Diatom Frustules Decorated with Co Nanoparticles for the Advanced Anode of Li-Ion Batteries.

Silica is regarded as a promising anode material for lithium-ion batteries (LIBs) because of its high theoretical capacity. However, large volume variation and poor electrical conductivity are limiting factors for the development of SiO2 anode materials. To solve this problem, combining SiO2 with a conductive phase and designing hollow porous structures are effective ways. In this work, The Co(II)-EDTA chelate on the surface of diatom biosilica (DBS) frustules and obtained DBS@C-Co composites decorated with Co nanoparticles by calcination without a reducing atmosphere is first precipitated. The unique three-dimensional structure of diatom frustules provides enough space for the volume change of silica during lithiation/delithiation. Co nanoparticles effectively improve the electrical conductivity and electrochemical activity of silica. Through the synergistic effect of the hollow porous structure, carbon layer and Co nanoparticles, the DBS@C-Co-60 composite delivers a high reversible capacity of >620 mAh g-1 at 100 mA g-1 after 270 cycles. This study provides a new method for the synthesis of metal/silica composites and an opportunity for the development of natural resources as advanced active materials for LIBs.

Enhancement Mechanism of Stibnite Dissolution Mediated by Acidithiobacillus ferrooxidans under Extremely Acidic Condition.

Oxidative dissolution of stibnite (Sb2S3), one of the most prevalent geochemical processes for antimony (Sb) release, can be promoted by Sb-oxidizing microbes, which were studied under alkaline and neutral conditions but rarely under acidic conditions. This work is dedicated to unraveling the enhancement mechanism of stibnite dissolution by typical acidophile Acidithiobacillus ferrooxidans under extremely acidic conditions. The results of solution behavior showed that the dissolution of Sb2S3 was significantly enhanced by A. ferrooxidans, with lower pH and higher redox potential values and higher [Sb(III)] and [Sb(V)] than the sterile control. The surface morphology results showed that the cells adsorbed onto the mineral surface and formed biofilms. Much more filamentous secondary minerals were formed for the case with A. ferrooxidans. Further mineral phase compositions and Sb/S speciation transformation analyses showed that more secondary products Sb2O3/SbO2-, Sb2O5/SbO3-, SO42-, as well as intermediates, such as S0, S2O32- were formed for the biotic case, indicating that the dissolution of Sb2S3 and the Sb/S speciation transformation was promoted by A. ferrooxidans. These results were further clarified by the comparative transcriptome analysis. This work demonstrated that through the interaction with Sb2S3, A. ferrooxidans promotes S/Sb oxidation, so as to enhance S/Sb transformation and thus the dissolution of Sb2S3.

The differential inhibitive effects and fates of As(III) and As(V) mediated by Sulfobacillus thermosulfidooxidans grown on S0, Fe2+ and FeS2.

Arsenic often coexists with metal sulfide minerals and occurs in different speciation and different toxicity in responding to Fe/S biooxidation. The differential inhibitive effects and fates of As(III) and As(V) during biooxidations of elemental sulfur (S0), ferrous ions (Fe2+) and pyrite (FeS2) by Sulfobacillus thermosulfidooxidans were studied. The results revealed that the arsenic species hardly changed for the biooxidation of S0, but dramatically changed for the biooxidation of Fe2+ and FeS2. Different transformation degree between As(III) and As(V) occurred for biooxidation of FeS2 in the presence of arsenic, where about 72% of As(III) was transformed to As(V) for the group with As(III) added, and 16% of As(V) was transformed to As(III) for that with As(V) added. Both formation and dissolution of amorphous ferric arsenate occurred during biooxidation of FeS2 with the addition of As(III) or As(V) and for the group grown on Fe2+ with added As(V), which were controlled by the changes of Fe/As molar ratio and pH value in the solution. Jarosite was detected for the group grown on Fe2+ and could adsorb As(III) and As(V). The inhibitive effects of As(V) were higher than As(III) when the strain grew on FeS2, which was contrary to those when the strain grew on S0 and Fe2+. The above results signify that the fates and inhibitive effects of arsenic are much related to each other, and such a relationship is significantly affected by the utilization of Fe/S energy substrates by the sulfur- and ferrous-oxidizing microorganisms.

Biogenic FeS promotes dechlorination and thus de-cytotoxity of trichloroethylene.

Abiotic iron monosulfide (FeS) has attracted growing interests in dechlorinating trichloroethylene (TCE) in anoxic groundwater, but it is still unclear how biogenic FeS affects the dechlorination and thus the cytotoxity of TCE. In this work, a biogenic FeS was synthesized by Shewanella oneidensis MR-1 with addition of ferrihydrite and S0, and it was used for dechlorination of TCE in alkaline environment and the de-cytotoxicity was evaluated by the growth of Synechocystis sp. PCC6803. The results show that the biogenic FeS was of mackinawite, with a loose flower-like mosaic structure. The dechlorination of TCE by the biogenic FeS was accelerated by 6 times than that by abiotic FeS. TCE was dechlorinated mainly by hydrogenolysis to form dichloroethane (C2H2Cl2), vinyl chloride (C2H3Cl), and finally ethylene, accompanied with transformation of both Fe2+ to Fe3+ and monosulfide to disulfide and polysulfide on the biogenic FeS surface. The concentration for 50% of maximal inhibition effect (EC50) of TCE to Synechocystis was 486 mg/L and the inhibition to Synechocystis under the EC50 was relieved more significantly on addition of the biogenic FeS than that of abiotic FeS. These results indicate that the biogenic FeS promoted the dechlorination and thus de-cytotoxity of TCE.

Evidence of cell surface iron speciation of acidophilic iron-oxidizing microorganisms in indirect bioleaching process.

While indirect model has been widely accepted in bioleaching, but the evidence of cell surface iron speciation has not been reported. In the present work the iron speciation on the cell surfaces of four typically acidophilic iron-oxidizing microorganism (mesophilic Acidithiobacillus ferrooxidans ATCC 23270, moderately thermophilic Leptospirillum ferriphilum YSK and Sulfobacillus thermosulfidooxidans St, and extremely thermophilic Acidianus manzaensis YN25) grown on different energy substrates (chalcopyrite, pyrite, ferrous sulfate and elemental sulfur (S(0))) were studied in situ firstly by using synchrotron-based micro- X-ray fluorescence analysis and X-ray absorption near-edge structure spectroscopy. Results showed that the cells grown on iron-containing substrates had apparently higher surface iron content than the cells grown on S(0). Both ferrous iron and ferric iron were detected on the cell surface of all tested AIOMs, and the Fe(II)/Fe(III) ratios of the same microorganism were affected by different energy substrates. The iron distribution and bonding state of single cell of A. manzaensis were then studied in situ by scanning transmission soft X-ray microscopy based on dual-energy contrast analysis and stack analysis. Results showed that the iron species distributed evenly on the cell surface and bonded with amino, carboxyl and hydroxyl groups.

Saccharification of orange peel wastes with crude enzymes from new isolated Aspergillus japonicus PJ01.

This study investigated the saccharification of orange peel wastes with crude enzymes from Aspergillus japonicus PJ01. Pretreated orange peel powder was hydrolyzed by submerged fermentation (SmF) and solid-state fermentation (SSF) crude enzymes, the results showed that 4 % (w/v) of solid loading, undiluted crude enzymes, and 45 °C were suitable saccharification conditions. The hydrolysis kinetics showed that the apparent Michaelis-Menten constant [Formula: see text] and maximal reaction rate [Formula: see text] were 73.32 g/L and 0.118 g/(L min) for SmF enzyme, and 41.45 g/L and 0.116 g/(L min) for SSF enzyme, respectively. After 48 h of hydrolysis, the saccharification yields were 58.5 and 78.7 %, the reducing sugar concentrations were 14.9 and 20.1 mg/mL by SmF and SSF enzymes. Material balance showed that the SmF enzymatic hydrolysate was enriched galacturonic acid > arabinose > galactose > xylose, and the SSF enzymatic hydrolysate was enriched galacturonic acid > xylose > galactose > arabinose.

Differential expression of extracellular thiol groups of moderately thermophilic Sulfobacillus thermosulfidooxidans and extremely thermophilic Acidianus manzaensis grown on S(0) and Fe (2.).

Bio-oxidation of elemental sulfur (S(0)) is very important in bioleaching and sulfur cycle. S(0) was proposed to be first activated by reacting with reactive thiol groups (-SH) of outer membrane proteins, forming -S n H (n ≥ 2) complexes. The differential expression of -SH of moderately thermophilic Sulfobacillus thermosulfidooxidans and extremely thermophilic Acidianus manzaensis grown on Fe(2+) and S(0) was investigated by synchrotron radiation-based scanning transmission X-ray microscopy (STXM) imaging and micro-beam X-ray fluorescence (µ-XRF) mapping. The STXM imaging and µ-XRF mapping of extracellular -SH were based on the analysis of Ca(2+) bound on the cell. By comparing Ca(2+) of the cells with and without labeling by Ca(2+), the distribution and content of thiol groups were obtained. The results showed that, for both S. thermosulfidooxidans and A. manzaensis, the expression of extracellular -SH of S(0)-grown cells was higher than that of Fe(2+)-grown cells. Statistical analysis indicated that the expression of extracellular -SH for S. thermosulfidooxidans and A. manzaensis grown on S(0) was 2.37 times and 2.14 times, respectively, to that on Fe(2+). These results evidently demonstrate that the extracellular thiol groups are most probably involved in elemental sulfur activation and oxidation of the acidophilic sulfur-oxidizing microorganisms.

Comparative study of multi-enzyme production from typical agro-industrial residues and ultrasound-assisted extraction of crude enzyme in fermentation with Aspergillus japonicus PJ01.

Submerged fermentation (SmF) and solid-state fermentation (SSF) of Aspergillus japonicus PJ01 for multi-enzyme complexes (MEC) production were comparatively studied. The results showed that orange peel and wheat bran were the best substrates for MEC production in SmF and SSF, respectively. After 72 h of cultivation under SmF, the maximal pectinase, CMCase, and xylanase activities reached 2610, 85, and 335 U/gds (units/gram dry substrate), respectively; while after 72 h of cultivation under SSF, these three enzymes' activities reached 966, 58, and 1004 U/gds, respectively. Effects of ultrasound on extraction of crude enzymes from SSF medium were determined, the maximal activities of pectinase, CMCase, and xylanase increased to 1.20, 1.48, and 1.30-fold, respectively. Apparent different mycelia growths of SSF and SmF were observed by scanning electron microscopy; and different isoforms of the crude enzyme extracts from SSF and SmF were presented by zymogram analysis.

The effect of iron on growth, lipid accumulation, and gene expression profile of the freshwater microalga Chlorella sorokiniana.

The effects of iron on the growth, lipid accumulation, and gene expression profiles of the limnetic Chlorella sorokiniana CCTCC M209220 under photoautotrophy were investigated. The addition of iron up to 10(-5) mol l(-l) increased final cell densities by nearly 2-fold at 2.3 × 10(7) cells/ml, growth rate by 2-fold, and the length of the exponential phase by 5 days as compared to unsupplemented controls while 10(-3) mol l(-1) iron was toxic. The lipid content increased from 12 % for unsupplemented cultures to 33 % at 10(-4) mol l(-1) iron while the highest overall lipid yield reached 179 mg l(-1). A genefishing and qPCR comparison between the C. sorokiniana at low and high iron levels indicated increases in the expression of several genes, including carbonic anhydrase involved in microalgal cell growth, as well as acc1 and choline transporter related to lipid synthesis. This study provides insights into changes in gene expression and metabolism that accompany iron supplementation to Chlorella as well as potential metabolic engineering targets for improving growth and lipid synthesis in microalgae.

Developing a novel lithium-ion battery anode material via thiol functionalization of diatom frustules plus Ag modification.

The biosilicification of diatoms allows for the customization of the synthesis of functionalized diatom frustules. The S active sites (-SH) on diatom frustules were created by adding the organic silicon sources tetramethoxysilane (TMOS) and (3-mercaptopropyl)trimethoxysilane (MPTMS). The mechanisms of adsorption-reduction and the indirect effects of S active sites on electrochemical performance were declared. The DBS@C-Ag-3 anode material sourced from the cultivation condition with a silicon source of TMOS:MPTMS = 3:1 shows the best comprehensive performance and delivers a discharge capacity of ∼660 mAh·g-1 after 1000 cycles at 1 A·g-1. The electrochemical performance of DBS@C-Ag anode materials is also found to be dominated by structure at high temperatures and conductivity at low temperatures. Such a diatom frustule structure with sulfhydryl functionalization is promising for anode materials, and it suggests a biological strategy for creating other electrode materials by modifying them with metals to improve electrochemical performances.

Fe/S Redox-Coupled Mercury Transformation Mediated by Acidithiobacillus ferrooxidans ATCC 23270 under Aerobic and/or Anaerobic Conditions.

Bioleaching processes or microbially mediated iron/sulfur redox processes in acid mine drainage (AMD) result in mineral dissolution and transformation, the release of mercury and other heavy metal ions, and changes in the occurrence forms and concentration of mercury. However, pertinent studies on these processes are scarce. Therefore, in this work, the Fe/S redox-coupled mercury transformation mediated by Acidithiobacillus ferrooxidans ATCC 23270 under aerobic and/or anaerobic conditions was studied by combining analyses of solution behavior (pH, redox potential, and Fe/S/Hg ion concentrations), the surface morphology and elemental composition of the solid substrate residue, the Fe/S/Hg speciation transformation, and bacterial transcriptomics. It was found that: (1) the presence of Hg2+ significantly inhibited the apparent iron/sulfur redox process; (2) the addition of Hg2+ caused a significant change in the composition of bacterial surface compounds and elements such as C, N, S, and Fe; (3) Hg mainly occurred in the form of Hg0, HgS, and HgSO4 in the solid substrate residues; and (4) the expression of mercury-resistant genes was higher in earlier stages of growth than in the later stages of growth. The results indicate that the addition of Hg2+ significantly affected the iron/sulfur redox process mediated by A. ferrooxidans ATCC 23270 under aerobic, anaerobic, and coupled aerobic-anaerobic conditions, which further promoted Hg transformation. This work is of great significance for the treatment and remediation of mercury pollution in heavy metal-polluted areas.

Biosynthesis and Detection of Domoic Acid from Diatom Pseudo-nitzschia: A Review.

The domoic acid (DA) produced by certain species of the marine pennate diatom genus Pseudo-nitzschia is highly neurotoxic and can induce nerve excitability and neurotoxicity by binding with ionotropic glutamate receptors, causing amnesic shellfish poisoning in humans who consume seafood contaminated with DA. In recent years, poisoning of humans caused by DA has occurred around the world, which has attracted increasing attention, and studies on DA production by Pseudo-nitzschia have become the hotpot. This article reviews the progress in the biosynthesis of DA by the typical diatom Pseudo-nitzschia, in which the metabolic pathway of the biosynthesis of DA and its precursors, i.e., geranyl pyrophosphate and L-glutamate, and the various environmental factors affecting DA production including temperature, light intensity, nutrients, trace metals, and alien bacteria are discussed. The detection methods of DA (including bioassays, enzyme linked immunosorbent assays, high performance liquid chromatography, capillary electrophoresis and biosensors), as well as the morphology and toxigenicity of Pseudo-nitzschia are also presented.

Effects of Eggshell Thickness, Calcium Content, and Number of Pores in Erosion Craters on Hatching Rate of Chinese Alligator Eggs.

The Chinese alligator (Alligator sinensis), found only in a small region in southeastern Anhui Province, is listed as critically endangered (CR) by the International Union for Conservation of Nature (IUCN) due to its current declining population trend. Any abnormalities in the physical properties of an egg can decrease the hatching rate. In particular, eggshells play an essential role in embryo development, motivating us to analyze the microstructures of the eggshells of Chinese alligators. In this study, we categorized the eggshells into two groups, based on the hatching rates, and analyzed the relationship between the eggshell parameters (eggshell thickness, calcium content, and number of pores in erosion craters) and the hatching rate, as well as the relationships between the eggshell parameters. We found that the shells of the eggs with high hatching rates were thicker than those of the eggs with low hatching rates. There were also fewer erosion-crater pores on the surfaces of the eggs with high hatching rates than on the surfaces of the eggs with low hatching rates. Moreover, the shell Ca content was significantly higher in the eggs with high hatching rates than in the eggs with low hatching rates. Cluster modeling indicated that the highest hatching rate occurred when the eggshell thickness was 200-380 µm and there were 1-12 pores. These results suggest that eggs with adequate Ca contents, thicker shells, and less air permeability are more likely to hatch. Furthermore, our findings can inform future studies, which will be vital for the survival of the critically endangered Chinese alligator species.

Physiological evaluation of a new Chlorella sorokiniana isolate for its biomass production and lipid accumulation in photoautotrophic and heterotrophic cultures.

A novel green unicellular microalgal isolate from the freshwater of the Inner Mongolia Province of China and named as CCTCC M209220, grows between pH 6 and 11 and temperatures of 20-35°C with optimal conditions at pH 9 and 30°C. Morphological features and the phylogenetic analysis for the 18S rRNA gene reveal that the isolate is a Chlorella sorokiniana strain. A nitrogen source test reveals that this strain can grow well with nitrate and urea, but not ammonium. The strain can grow heterotrophically with glucose as the carbon source and accumulates lipid content as high as 56% (w/w) dry weight after 7 days in high glucose concentrations compared to 19% lipids achieved in 30 days of photoautotrophic culture. The relative neutral lipid content as a fraction of the total lipid is also much higher in heterotrophic culture as compared to photoautotrophic culture.

The Transformation of Hg2+ during Anaerobic S0 Reduction by an AMD Environmental Enrichment Culture.

Mercury (Hg) is a highly toxic and persistent heavy metal pollutant. The acid mine drainage (AMD) environment in sulfide-mining areas is a typical Hg pollution source. In this paper, the transformation of Hg2+ during anaerobic S0 reduction by an AMD environmental enrichment culture was studied by multiple spectroscopic and microscopic techniques. The experimental results showed that the microbial S0 reduction of the AMD enrichment culture was significantly inhibited in the presence of Hg2+. The results of cell surface morphology and composition analysis showed that there was obvious aggregation of flocculent particles on the cell surface in the presence of Hg2+, and the components of extracellular polymeric substances on the cell surface changed significantly. The results of surface morphology and C/S/Hg speciation transformation analyses of the solid particulate showed that Hg2+ gradually transformed to mercuric sulfide and Hg0 under anaerobic S0 reduction by the AMD enrichment culture. The microbial community structure results showed that Hg2+ significantly changed the enrichment community structure by decreasing their evenness. The dominant microorganisms with S0 reduction functions are closely related to mercury transformation and are the key driving force for the transformation of substrate solid particulate and cellular substances, as well as the fixation of Hg2+.

Release and fate of As mobilized via bio-oxidation of arsenopyrite in acid mine drainage: Importance of As/Fe/S speciation and As(III) immobilization.

Mining activities expose sulfidic minerals including arsenopyrite (FeAsS) to acid mine drainage (AMD). The subsequent release of toxic arsenic (As) can have great negative implications for the environment and human health. This study investigated the evolution of secondary products and As speciation transformations during arsenopyrite bio-oxidation in AMD collected from a polymetallic mine. Immobilization of the As solubilized via arsenopyrite bio-oxidation using red mud (RM) was also studied. The results show that the high ionic strength (concentrations of dissolved Fe3+, SO42-, and Ca2+ reached values up to 0.75, 3.38, and 0.35 g/L, respectively) and redox potential (up to +621 mV) of AMD (caused primarily by Fe3+) enhanced the dissolution of arsenopyrite. A high [Fe]aq/[As]aq ratio in the AMD favored the precipitation of tooeleite during arsenopyrite bio-oxidation, and the formation of other poorly crystalline products such as schwertmannite and amorphous ferric arsenate also contributed to As immobilization. Bacterial cells served as important nucleation sites for the precipitation of mineral phases. Arsenopyrite completely dissolved after 12 days of bio-oxidation in AMD and the [As]aq (mainly present as As(III)) reached 1.92 g/L, while a greater [As]aq was observed in a basal salts medium (BSM) assay (reaching 3.02 g/L). An RM addition significantly promoted As(III) immobilization, with final [As(III)]aq decreasing to 0.16 and 1.43 g/L in AMD and BSM assays respectively. No oxidation of As(III) was detected during the immobilization process. These findings can help predict As release from arsenopyrite on contact with AMD and, on a broader scale, assist in designing remediation and treatment strategies to mitigate As contamination in mining.

Highly-efficient and sequential recovery of rare earth elements, alumina and silica from coal fly ash via a novel recyclable ZnO sinter method.

A novel sinter method using ZnO as the activator instead of the conventional Na2CO3/CaCO3, (NH4)2SO4, and K2S2O7 was developed to achieve efficient sequential extraction of rare earth elements (REEs), alumina (Al), and silica (Si) from coal fly ash (CFA). Up to 93.3% Si, 87.1% REEs (70.7% Ce, 82.5% La, 83.2% Gd, 87.1% Nd, 62.3% Dy, and 81.7% Y), and 92.9% Al were extracted from CFA, respectively. Moreover, 93.1% of the ZnO activator was efficiently recycled, and the yield of red mud was only 14.9%. X-ray diffraction (XRD) and X-ray absorption near edge structure (XANES) results showed that the speciation transformation of Al/Si during CFA/ZnO roasting was as follows: mullite, quartz, amorphous Al2O3, and SiO2 → Zn0.75Al1.5Si1.5O6, kyanite and willemite → gahnite and quartz/cristobalite solid solutions. The change in the REEs occurrence mode hinted at the migration of most REEs in aluminosilicates forms with Si during roasting, and disassociation with Si into the acid-soluble form after alkali leaching. These results indicate that the coupling of Al-Si-REE in CF was broken by this ZnO sinter method, promoting the sequential and efficient extraction of REEs, Al, and Si from CFA. This study provides a green and efficient strategy for element recovery from CFA, substantially reducing residues and favoring REEs concentration.

Efficient dealkalization of red mud and recovery of valuable metals by a sulfur-oxidizing bacterium.

Red mud (RM) is a highly alkaline polymetallic waste generated via the Bayer process during alumina production. It contains metals that are critical for a sustainable development of modern society. Due to a shortage of global resources of many metals, efficient large-scale processing of RM has been receiving increasing attention from both researchers and industry. This study investigated the solubilization of metals from RM, together with RM dealkalization, via sulfur (S0) oxidation catalyzed by the moderately thermophilic bacterium Sulfobacillus thermosulfidooxidans. Optimization of the bioleaching process was conducted in shake flasks and 5-L bioreactors, with varying S0:RM mass ratios and aeration rates. The ICP analysis was used to monitor the concentrations of dissolved elements from RM, and solid residues were analyzed for surface morphology, phase composition, and Na distribution using the SEM, XRD, and STXM techniques, respectively. The results show that highest metal recoveries (89% of Al, 84% of Ce, and 91% of Y) were achieved with the S0:RM mass ratio of 2:1 and aeration rate of 1 L/min. Additionally, effective dealkalization of RM was achieved under the above conditions, based on the high rates (>95%) of Na, K, and Ca dissolution. This study proves the feasibility of using bacterially catalyzed S0 oxidation to simultaneously dealkalize RM and efficiently extract valuable metals from the amassing industrial waste.

The effect of mixotrophy on microalgal growth, lipid content, and expression levels of three pathway genes in Chlorella sorokiniana.

Nannochloropsis oculata CCMP 525, Dunaliella salina FACHB 435, and Chlorella sorokiniana CCTCC M209220 were compared in mixotrophic and photoautotrophic cultures in terms of growth rate, protein, and lipid content. Growth improved in glucose, and the biomass productivities of N. oculata, D. salina, and C. sorokiniana were found to be 1.4-, 2.2- and 4.2-fold that observed photoautotrophically. However, biomass and lipid production decreased at the highest glucose concentrations. Meanwhile, the content of protein and lipid were significantly augmented for mixotrophic conditions at least for some species. C. sorokiniana was found to be well suited for lipid production based on its high biomass production rate and lipid content reaching 51% during mixotrophy. Expression levels of accD (heteromeric acetyl-CoA carboxylase beta subunit), acc1 (homomeric acetyl-CoA carboxylase), rbcL (ribulose 1, 5-bisphosphate carboxylase/oxygenase large subunit) genes in C. sorokiniana were studied by real-time PCR. Increased expression levels of accD reflect the increased lipid content in stationary phase of mixotrophic growth, but expression of the acc1 gene remains low, suggesting that this gene may not be critical to lipid accumulation. Additionally, reduction of expression of the rbcL gene during mixotrophy indicated that utilization of glucose was found to reduce the role of this gene and photosynthesis.

Effects of copper exposure on expression of glutathione-related genes in Acidithiobacillus ferrooxidans.

The response of Acidithiobacillus ferrooxidans to variations in extracellular Cu exposure was investigated in terms of glutathione-related genes expression profiling based on reverse-transcription quantitative PCR analysis. The results show that the higher concentration of Cu would induce the expression of glutathione-related enzymes and cells elicited specific transcriptional responses when challenged with environmental Cu (0.08 mol l(-1)) conditions over a 60-min period. In comparison to the control, glutathione S-transferases (GST) and glutathione reductase (GR) were highly expressed when the cells were grown in the medium with copper, and the increase of glutathione and glutathione-related enzymes makes the cells acclimate to oxidative stress induced by Cu and protects the cells from toxicity caused by Cu exposure. It suggests that in order for Acidithiobacillus ferrooxidans to counteract the conditions of external Cu exposure, it modulated its expression level of GST, GR, glutathione hydrolase, and glutathione synthetase, which may protect organisms from oxidative damage. These parameters may be used to assess the biological impact of Cu in mining activities.