Activity Of Iron Oxide Research Articles

Comparative Study of Antioxidant Activity of Dextran-Coated Iron Oxide, Gold, and Silver Nanoparticles Against Age-Induced Oxidative Stress in Erythrocytes.

Erythrocytes undergo several changes during human aging and age-related diseases and, thus, have been studied as biomarkers of the aging process. The present study aimed to explore the antioxidant ability of metal and metal oxide nanoparticles (NPs) such as iron oxide (Fe3O4), gold (Au), and silver (Ag) to mitigate age-related oxidative stress in human erythrocytes. Metal and metal oxide NPs behave like antioxidative enzymes, directly influencing redox pathways and thus have better efficiency. Additionally, biopolymer coatings such as dextran enhance the biocompatibility of these NPs. Therefore, dextran-coated Fe3O4, Au, and Ag NPs were synthesized using wet chemical methods and were characterized. Their hemocompatibility and ability to protect erythrocytes from age-induced oxidative stress were investigated. The Fe3O4 and Au NPs were observed to protect erythrocytes from hydrogen peroxide and age-induced oxidative damage, including decreased antioxidant levels, reduced activity of antioxidative enzymes, and increased amounts of oxidative species. Pretreatment with NPs preserved the morphology and membrane integrity of the erythrocyte. However, Ag NPs induced oxidative stress in erythrocytes similar to hydrogen peroxide. Therefore, dextran-coated Fe3O4 and Au nanoparticles have the potential to be employed as antioxidant therapies against age-related oxidative stress.

Casein phosphopeptide interferes the interactions between ferritin and ion irons

Ferritin, a vital protein required to store iron in a cage-like structure, is critical for maintaining iron balance. Ferritin can be attacked by free radicals during iron reduction and release, thereby leading to oxidative damage. Whether other biomacromolecules such as casein phosphopeptides (CPP) could influence the ferritin's function in iron oxidation and release and affect the ferritin stability remains unclear. This study aims to investigate the effect of CPP on the ferritin‑iron ion interaction, thereby focusing on role of CPP on ferritin stability. Results showed that CPP weakened the iron oxidation activity of ferritin but promoted iron release. Moreover, CPP could effectively chelate iron, capture hydroxyl radicals, and reduce the degradation of ferritin. This study highlights the role of CPP in the ferritin‑iron relationship, and lays a foundation for understanding the interaction between ferritin, peptides, and metal ions.

A Physical Insight of Phase-Dependent Electron Transfer Kinetic Behaviors and Electrocatalytic Activity of an Iron Oxide-Based Sensing Nanoplatform Towards Chloramphenicol

Insight into the phase-dependent electron transfer kinetics and electrocatalytic activity of metal oxide nanostructures is important in the rational design of functional nanostructures for realizing high-performance electrochemical sensors. This study focuses on elucidating the effect of the crystalline phase on the electron transfer kinetics and electrocatalytic activity of iron(III) oxide. The α-FeOOH, γ-Fe2O3, and α-Fe2O3 nanorods were designed by using a simple chemical method and calcining process. The phase-dependent difference in the electron transfer kinetics and electrocatalytic activity toward the sensitive response of chloramphenicol (CAP) is observed by the transformation from α-FeOOH to γ-Fe2O3, and from α-FeOOH to α-Fe2O3 nanorods. We found that the oxygen vacancies formed in phase transformation from α-FeOOH to α-Fe2O3 is a key factor in promoting the electrochemical reduction of chloramphenicol. The α-Fe2O3 nanorods-based electrochemical sensors showed a linear response in the CAP concentration range from 0.1 to 75 μM with a limit of detection of 60 nM and an electrochemical sensitivity of 2.86 μA μM−1 cm−2. This work further provides valuable physical insight into the phase-dependent electron transfer kinetics and electrocatalytic activity of metal oxide nanostructures for the rational design of sensing interface.

Activity of Iron Oxide in Slag with Nepheline Syenite Added as a Flux

Activity of Iron Oxide in Slag with Nepheline Syenite Added as a Flux

Nanozymes: Definition, Activity, and Mechanisms.

"Nanozyme" is used to describe various catalysts from immobilized inorganic metal complexes, immobilized enzymes to inorganic nanoparticles. Here, the history of nanozymes is dvescribed in detail, and they can be largely separated into two types. Type 1 nanozymes refer to immobilized catalysts or enzymes on nanomaterials, whichweredominant in the first decade since 2004. Type 2 nanozymes, which rely on the surface catalytic properties of inorganic nanomaterials, are the dominating type in the past decade. The definition of nanozymes is evolving, and a definition based on the same substrates and products as enzymes are able to cover most currently claimed nanozymes, although they may have different mechanisms compared to their enzyme counterparts. A broader definition can inspire application-based research to replace enzymes with nanomaterials for analytical, environmental, and biomedical applications. Comparison with enzymes also requires a clear definition of a nanozyme unit. Four ways of defining a nanozyme unit are described, with iron oxide and horseradish peroxidase activity comparison as examples in each definition. Growing work is devoted to understanding thecatalytic mechanism of nanozymes, which provides a basis for further rational engineering of active sites. Finally, future perspective of the nanozyme field is discussed.

In vitro antibacterial and cytotoxic activity of zinc oxide, iron oxide and silver nanoparticles synthesised from Artemisia afra

The synthesis of nanoparticles using medicinal plants is a potential pathway for developing environmentally friendly drugs with minimal side effects. The aim of this study was to isolate heptadecyl-trans-p-coumarate from the medicinal plant, Artemisia afra, utilise it and its extract to synthesise silver nanoparticles (AgNPs), zinc oxide nanoparticles (ZnONPs) and iron oxide nanoparticles (Fe2O3NPs) that were evaluated for antibacterial and cytotoxic activity. AgNPs synthesised from the coumarate and extract were mostly spherical with an average size of 12 nm and 29 nm, respectively. ZnONPs were mostly rods, plates and spheres with average sizes of 31 nm (extract) and 22 nm (coumarate). Fe2O3NPs were hexagons and spheres with average sizes of 31 nm (extract) and 24 nm (coumarate). Nanoparticles improved the antibacterial activity of the extract and coumarate against Escherichia coli, Pseudomonas aeruginosa, Chromobacterium violaceum and Staphylococcus aureus. Shape of nanoparticles influenced activity; rod-shaped ZnONPs and platelet-like Fe2O3NPs synthesised using the extract exhibited better antibacterial activity. Spherical ZnONPs synthesised using the coumarate and spherical AgNPs showed greater cytotoxicity. The results suggest a synergistic effect between the metal nanoparticles and capping agents. Overall, this study confirms the use of Artemisia afra for the biosynthesis of silver, zinc oxide and iron oxide nanoparticles.

Characterization and genomic analysis of two novel psychrotolerant Acidithiobacillus ferrooxidans strains from polar and subpolar environments.

The bioleaching process is carried out by aerobic acidophilic iron-oxidizing bacteria that are mainly mesophilic or moderately thermophilic. However, many mining sites are located in areas where the mean temperature is lower than the optimal growth temperature of these microorganisms. In this work, we report the obtaining and characterization of two psychrotolerant bioleaching bacterial strains from low-temperature sites that included an abandoned mine site in Chilean Patagonia (PG05) and an acid rock drainage in Marian Cove, King George Island in Antarctic (MC2.2). The PG05 and MC2.2 strains showed significant iron-oxidation activity and grew optimally at 20°C. Genome sequence analyses showed chromosomes of 2.76 and 2.84 Mbp for PG05 and MC2.2, respectively, and an average nucleotide identity estimation indicated that both strains clustered with the acidophilic iron-oxidizing bacterium Acidithiobacillus ferrooxidans. The Patagonian PG05 strain had a high content of genes coding for tolerance to metals such as lead, zinc, and copper. Concordantly, electron microscopy revealed the intracellular presence of polyphosphate-like granules, likely involved in tolerance to metals and other stress conditions. The Antarctic MC2.2 strain showed a high dosage of genes for mercury resistance and low temperature adaptation. This report of cold-adapted cultures of the At. ferrooxidans species opens novel perspectives to satisfy the current challenges of the metal bioleaching industry.

Quality or Quantity? How Structural Parameters Affect Catalytic Activity of Iron Oxides for CO Oxidation

The replacement of noble metal catalysts by abundant iron as an active compound in CO oxidation is of ecologic and economic interest. However, improvement of their catalytic performance to the same level as state-of-the-art noble metal catalysts requires an in depth understanding of their working principle on an atomic level. As a contribution to this aim, a series of iron oxide catalysts with varying Fe loadings from 1 to 20 wt% immobilized on a γ-Al2O3 support is presented here, and a multidimensional structure–activity correlation is established. The CO oxidation activity is correlated to structural details obtained by various spectroscopic, diffraction, and microscopic methods, such as PXRD, PDF analysis, DRUVS, Mössbauer spectroscopy, STEM-EDX, and XAS. Low Fe loadings lead to less agglomerated but high percentual amounts of isolated, tetrahedrally coordinated iron oxide species, while the absolute amount of isolated species reaches its maximum at high Fe loadings. Consequently, the highest CO oxidation activity in terms of turnover frequencies can be correlated to small, finely dispersed iron oxide species with a large amount of tetrahedrally oxygen coordinated iron sites, while the overall amount of isolated iron oxide species correlates with a lower light-off temperature.

A Biodegradable High-Efficiency Magnetic Nanoliposome Promotes Tumor Microenvironment-Responsive Multimodal Tumor Therapy Along with Switchable T2 Magnetic Resonance Imaging.

We explored the catalytic activity and magnetic resonance imaging (MRI) capacity of Cu-doped ultrasmall iron oxides with different doping ratios. Then, we screened a highly efficient ultrasmall active catalyst (UAC). Subsequently, a biodegradable magnetic nanoliposome was developed for multimodal cancer theranostics through pH-sensitive liposome coating of these UACs. Upon entering the body, the magnetic nanoliposomes significantly prolonged the metabolic time of UACs and promoted their accumulation in tumors. Then, the strong photothermal (PT) effect of the magnetic nanoliposome quickly ablated the tumor, showing promising PT therapy. Upon entering tumor cells, the magnetic nanoliposome rapidly degraded into many UACs and released chemotherapeutic drugs, contributing to chemotherapy. In addition, UACs not only catalyzed Fenton-type reaction to produce excessive reactive oxygen species (ROS) but also inhibited the synthesis of endogenous GSH by inactivating glutamyl cysteine ligase, contributing to cancer ferroptosis. Furthermore, the assembly-dissociation process of UACs showed the function of magnetic relaxation switches, significantly enhancing tumor MRI signal change, achieving a more accurate diagnosis of the tumor. Therefore, this magnetic nanoliposome splits into many UACs upon drug release and regulates the tumor microenvironment to overproduce ROS for enhanced synergistic tumor theranostics, which provides a strategy for developing next-generation magnetic catalysts with biodegradability and multimodal antitumor theranostics.

Growth in ever-increasing acidity condition enhanced the adaptation and bioleaching ability of Leptospirillum ferriphilum.

Low pH eliminated the jarosite accumulation and improved the interfacial reaction rate during the bioleaching process. However, high acidity tends to make environments less hospitable, even for organisms that live in extreme places, so a great challenge existed for bioleaching at low pH conditions. This study demonstrated that the adaption and bioleaching ability of Leptospirillum ferriphilum could be improved after the long-term adaptive evolution of the community under acidity conditions. It was found that the acidity-adapted strain showed robust ferrous iron oxidation activity in wider pH, high concentration of ferrous iron, and lower temperature. Although the enhancement for heavy metal tolerance was limited, the resistance for MgSO4, Na2SO4, and organic matter was stimulative. More importantly, both pyrite and printed circuit board bioleaching revealed the higher bioleaching ability of the acid-resistant strain. These adaptation and bioleaching details provided an available approach for the improvement of bioleaching techniques.

The Change in the Structure and Functionality of Ferritin during the Production of Pea Seed Milk.

Understanding the effect of thermal treatment on the physical and chemical properties of protein and its mechanisms has important theoretical implications in food science. Pea seed ferritin (PSF) is an iron storage protein naturally occurring in pea seeds, which represents a promising iron supplement. However, how thermal processing affects the structure and function of PSF remains unknown. In this work, during the production of pea seed milk, we investigated the effect of thermal treatments at boiling temperature for two different times (5 and 10 min), respectively, on the structure and function of PSF. The results demonstrated that thermal treatment resulted in a pronounced change in the primary, secondary, and tertiary structure, iron content, and iron oxidation activity of PSF. However, the shell-like structure of PSF can be kept during the processing of pea seed milk. Interestingly, upon thermal treatment, both thermal-treated samples exhibit larger higher iron absorption rate by Caco-2 than untreated PSF at the same protein concentration. Such an investigation provides a better understanding of the relationship between the structure and function of food protein, as affected by thermal treatment.

Towards recycling remediated cyanidation tailings water to the mineral biooxidation process – Impact on microbial community and its performance

Biooxidation is a well-established pretreatment technology used in refractory gold mineral processing to enhance metal value recovery. The technology is microbially-mediated and is dependent on appropriate quality water for optimum function. The influence of remediated cyanidation tailings effluent and increasing thiocyanate (SCN−) concentration on a biooxidation microbial community was evaluated in small-scale batch tests. Changes in ferrous iron (Fe2+) oxidation activity, microbial growth and microbial community structure were evaluated. Two detoxified tailings wastewater samples, one sourced from an industrial operation and another from a laboratory system, were evaluated and used as the liquid matrix for medium preparation. These were compared with a standard laboratory medium described for the cultivation of acidophilic biooxidation organisms. Additionally, the effect of increasing SCN− concentration over the range of 0–5 mg/L across the different nutrient matrices. Similar microbial growth and Fe2+ oxidation activity with a nominal shift in community structure were observed in nutrient media containing remediated tailings wastewater relative to experiments conducted using defined medium prepared with deionised water (dH2O). However, a lag in the onset of Fe2+ oxidation activity was observed in systems cultured in media containing remediated effluent. This was attributed to the coupled presence of anions, NO3– and SCN−, in conjunction with additional constituents within the remediated effluent matrix. Exposure to SCN− concentrations up to 1 mg/L across all nutrient media demonstrated marginal differences in Fe2+ oxidation performance, although the observed lag in Fe2+ oxidation activity was sustained in remediated effluent tests. At a SCN– concentration of 1.4 mg/L Fe2+ oxidation activity within the defined medium system was inhibited, however systems cultivated in remediated tailings water exhibited sustained Fe2+ oxidation performance at 1.4 mg SCN− mg/L. Exposure to SCN− concentrations above 1.4 mg/L resulted in negligible Fe2+ oxidation activity, lower cell concentrations and a significant increase in growth lag time in detoxified tailings water media. Microbial community structure data illustrated that Leptospirillum ferriphilum was the dominant Fe2+ oxidising species within all systems; and its decline in abundance at elevated SCN− concentrations corresponded to poor Fe2+ utilisation. The abundance (and inferred growth rate) of sulfur-oxidising Acidithiobacillus caldus remained constant across the SCN− range explored. Abundance of Acidiplasma cupricumulans was found to increase at SCN− concentrations above 1 mg/L; however, it did not contribute toward Fe2+ oxidation. Results from this study indicated that inclusion of remediated tailings wastewater within the biooxidation circuit would be feasible causing negligible disruption to process performance; however, SCN− concentrations should not exceed 1 mg/L.

Comparative photocatalytic degradation of dyes in wastewater using solar enhanced iron oxide (Fe2O3) nanocatalysts prepared by chemical and microwave methods

This study involves comparing the different morphologies and photocatalytic activity of iron oxides (Fe2O3) nanoparticles synthesized by using the chemical heating method and microwave-assisted method. Characterization of the synthesized iron oxides nanoparticles was carried out using spectroscopic and microscopic techniques. The photocatalytic activity of the synthesized Fe2O3 nanoparticles on the degradation of two different hazardous dyes (Murexide and Eriochrome Black-T (EBT)) was investigated. The microwave synthesized Fe2O3-nanoparticles gave the highest degradation efficiency towards Murexide (98%) and EBT (96%) dyes at 25 mg loading and 40 mins exposure time, while chemically synthesized Fe2O3 nanoparticles gave the highest degradation efficiency (15.2%) at 5 mg loading and 30 mins sunlight exposure time in Murexide dye. The highest degradation efficiency of the chemically synthesized Fe2O3 nanoparticles in EBT (21.4%) was obtained with 15 mg catalyst loading after 40 min exposure time. The study, therefore, concluded that the microwave synthesized nanoparticles would be preferred to the chemical method for the treatment of industrial wastewater containing organic dyes such as EBT and Murexide dyes.

The antibacterial effect of iron oxide and graphene oxide nanoparticles and their nanocomposites against Escherichia coli and Staphylococcus aureus bacteria

Excessive use of antibiotics in the livestock and poultry industry has led to antibiotic resistance in livestock and humans. The use of metal Nano-oxides and nanocomposites has been considered as a new strategy to combat infectious diseases. In this study, the antibacterial activity of iron oxide and graphene oxide nanoparticles and their nanocomposites were investigated. aureus; S. For this purpose, antibacterial activity of iron oxide (Fe2o3; F), Graphene oxide (GO), 0.018g reduced graphene oxide-Fe2O3 Nanocomposite (FG1), 0.036g reduced graphene oxide-Fe2O3 Nanocomposite (FG2), 0.072g reduced graphene oxide-Fe2O3 Nanocomposite (FG3) against Gram-negative (Escherichia coli; E. coli) and Gram-positive (Staphylococcus aureus) bacteria was screened. The antibacterial activity of the five different nanoparticles was assessed by minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and the time-kill assay methods. The antibacterial results showed that except for FG1, for the rest of the nanoparticles MIC were 60 μL/mL for E. coli and 50 μL/mL for S. aureus. Moreover, the time-kill assay revealed that the growth of both bacteria was inhibited from the 2nd hour onwards for all nanoparticles. In general, the results of this study showed that iron oxide and graphene oxide nanocomposites increase their antibacterial effect.

Ferritin with Atypical Ferroxidase Centers Takes B-Channels as the Pathway for Fe2+ Uptake from Mycoplasma

Here, we present a 1.9 Å resolution crystal structure of Mycoplasma Penetrans ferritin, which reveals that its ferroxidase center is located on the inner surface of ferritin but not buried within the four-helix of each subunit. Such a ferroxidase center exhibits a lower iron oxidation activity as compared to the reported ferritin. More importantly, we found that Fe2+ enters into the center via the rarely reported B-channels rather than the normal 3- or 4-fold channels. All these findings may provide the structural bases to explore the new iron oxidation mechanism adopted by this special ferritin, which is beneficial for understanding the relationship between the structure and function of ferritin.

Evaluation of the Ecological Potential of Microorganisms for Purifying Water with High Iron Content

The ability of a number of microorganisms isolated from highly magnetic soil of the city Mednogorsk to oxidize Fe (II) under conditions of periodic cultivation in a liquid medium was studied. Among the studied microorganisms, two microbial isolates with maximum growth characteristics and iron-oxidizing activity were selected and identified: Bacillus megaterium 69.3 and B. megaterium 69.5. Individual levels of metal resistance of the isolates were determined: maximum tolerated concentration (MTC) for Fe (II) of the isolates B. megaterium 69.3 and B. megaterium 69.5 was 1200 mg L−1, minimum inhibitory concentration (MIC) was 1800 mg L−1. Both microbial isolates actively oxidized Fe (II) by reducing its high concentration in the medium (1.19 g L−1) by 33 and 39% during 14 days of culturing. Total increase in the biomass of B. megaterium 69.3 and B. megaterium 69.5 after 14 days of culturing was 15.3 and 14.7 g L−1; the active parts of the biomass increased 8.7- and 6.9-fold compared to the inoculum dose, respectively. These microbial isolates could be used in future in the biotechnological process of water purification with increased/high levels of Fe (II).

From Laboratory towards Industrial Operation: Biomarkers for Acidophilic Metabolic Activity in Bioleaching Systems.

In the actual mining scenario, copper bioleaching, mainly raw mined material known as run-of-mine (ROM) copper bioleaching, is the best alternative for the treatment of marginal resources that are not currently considered part of the profitable reserves because of the cost associated with leading technologies in copper extraction. It is foreseen that bioleaching will play a complementary role in either concentration—as it does in Minera Escondida Ltd. (MEL)—or chloride main leaching plants. In that way, it will be possible to maximize mines with installed solvent-extraction and electrowinning capacities that have not been operative since the depletion of their oxide ores. One of the main obstacles for widening bioleaching technology applications is the lack of knowledge about the key events and the attributes of the technology’s critical events at the industrial level and mainly in ROM copper bioleaching industrial operations. It is relevant to assess the bed environment where the bacteria–mineral interaction occurs to learn about the limiting factors determining the leaching rate. Thus, due to inability to accurately determine in-situ key variables, their indirect assessment was evaluated by quantifying microbial metabolic-associated responses. Several candidate marker genes were selected to represent the predominant components of the microbial community inhabiting the industrial heap and the metabolisms involved in microbial responses to changes in the heap environment that affect the process performance. The microbial community’s predominant components were Acidithiobacillus ferrooxidans, At. thiooxidans, Leptospirillum ferriphilum, and Sulfobacillus sp. Oxygen reduction, CO2 and N2 fixation/uptake, iron and sulfur oxidation, and response to osmotic stress were the metabolisms selected regarding research results previously reported in the system. After that, qPCR primers for each candidate gene were designed and validated. The expression profile of the selected genes vs. environmental key variables in pure cultures, column-leaching tests, and the industrial bioleaching heap was defined. We presented the results obtained from the industrial validation of the marker genes selected for assessing CO2 and N2 availability, osmotic stress response, as well as ferrous iron and sulfur oxidation activity in the bioleaching heap process of MEL. We demonstrated that molecular markers are useful for assessing limiting factors like nutrients and air supply, and the impact of the quality of recycled solutions. We also learned about the attributes of variables like CO2, ammonium, and sulfate levels that affect the industrial ROM-scale operation.

Utilization of induction furnace steel slag based iron oxide nanocomposites for antibacterial studies

Metals and metal oxide-based nanocomposites play a significant role over the control of microbes. In this study, antibacterial activity of iron oxide (Fe2O3) nanocomposites based on induction furnace (IF) steel slag has been carried out. IF steel slag is an industrial by-product generated from secondary steel manufacturing process and has various metal oxides which includes Al2O3 (7.89%), MnO (5.06), CaO (1.49%) and specifically Fe2O3 (14.30%) in higher content along with metalloid SiO2 (66.42). Antibacterial activity of iron oxide nanocomposites has been revealed on bacterial species such as Micrococcus luteus, Bacillus subtilis and Staphylococcus aureus. Micrococcus luteus has undergone maximum zone of inhibition (ZOI) of 12 mm for 10 mg/mL concentration of steel slag iron oxide nanocomposite. Growth inhibitory kinetics of bacterial species has been studied using ELISA microplate reader at 660 nm by varying the concentration of steel slag iron oxide nanocomposites. The results illustrate that IF steel slag is a potential material and can be utilized in building materials to increase the resistance against biodeterioration.Graphic abstract

Ice nucleation activity of iron oxides via immersion freezing and an examination of the high ice nucleation activity of FeO.

Heterogeneous ice nucleation is a common process in the atmosphere, but relatively little is known about the role of different surface characteristics on the promotion of ice nucleation. We have used a series of iron oxides as a model system to study the role of lattice mismatch and defects induced by milling on ice nucleation activity. The iron oxides include wüstite (FeO), hematite (Fe2O3), magnetite (Fe3O4), and goethite (FeOOH). The iron oxides were characterized by X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) surface area measurements. The immersion freezing experiments were performed using an environmental chamber. Wüstite (FeO) had the highest ice nucleation activity, which we attribute to its low lattice mismatch with hexagonal ice and the exposure of Fe-OH after milling. A comparison study of MnO and wüstite (FeO) with milled and sieved samples for each suggests that physical defects alone result in only a slight increase in ice nucleation activity. Despite differences in the molecular formula and surface groups, hematite (Fe2O3), magnetite (Fe3O4), and goethite (FeOOH) had similar ice nucleation activities, which may be attributed to their high lattice mismatch to hexagonal ice. This study provides further insight into the characteristics of a good heterogeneous ice nucleus and, more generally, helps to elucidate the interactions between aerosol particles and ice particles in clouds.

Effect of Sodium Chloride on Pyrite Bioleaching and Initial Attachment by Sulfobacillus thermosulfidooxidans.

Biomining applies microorganisms to extract valuable metals from usually sulfidic ores. However, acidophilic iron (Fe)-oxidizing bacteria tend to be sensitive to chloride ions which may be present in biomining operations. This study investigates the bioleaching of pyrite (FeS2), as well as the attachment to FeS2 by Sulfobacillus thermosulfidooxidans DSM 9293T in the presence of elevated sodium chloride (NaCl) concentrations. The bacteria were still able to oxidize iron in the presence of up to 0.6M NaCl (35 g/L), and the addition of NaCl in concentrations up to 0.2M (~12 g/L) did not inhibit iron oxidation and growth of S. thermosulfidooxidans in leaching cultures within the first 7 days. However, after approximately 7 days of incubation, ferrous iron (Fe2+) concentrations were gradually increased in leaching assays with NaCl, indicating that iron oxidation activity over time was reduced in those assays. Although the inhibition by 0.1M NaCl (~6 g/L) of bacterial growth and iron oxidation activity was not evident at the beginning of the experiment, over extended leaching duration NaCl was likely to have an inhibitory effect. Thus, after 36 days of the experiment, bioleaching of FeS2 with 0.1M NaCl was reduced significantly in comparison to control assays without NaCl. Pyrite dissolution decreased with the increase of NaCl. Nevertheless, pyrite bioleaching by S. thermosulfidooxidans was still possible at NaCl concentrations as high as 0.4M (~23 g/L NaCl). Besides, cell attachment in the presence of different concentrations of NaCl was investigated. Cells of S. thermosulfidooxidans attached heterogeneously on pyrite surfaces regardless of NaCl concentration. Noticeably, bacteria were able to adhere to pyrite surfaces in the presence of NaCl as high as 0.4M. Although NaCl addition inhibited iron oxidation activity and bioleaching of FeS2, the presence of 0.2M seemed to enhance bacterial attachment of S. thermosulfidooxidans on pyrite surfaces in comparison to attachment without NaCl.