfor the metal ion specificity. Initial analysis points to theprobability that it is a combination of a number of residues,and not necessarily the same ones in every instance, which conferthe specificity. In addition we have identified some anomalies inthe currently available Fe/MnSOD structures which may require furtherremodelling and refinement. © Rapid Science 1998     

Iron,zinc and manganese nutrition of wetland rice (Oryza sativa L.) on a gypsum amended sodic soil

A field experiment was conducted to evaluate the effect of three levels of Fe and two levels of Zn, and their combinations, on the growth, yield and Fe, Zn, and Mn nutrition of rice on a zinc deficient sodic soil amended with gypsum. Iron and zinc were supplied as sulphates. Application of Zn significantly enhanced the yield of rice and available soil and plant Zn irrespective of Fe application. Maximum response of rice to Zn was obtained when Fe was applied at the highest rate. While Fe application brought about a significant improvement in available soil and plant Fe and Mn, it decreased significantly Zn content of the crop. After crop harvest, recovery of added Fe was 20% and Zn 12%. Results suggest that benefits of Fe application to rice in sodic soils can only be realised if it is applied along with Zn.     

抗A型产气荚膜梭菌α毒素单链抗体基因的克隆、表达及其生物学活性(英文)

应用RT PCR技术 ,从分泌具有中和活性的抗A型产气荚膜梭菌α毒素单克隆抗体 (McAb)的杂交瘤细胞株 1A8中 ,分别扩增出抗体VH 和VL 基因 ,用linker (Gly4Ser) 3 基因 ,将VH 和VL 基因连接成单链抗体 (ScFv)基因 ,并将其克隆至pGEM T载体中 .经核苷酸序列分析证实 ,VH 和VL 基因及linker基因拼接正确 ,ScFv 1A8基因全长为 72 6bp ,编码2 4 2个氨基酸 ,VH 和VL 基因符合功能性重排的鼠抗体可变区基因特征 ,分别属于鼠免疫球蛋白重链Ⅱ (A)和轻链κⅣ家簇 .将ScFv 1A8基因克隆至表达载体pHOG2 1中 ,构建了重组质粒pHOG 1A8,然后转化至受体菌XL1 BLUE中 ,得到重组菌株XL1 BLUE (pHOG 1A8) .ELISA检测和SDS PAGE分析表明 :经IPTG诱导后所表达的目的蛋白存在于重组菌株XL1 BLUE (pHOG 1A8)的胞周质中 .经薄层扫描分析 :重组菌株XL1 BLUE(pHOG 1A8)的蛋白表达产物占菌体可溶性蛋白的 1 2 % ,其相对分子量约为 31kD .ScFv的生物学活性研究表明 ,ScFv蛋白不但具有中和磷脂酶C的活性 ,而且还能够对致死性腹腔攻击的小鼠产生良好的被动保护作用     

抗A型产气荚膜梭菌α毒素全人源双价单链抗体的构建、表达及其活性的初步研究

目的:为防治A型产气荚膜梭菌α毒素引起的肠毒血症及气性坏疽等相关疾病,构建并高效表达中和α毒素(CPA)的特异性双价单链抗体,并对其生物学活性进行初步研究。方法:以全人源噬菌体抗体库中筛选得到的抗A型产气荚膜梭菌α毒素单链抗体sc Fv基因为模板,PCR的方法扩增两条单链抗体片段并通过引物设计引入中间连接肽G4S或(G4S)3,亚克隆至原核表达载体p ET-28a(+),转化E.coli BL21,IPTG诱导表达、鉴定及表达产物的层析纯化;Western blot和间接ELISA方法检测与抗原的免疫结合活性;通过体外检测抗体抑制CPA水解卵磷脂的活性和溶血活性以及体内小鼠攻毒保护试验初步研究双价单链抗体的生物学活性。结果:双酶切鉴定及基因测序结果表明构建的双价单链抗体sc(Fv)2-5和sc(Fv)2-15均正确,诱导表达后经12%SDS-PAGE分析,两者均以包涵体形式表达且蛋白分子量符合理论值大小,Western blot和间接ELISA分析结果显示,构建的双价单链抗体与抗原CPA具有特异结合活性,且sc(Fv)2-15与抗原的结合活性明显高于sc(Fv)2-5和sc Fv,体外与体内生物活性试验结果进一步证明,sc(Fv)2-15中和毒素的能力较sc(Fv)2-5和sc Fv具有明显优势。结论:成功制备了抗A型产气荚膜梭菌α毒素的全人源双价单链抗体,为进一步研究该毒素引发的各类疾病的诊断和治疗奠定了基础。     

基于数据包络分析方法的辽宁省工业节能减碳效率

以辽宁省2003—2012年39个行业作为独立的决策单元,综合考虑经济、能源和环境效益,结合方向距离函数和径向数据包络分析(DEA)方法对各工业行业节能减碳效率进行测算和分解,核算了各工业行业的CO₂排放,并将CO₂作为一种非期望产出引入到节能减碳效率模型中.结果表明: 研究期间,辽宁省工业行业节能减碳效率具有明显的行业异质性;辽宁省工业节能减碳效率总体不高,但呈现上升趋势;提高纯技术效率和规模效率是提高工业节能减碳效率的主要措施,尤其是提高规模效率.为了提高辽宁省各行业节能减碳效率,辽宁省应加快调整产业结构,鼓励发展低碳排放高效益的产业;提高科技水平,合理调整产业规模;优化能源结构,推进可再生能源和清洁能源的开发.     

NADH-dependent reduction of d-proline in Clostridium sticklandii. Reconstitution from three fractions containing NADH dehydrogenase,d-proline reductase,and a third protein factor

The enzyme system from Clostridium sticklandii catalyzing the NADH-dependent reduction of d-proline was co-purified by chromatography on DEAE-cellulose at pH 8.2 and ammonium sulfate fractionation, and resolved into fractions containing three different protein components, NADH dehydrogenase, d-proline reductase and a third protein factor, by chromatography on DEAE-cellulose at pH 7.0. Upon recombination of the fractions containing the three different protein components, the NADH-dependent reduction of d-proline was successfully reconstituted. The NADH dehydrogenase fractions oxidized NADH in the presence of artificial electron acceptors, and were inhibited by p-hydroxymercuriphenylsulfonate (50% at 80 nM). They contained 3–4 different enzyme bands as revealed by polyacrylamide-gel electropherograms stained with the NADH-dependent reduction of 2,3,5-triphenyltetrazolium chloride. d-Proline reduction was also coupled to a leuco-methylene blue-generating system containing d-glucose and glucose-oxidase (EC 1.1.3.4). Circumstantial evidence indicated that, among the clostridial proteins, only d-proline reductase and the third protein factor were needed for this reaction.Non-standard abbreviations TTC 2,3,5-triphenyltetrazolium chloride     

Investigation of the apparent inefficiency of the coupling between Photosystem II electron transfer and ATP formation

The maximum phosphorylation efficiency achieved with synchronous turnovers of Photosystem II (PS II) in spinach chloroplast lamellae is 0.3 molecules of ATP per pair of electrons transferred. This is the same as the efficiency observed for PS II operating alone in continuous light and would seem to indicate less than 50% coupling efficiency. Flash-induced ATP synthesis associated with both photosystems acting in unison closely approaches twice the flash-induced ATP synthesis associated with the Photosystem-I-dependent oxidation of duroquinol (itself 0.6) and comes close to equalling the highest efficiency observed in steady-state PS I + PS II electron transport. The anomalously low coupling efficiency seen when PS II is operating alone can be overcome by a ΔpH of two units imposed before flash illumination, or by a prior flash series involving the entire electron transfer chain. In contrast, prior electron transport through PS II alone is only slightly effective in enhancing the coupling efficiency of subsequent PS II turnovers. (It should be noted that in all cases where supplementary energy was provided, either by a proton gradient or by prior illumination, this supplementary energy was always below the energetic threshold for phosphorylation. Furthermore, the enhancement of PS II coupling efficiency by supplementary energy persisted even after a large number of subsequent PS II-inducing flashes). The efficiency of flash-induced ATP synthesis associated with whole-chain electron transfer or with PS-I-dependent duroquinol oxidation is also enhanced by the supplementary energy, but only during the first few inefficient flashes, suggesting that in this case the supplementary energy may simply be contributing to the initial build-up of an energetic threshold for ATP synthesis. This cannot be the case when the same supplementary energy contributes to the efficiency of the PS II reaction, since the enhancement then persists for a long time and contributes to an essentially constant flash yield of ATP. Our results imply that during electron transfer involving both photosystems, PS II participates in generating about half of the total ATP, whereas it operates inefficiently only when operating alone. Since hydrogen ions produced by PS I are able to raise the efficiency of subsequent PS-II-dependent phosphorylation, at least some cooperation between the two photosystems takes place and this suggests some donation of protons from PS I to PS II. However, the inability of PS II alone to achieve high efficiency, even with prolonged pre-illumination, would seem to indicate some functional distinction of protons from the two photosystems.