氧化亚铁硫杆菌对金属铜的加工

材料加工的传统技术包括物理方法和化学方法。当今 ,生物技术已进入各个领域 ,也渗透到材料加工领域。因此 ,材料加工技术也包括生物方法。根据加工工件体积变化 ,生物方法加工分为生物去除加工 (Ｒｅｍｏｖａｌ)、生物沉积加工 (Ａｄｄｉｔｉｏｎ)和生物成形加工 (Ｄｅｆｏｒｍａｔｉｏｎ)。研究生物加工方法的最早报导是 1 993年日本冈山大学宇野义幸等人[1～ 3] ,证实了细菌对纯铁、纯铜去除加工的可能性以及附加电场的作用。国内的研究工作进一步证实了生物加工能力 ,并加工出微小齿轮[4～5] 。本文报导氧化亚铁硫杆菌 (Ｔｈｉｏｂａｃ…     

Biomachining: Preservation of Acidithiobacillus ferrooxidans and treatment of the liquid residue

Biomachining has become a promising alternative to micromachining metal pieces, as it is considered more environmentally friendly than their physical and chemical machining counterparts. In this research work, two strategies that contribute to the development of this innovative technology and could promote its industrial implementation were investigated: preservation of biomachining microorganisms (Acidithiobacillus ferrooxidans) for their further use, and making valuable use of the liquid residue obtained following the biomachining process. Regarding the preservation method, freeze‐drying, freezing, and drying were tested to preserve biomachining bacteria, and the effect of different cryoprotectants, storage times, and temperatures was studied. Freezing at –80°C in Eppendorf cryovials using betaine as a cryoprotective agent reported the highest bacteria survival rate (40% of cell recovery) among the studied processes. The treatment of the liquid residue in two successive stages led to the precipitation of most of the total dissolved iron and divalent copper (99.9%). The by‐products obtained (iron and copper hydroxide) could be reused in several industrial applications, thereby enhancing the environmentally friendly nature of the biomachining process.     

Biomachining: metal etching via microorganisms

The use of microorganisms to remove metal from a workpiece is known as biological machining or biomachining, and it has gained in both importance and scientific relevance over the past decade. Conversely to mechanical methods, the use of readily available microorganisms is low-energy consuming, and no thermal damage is caused during biomachining. The performance of this sustainable process is assessed by the material removal rate, and certain parameters have to be controlled for manufacturing the machined part with the desired surface finish. Although the variety of microorganisms is scarce, cell concentration or density plays an important role in the process. There is a need to control the temperature to maintain microorganism activity at its optimum, and a suitable shaking rate provides an efficient contact between the workpiece and the biological medium. The system’s tolerance to the sharp changes in pH is quite limited, and in many cases, an acid medium has to be maintained for effective performance. This process is highly dependent on the type of metal being removed. Consequently, the operating parameters need to be determined on a case-by-case basis. The biomachining time is another variable with a direct impact on the removal rate. This biological technique can be used for machining simple and complex shapes, such as series of linear, circular, and square micropatterns on different metal surfaces. The optimal biomachining process should be fast enough to ensure high production, a smooth and homogenous surface finish and, in sum, a high-quality piece. As a result of the high global demand for micro-components, biomachining provides an effective and sustainable alternative. However, its industrial-scale implementation is still pending.     

Innovative use of Thiobacillus ferrooxidans for the biological machining of metals

Preliminary results on the novel use of the bacterium Thiobacillus ferrooxidans (ATCCJ 3598 and ATCC33020) for the micro‐machining (or biomachinig) of metals are reported. Biomachning is a controlled microbiological process to selectively form microstrucutures on a metal work‐piece by metal removal (or dissolution) using microorganisms. Applying copper and mild steel as work‐pieces, it was shown that the mass removed increased proportionately with machining time. In another experiment, the work‐pieces were coated with organic photo‐resistive materials to mask (i.e. protect) certain regions of the metlas, thereby defining the microstructure to be formed. The unmasked regions were successfully biomachined; the final machined profile was shown to be similar to the coating image on the original metal. Although biomachining proceeded at a slower rate than chemical machining, the undesired leaching of the metal in the region under the masked area (termed undercutting) was not as severely encountered when compared with the latter. This work demonstrates the potential use of microorganisms for the biomachining of metals. As a “green process”, the innovative use of T. ferrooxidans for the micro‐machining of metals opens up the possibility of biomachining as an alternative to conventional metal processing.     

Possibility of biological micromachining used for metal removal

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Combining Fungal Biopesticides and Insecticide-Treated Bednets to Enhance Malaria Control

In developing strategies to control malaria vectors, there is increased interest in biological methods that do not cause instant vector mortality, but have sublethal and lethal effects at different ages and stages in the mosquito life cycle. These techniques, particularly if integrated with other vector control interventions, may produce substantial reductions in malaria transmission due to the total effect of alterations to multiple life history parameters at relevant points in the life-cycle and transmission-cycle of the vector. To quantify this effect, an analytically tractable gonotrophic cycle model of mosquito-malaria interactions is developed that unites existing continuous and discrete feeding cycle approaches. As a case study, the combined use of fungal biopesticides and insecticide treated bednets (ITNs) is considered. Low values of the equilibrium EIR and human prevalence were obtained when fungal biopesticides and ITNs were combined, even for scenarios where each intervention acting alone had relatively little impact. The effect of the combined interventions on the equilibrium EIR was at least as strong as the multiplicative effect of both interventions. For scenarios representing difficult conditions for malaria control, due to high transmission intensity and widespread insecticide resistance, the effect of the combined interventions on the equilibrium EIR was greater than the multiplicative effect, as a result of synergistic interactions between the interventions. Fungal biopesticide application was found to be most effective when ITN coverage was high, producing significant reductions in equilibrium prevalence for low levels of biopesticide coverage. By incorporating biological mechanisms relevant to vectorial capacity, continuous-time vector population models can increase their applicability to integrated vector management.     

Effects of Fe deficiency on the protein profile of Brassica napus phloem sap

The aim of this work was to study the effect of Fe deficiency on the protein profile of phloem sap exudates from Brassica napus using 2DE (IEF‐SDS‐PAGE). The experiment was repeated thrice and two technical replicates per treatment were done. Phloem sap purity was assessed by measuring sugar concentrations. Two hundred sixty‐three spots were consistently detected and 15.6% (41) of them showed significant changes in relative abundance (22 decreasing and 19 increasing) as a result of Fe deficiency. Among them, 85% (35 spots), were unambiguously identified. Functional categories containing the largest number of protein species showing changes as a consequence of Fe deficiency were signaling and regulation (32%), and stress and redox homeostasis (17%). The Phloem sap showed a higher oxidative stress and significant changes in the hormonal profile as a result of Fe deficiency. Results indicate that Fe deficiency elicits major changes in signaling pathways involving Ca and hormones, which are generally associated with flowering and developmental processes, causes an alteration in ROS homeostasis processes, and induces decreases in the abundances of proteins involved in sieve element repair, suggesting that Fe‐deficient plants may have an impaired capacity to heal sieve elements upon injury.     

Antioxidant properties of rimantadine in influenza virus infected mice and in some model systems

Influenza virus infection is associated with development of oxidative stress in lung and blood plasma, viz. increase of primary and secondary lipid peroxidation products. It was established that rimantadine treatment led to a decrease of the products of lipid peroxidation in tissues of mice experimentally infected with influenza virus A/Aichi/2/68 (H3N2). The effect is strongest in blood plasma (a decrease of about 50%) and weaker in the lung (about 20%). To elucidate the mechanism of this action of rimantadine, experiments were carried out with some model systems. The capability of rimantadine to scavenge superoxide radicals (scavenging properties) was studied in a system of xanthine-xanthine oxidase to generate superoxide. The amount of superoxide was measured spectrophotometrically by the NBT-test and chemiluminesce. Rimantadine does not show scavenging properties and its antioxidant effect observed in vivo, is not a result of its direct action on the processes of lipid peroxidation and/or interaction with antioxidant enzymes. The antioxidant properties of rimantadine were investigated by measurement of induced lipid peroxidation in a Fe2+ and (Fe2+ - EDTA) system with an egg liposomal suspension. Our findings with model systems do not prove an antioxidant or prooxidant effect of the drug on the processes of lipid peroxidation. Apparently, the observed antioxidant effect of rimantadine in vivo is not connected directly with free radical processes in the organism.     

Effects of manganese (Mn++) and iron (Fe+++) on magnetic resonance imaging (MRI) characteristics of human placenta and amniotic fluid

The contrast and intensity of a magnetic resonance image (MRI) is affected in part by the spin-lattice relaxation time (T1) and spin-spin relaxation time (T2). Certain paramagnetic metal ions can alter these parameters suggesting that they may be useful contrast agents in MRI. In this study, Mn++ and Fe+++ were examined for their effects on T1 and T2 in human placenta and amniotic fluid (AF) at concentrations between 0.002 and 2.0 mM. Both Mn++ and Fe+++ produced a dose-dependent decrease in placental and AF T1. The effects of Fe+++ were not pronounced, decreasing T1 only at the highest concentrations, and not to the same degree as Mn++. Placental T2 was also significantly decreased by Mn++, whereas Fe+++ had no effect. These differences may be due to molecular binding, uptake by the placenta, or the paramagnetic characteristics of the metals. The results suggest that Mn++ will alter human placental MRI for T1 and to a lesser extent T2-dependent imaging processes. Fe+++ should have little or no effect on human placental MRI, except at very high concentrations.     

The influence of light and nutrient addition upon the sediment chemistry of iron in an arctic lake

The geochemical response of sediments to increased nutrient input to an Alaskan, arctic lake was examined using direct measurements of sediment-water chemical fluxes. An unexpected increase in Fe flux occurred when sediments were exposed to high incident radiation and nutrient concentrations. Correlation between light and acid-soluble Fe concentrations suggests that photoreduction of Fe(III) oxides may occur, but nutrient addition enhanced the effect indicating that primary productivity was also important. The processes controlling the flux of Fe from sediments in this lake were complex and included the redox potential (dissolved oxygen concentration) of the water, quality of organic matter present in the sediment, light, and nutrients supplied from the sediments and/or water column. These four factors together with the possibility of direct uptake of Fe by phytoplankton and the possible release of algal reductants may contribute to Fe cycling in this lake.     

The influence of alpha-tocopherol and pyritinol on oxidative DNA damage and lipid peroxidation in human lymphocytes

Unscheduled DNA synthesis (UDS) and lipid peroxidation (LPO) were measured in human peripheral lymphocytes from healthy volunteers. These processes were induced by the catalytic system Fe2+-sodium ascorbate. The degree of induced LPO was measured spectrophotometrically by the thiobarbituric acid assay. UDS was detected by scintillometric measurement of the incorporation of 3H-thymidine into DNA. The protective action by fat-soluble vitamin E (D,L-alpha-tocopherol) and the artificial antioxidant pyritinol on UDS and LPO was also investigated. The system Fe2+ (2 mumole/l)-sodium ascorbate (30 mumole/l) increased the LPO level in healthy volunteers approximately 2.5 times and the incorporation of 3H-thymidine by 60-70%. alpha-Tocopherol (0.2 mmole/l) very efficiently suppressed LPO processes (p less than 0.01) and the oxidative damage of DNA measured as UDS was also significantly diminished (p less than 0.05). Pyritinol had no effect on LPO and UDS under our experimental conditions.     

Interaction of Trace Elements and Ligninolytic Enzymes in <Emphasis Type="Italic">Pleurotus eryngii</Emphasis>

Considering the fact that some trace elements have influence on the growth and physiological processes in the fungi, the aim of this study was to resolve the question of whether Fe, Zn, and Se, added to the medium in the different forms, affect activity of selected Pleurotus eryngii ligninolytic enzymes participating in mandarine peels submerged fermentation. Compared with the control, Fe and Zn showed stimulatory effect on laccase activity. Reduction in the activity was emphasized with cultivation time, but it was slower in the presence of Zn than in the presence of Fe. Among studied Se forms, SeO₂ was the most unfavorable Se source for laccase activity. All tested trace elements, independent on form, showed stimulatory effect on the activity of Mn-oxidizing peroxidases on the seventh day of cultivation. Based on the results, it could be concluded that the presence of the tested trace elements can advance various biotechnological processes among which is biodegradation of agricultural wastes, potential environmental pollutants.     

The effect of desferrioxamine and ferric ammonium citrate on the uptake of iron by the membrane iron-binding component of human melanoma cells.

The effect of ferric ammonium citrate (FAC) and desferrioxamine (DFO) on membrane iron and transferrin uptake have been investigated using SK-MEL-28 human melanoma cells which express the membrane-bound transferrin homologue, melanotransferrin, at high concentrations. Exposure of melanoma cells to DFO increased membrane non-Tf-bound Fe uptake (putative melanotransferrin Fe-binding sites), suggesting upregulation of the membrane Fe-binding component. However, exposure to FAC did not result in down-regulation. Indeed, an increase in non-Tf-bound membrane Fe was apparent. Results suggested that non-Tf-bound membrane Fe uptake occurred by two processes corresponding to the specific and non-specific mechanisms of Fe uptake from Tf described previously (Richardson, D.R. and Baker, E. (1990) Biochim. Biophys. Acta 1053, 1-12).     

Prediction of reducible soil iron content from iron extraction data

Soils contain various iron compounds that differ in solubility, reducibility and extractability. Moreover, the contribution of the various iron compounds to total iron (Fe) and total Fe concentrations differs highly among soils. As a result, the total reducible Fe content can also differ among soils, and so does the dynamics of iron reduction. These factors complicate the prediction of reducible Fe based on Fe extraction data and hamper the application of process-based models for reduced or waterlogged soils where redox processes play a key-role. This paper presents a theoretical analysis relating reducible to extractable Fe reported in the literature. Predictions made from this theoretical analysis were evaluated in soil incubations using 18 rice paddy soils from all over the world. The incubation studies and the literature study both show that reducible Fe can be related to Fe from some selected, but not all, iron extractions. The combination of measurements for labile Fe(III)oxides (derived from oxalate-extractable Fe) and stabile Fe(III)oxides (derived from dithionite-citrate-extractable Fe) shows highly significant correlations with reducible Fe with high coefficients of determination (r² = 0.92–0.95 depending on the definition of stabile Fe(III)oxides). Given the high diversity in rice soils used for the incubations, these regression equations will have general applicability. Application of these regression equations in combination with soil database information may improve the predictive ability of process-based models where soil redox processes are important, such as CH₄ emission models derived for rice paddies or wetlands.     

Effect of lecithin on liver microsomal lipid peroxidation]

The effect of exogeneous (egg) lecithin on peroxidation of microsomal lipids was studied with the view of elucidating the role of various components of lipid substrate in the overall oxidation rate of the lipids. The following processes were studied a) NADPH-dependent microsomal lipid peroxidation in the presence of lecithin; b) ascorbate-dependent microsomal lipid peroxidation in the presence of lecithin; c) oxidation of lipid mixture, isolated from the microsomes, and that of lecithin in the presence of the Fe2+ + ascorbate system; 4) oxidation of lecithin induced by the Fe2+ + ascorbate system. It was found that in the presence of exogeneous lecithin the oxidation of microsomal lipids in inhibited, which is probably due to the peculiarities of lecithin oxidation. It was shown that the specific rate of lecithin oxidation is decreased with an increase in lecithin concentration. Possible mechanisms of lecithin effect on microsomal lipid peroxidation are discussed.     

Iron–sulfur cluster biosynthesis in photosynthetic organisms

Iron–sulfur (Fe/S) cluster containing proteins are widely distributed in nature and are involved in numerous processes including electron transfer, metabolic reactions, sensing, signaling, and regulation of gene expression. The knowledge about the biogenesis of Fe/S clusters, and the assembly and maturation of Fe/S cluster containing proteins is still limited, especially in photosynthetic organisms. In most organisms analyzed so far the biogenesis of Fe/S clusters involves more than one machinery. The additional compartment in photoautotrophic organisms, the plastids, presents an additional challenge for the regulation of Fe/S cluster biogenesis. The requirement for Fe/S proteins in multiple chloroplast processes argues that Fe/S cluster assembly is an essential part of plastid functionality. This review focuses on the interesting and unique aspects of Fe/S cluster biogenesis in photosynthetic organisms and compares them to what is known in other organisms.     

Astaxanthin and peridinin inhibit oxidative damage in Fe(2+)-loaded liposomes: scavenging oxyradicals or changing membrane permeability?

Astaxanthin and peridinin, two typical carotenoids of marine microalgae, and lycopene were incorporated in phosphatidylcholine multilamellar liposomes and tested as inhibitors of lipid oxidation. Contrarily to peridinin results, astaxanthin strongly reduced lipid damage when the lipoperoxidation promoters-H(2)O(2), tert-butyl hydroperoxide (t-ButOOH) or ascorbate-and Fe(2+):EDTA were added simultaneously to the liposomes. In order to check if the antioxidant activity of carotenoids was also related to their effect on membrane permeability, the peroxidation processes were initiated by adding the promoters to Fe(2+)-loaded liposomes (encapsulated in the inner aqueous solution). Despite that the rigidifying effect of carotenoids in membranes was not directly measured here, peridinin probably has decreased membrane permeability to initiators (t-ButOOH > ascorbate > H(2)O(2)) since its incorporation limited oxidative damage on iron-liposomes. On the other hand, the antioxidant activity of astaxanthin in iron-containing vesicles might be derived from its known rigidifying effect and the inherent scavenging ability.     

Competition of Fe(III) reduction and methanogenesis in an acidic fen

Peatlands are sources of relevant greenhouse gases such as CH4, but the temporal presence of Fe(III) may inhibit methanogenesis. Because excess of carbon during the vegetation period might allow concomitant electron-accepting processes, Fe(III) reduction and methanogenesis were studied during an annual season in an acidic fen. The upper peat layer displayed the highest Fe(II)- and CH4-forming activities. The rates of Fe(II) formation did not change during the year and methanogenesis started mostly when Fe(II) formation reached a plateau. Most of the Fe(III) pool seemed to be bioavailable, and addition of nitrilotriacetic acid stimulated only light Fe(II) formation, whereas EDTA and anthraquinone-2,6-disulfonate had no effect. In the presence of an inhibitor for methanogenesis (sodium 2-bromoethanesulfonate), Fe(II) formation was inhibited to 45%. Addition of Fe(III) during ongoing methanogenesis led only to a partial inhibition of CH4 formation. The proportion of acetoclastic methanogenesis varied between 42% and 90%, but no trend with time was observed. The number of acetate-, ethanol- or lactate-utilizing Fe(III) reducers approximated 10(5)-10(6) cells g (fresh wt peat)(-1). Fermentative glucose-utilizing Fe(III)-reducers were most abundant. Our results suggest that (1) methanogens used Fe(III) as an electron acceptor and (2) fermenting bacteria, which do not compete with methanogens for common electron donors, dominated the reduction of Fe(III) in this fen.     

The mechanism of cobalt toxicity in mung beans

The effects of cobalt on the growth and nutrient balance of mung beans were investigated. Inhibition of seedling growth occurred at 5 μ M Co and was associated with chlorosis of the younger leaves. Analysis of nutrient concentrations in root and leaf tissue of mung beans treated with 5 μ M Co showed that none of the macronutrients and only two of the micronutrients, Mn and Fe, were significantly affected. The Mn concentration in roots was reduced by 55% and the Fe concentration in the leaves by 80%. Uptake of Fe into roots was not inhibited by Co but transport of Fe to the shoot was greatly reduced. It was shown that the effect of Co on growth was additive to that of Fe deficiency, which argues against Co-induced Fe deficiency as the primary cause of growth inhibition by Co. Rather, it was considered that the high concentrations of Co in the roots and leaves compared with essential micronutrient cations can disrupt a range of metabolic processes due to competitive interactions. Comparison of the toxic effects of Co with those of other toxic trace metals Cd, Cu, Ni and Hg showed that at an applied concentration of 5 μ M , there were obvious differences in both the visual symptoms and in nutrient concentrations. The main difference between Co and the other metals was that only Co stimulated the uptake of S into the plant and its transport to the shoots, where the S concentration in the leaves was increased 2-fold. The common feature of all the trace metals examined was the strong inhibition of Fe transport to the shoot. A possible mechanism for the interaction of other trace metals with Fe transport is discussed.