Oxidation Of Ferrous Iron Research Articles

Investigating the rus and petI operon expression patterns in exposed Acidithiobacillus ferrooxidans sp. FJ2 to different doses of gamma irradiation

The bioleaching process is developing as an economic and successful biotechnology method in the metallurgy industry. Acidithiobacillus ferrooxidans is one of the most important bacteria involved in uranium bioleaching which converts insoluble U4+ to soluble U6+ by oxidation of Fe2+ to Fe3+ using several periplasmic proteins encoded by the genes in rus and petI operons in its electron transport pathway. Accordingly, the purpose of this study was to consider the expression of these genes through exposed A. ferrooxidans sp. FJ2 to γ-ray in 17 different doses targeting uranium extraction yield.Acidithiobacillus ferrooxidans sp. FJ2 was irradiated by gamma rays at 25, 50, 75, 100, 150, 300, 450, 600, 750 Gy and 1, 2, 5, 10, 15, 20, 25 and 30 kGy doses. Moreover, the Eh value of 9k culture media was measured as special screening criteria to select the four treatments. The selected bacteria were cultured in 9k media, containing 50% uranium ore powder in the bioleaching process. Then, the value of pH & Eh of culture media, Fe2+ and uranium concentrations in 4, 8 and 13 day's period of incubation were measured. In followings, the expression levels of cyc1, cyc2, rus, coxB, petA, petB, petC and cycA genes at the end of each period were investigated by real-time PCR.Overall, all samples demonstrated a decrease in pH value and Fe2+ concentration and an increase in Eh value and U concentration in time intervals. The gamma irradiation in given doses raised the expression levels of all genes encoded in rus and petI operons, except petB gene during the bioleaching process, although, it had no effect either on the pH, Eh values or on Fe2+ and uranium concentrations.This result implies that during the oxidation of ferrous iron and formation of Jarosite sediment, the decreasing trend of pH and the increasing trend of Eh occurred in all samples. However, the differences in expression of the genes of rus and petI operons in the samples did not have an effect on uranium extraction.

Targeting mixtures of jarosite and clay minerals for Mars exploration

AbstractTerrestrial thermal environments can serve as analogs for subsurface environments in the search for life because they regularly host microbial communities, which may leave behind biosignatures. This study focused on an acid-sulfate hydrothermal site as an analog for a potentially habitable environment on Mars. A weathered boulder in the thermal area was dissected, revealing an interior marked with disconnected horizons of differently colored materials, very low pH, and increasing temperature. The mineralogy comprised weathering products from andesite (kaolinite, quartz, clinoptilolite) along with sulfate salts (alunite, jarosite, tschermigite, and copiapite) formed by oxidation of sulfide and ferrous iron. Characterization of organic matter in this boulder and several soil samples yielded interesting but surprising results. Both mass spectrometry and Raman spectroscopy identified organic compounds in portions of the soils and the boulder. Jarosite-associated samples showed more numerous and diverse organic signatures than did Al-bearing silicate samples, despite the lower total organic carbon content of the jarosite-associated soils (0.69 ± 0.07 wt% Corg) compared to the Al-bearing samples (1.28 ± 0.13 wt% Corg). Results from our geochemical, mineralogical, and spectroscopic study of hydrothermal alteration products and salts inform the heterogeneous distribution of inorganic and organic materials that could delineate habitats and demonstrate the limits on organic matter detectability using different analytical techniques. Furthermore, we relate our measurements and results directly to current and upcoming martian missions, and we provide recommendations for detection and characterization of minerals and organics as biosignatures on Mars using instruments on future missions.

Orbital forcing of ice sheets during snowball Earth

The snowball Earth hypothesis—that a runaway ice-albedo feedback can cause global glaciation—seeks to explain low-latitude glacial deposits, as well as geological anomalies including the re-emergence of banded iron formation and “cap” carbonates. One of the most significant challenges to snowball Earth has been sedimentological cyclicity that has been taken to imply more climate dynamics than expected when the ocean is completely covered in ice. However, recent climate models suggest that as atmospheric CO2 accumulates, the snowball climate system becomes sensitive to orbital forcing. Here we show the presence of nearly all Milankovitch (orbital) cycles preserved in stratified banded iron formation deposited during the Sturtian snowball Earth. These results provide evidence for orbitally forced cyclicity of global ice sheets that resulted in periodic oxidation of ferrous iron. Orbital glacial advance and retreat cycles provide a simple mechanism to reconcile both the sedimentary dynamics and the enigmatic survival of multicellular life during snowball Earth.

Characterization of the substrate binding site of an iron detoxifying membrane transporter from Plasmodium falciparum

BackgroundPlasmodium species are entirely dependent upon their host as a source of essential iron. Although it is an indispensable micronutrient, oxidation of excess ferrous iron to the ferric state in the cell cytoplasm can produce reactive oxygen species that are cytotoxic. The malaria parasite must therefore carefully regulate the processes involved in iron acquisition and storage. A 273 amino acid membrane transporter that is a member of the vacuolar iron transporter (VIT) family and an orthologue of the yeast Ca2+-sensitive cross complementer (CCC1) protein plays a major role in cytosolic iron detoxification of Plasmodium species and functions in transport of ferrous iron ions into the endoplasmic reticulum for storage. While this transporter, termed PfVIT, is not critical for viability of the parasite evidence from studies of mice infected with VIT-deficient Plasmodium suggests it could still provide an efficient target for chemoprophylactic treatment of malaria. Individual amino acid residues that constitute the Fe2+ binding site of the protein were identified to better understand the structural basis of substrate recognition and binding by PfVIT.MethodsUsing the crystal structure of a recently published plant VIT as a template, a high-quality homology model of PfVIT was constructed to identify the amino acid composition of the transporter’s substrate binding site and to act as a guide for subsequent mutagenesis studies. To test the effect of mutation of the substrate binding-site residues on PfVIT function a yeast complementation assay assessed the ability of overexpressed, recombinant wild type and mutant PfVIT to rescue an iron-sensitive deletion strain (ccc1∆) of Saccharomyces cerevisiae yeast from the toxic effects of a high concentration of extracellular iron.ResultsThe combined in silico and mutagenesis approach identified a methionine residue located within the cytoplasmic metal binding domain of the transporter as essential for PfVIT function and provided insight into the structural basis for the Fe2+-selectivity of the protein.ConclusionThe structural model of the metal binding site of PfVIT opens the door for rational design of therapeutics to interfere with iron homeostasis within the malaria parasite.

Comparative insights into genome signatures of ferric iron oxide- and anode-stimulated Desulfuromonas spp. strains

BackgroundHalotolerant Fe (III) oxide reducers affiliated in the family Desulfuromonadaceae are ubiquitous and drive the carbon, nitrogen, sulfur and metal cycles in marine subsurface sediment. Due to their possible application in bioremediation and bioelectrochemical engineering, some of phylogenetically close Desulfuromonas spp. strains have been isolated through enrichment with crystalline Fe (III) oxide and anode. The strains isolated using electron acceptors with distinct redox potentials may have different abilities, for instance, of extracellular electron transport, surface recognition and colonization. The objective of this study was to identify the different genomic signatures between the crystalline Fe (III) oxide-stimulated strain AOP6 and the anode-stimulated strains WTL and DDH964 by comparative genome analysis.ResultsThe AOP6 genome possessed the flagellar biosynthesis gene cluster, as well as diverse and abundant genes involved in chemotaxis sensory systems and c-type cytochromes capable of reduction of electron acceptors with low redox potentials. The WTL and DDH964 genomes lacked the flagellar biosynthesis cluster and exhibited a massive expansion of transposable gene elements that might mediate genome rearrangement, while they were deficient in some of the chemotaxis and cytochrome genes and included the genes for oxygen resistance.ConclusionsOur results revealed the genomic signatures distinctive for the ferric iron oxide- and anode-stimulated Desulfuromonas spp. strains. These findings highlighted the different metabolic abilities, such as extracellular electron transfer and environmental stress resistance, of these phylogenetically close bacterial strains, casting light on genome evolution of the subsurface Fe (III) oxide reducers.

Congenital Methemoglobinemia Under Diagnosed Condition with Variiable Therapeurtic Options

Methemoglobinemia is a rare overlooked differential diagnosis in patients with cyanosis and dyspnea unrelated to cardiopulmonary causes.Methemoglobin results from oxidation of ferrous iron to ferric iron within the heme moiety of hemoglobin . In healthy individuals, less than 1% of hemoglobin is present in the oxidized form (methemoglobin), which has limited ability to carry oxygen, however with increased oxygen affinity at the remaining binding sites .This results in decrease of oxygen delivery to tissue leading to hypoxaemia and lactic acidosis.Methemoglobin reductase enzyme deficiency is either type I or type II; type I: Cytochrome b5 reductase deficiency, demonstrable only in the erythrocytes, presents as uncomplicated, benign methemoglobinemia, and associated with a normal life expectancy with only fatigue and dyspnea being the most commonly reported symptoms.Hereditary type II methemoglobinemia, is global (affects both red and white blood cells) and is associated with severe neurologic dysfunction and reduced life expectancy . The enzyme's activity is less than 20% of normal.Type II congenital methemoglobinemia constitutes approximately 10% of all cases of congenital methemoglobinemia and usually causes death within the first few years of lifeThere is a significant delay in the onset of symptoms in a patient with type I hereditary methemoglobinemia, as most studies indicate that patients are asymptomatic in infancy and childhood.we report a 29 year old Indian non-smoker male, his story started 6 months prior to presentation when he had generalized fatigue and discoloration of hands. He presented with persistent polycythaemia with elevated hemoglobin level. The patient was misdiagnosed in another center as polycythaemia and treated with Imatinib. The diagnosis of PV was revisited and ruled out in view of negative JAK2, normal erythropoietin level and absence of features of panmyelosis.Clinical cyanosis and low oxygen saturation in the presence of normal arterial oxygen tension was highly suggestive of methemoglobinemia.Arterial blood gas (ABG) revealed a methemoglobin level of 38% (normal: 0-1.5%). Cytochrome B5 reductase (Methemoglobin reductase B) wasdeficient at level of <2.6 U/g Hb) (normal: 6.6-13.3), consistent with methemoglobin reductase (cytochrome b5) deficiency and hence the diagnosis of congenital methemoglobinemia was established.The role of Imatinib in provoking methemoglobinemia is questionable and association between Imatinib and methemoglobinemia never described before. There was no history of other drugs offended in aggravating the patients' symptoms and cyanosis.The patient started on Vitamin C 500 mg for which he responded well with less cyanosis and significant reduction of methemoglobin level.Upon extensive review of English literature for cases of congenital Methaemoglobinaemia due to deficiency of cytochrome b5 reductase, we found 23 cases diagnosed as type I (including the case reported here).17 cases (~74%) of type I and 6 cases (27%) of type II. There is male predominance (73%) versus 26% in females. Almost half of reported cases (12 cases; 52%) are indian, 2 Japanese, 3 English, 2 Arabic, one Spanish and one Italian.For type I, the median calculated age is 31 years with cyanosis and shortness of breath being the most common sign and symptom.For type II: Six cases were reported, all in pediatric age group with median calculated age at presentation is 6 years with neurologic manifestations and mental retardation are the most common type II associated symptoms.Congenital methemogobinemia is a rare underreported hemoglobin disease. Due to lack of systematic epidemiological studies it is usually under investigated and frequently clinically missed especially when presenting in adulthood. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Generation of reactive oxygen species from oxygen microbubbles in phosphoric acid solution and its application of ferrous iron oxidation

BackgroundMicrobubbles have been widely used in advanced oxidation processes due to the generation of reactive oxygen species (ROS). In this study, the oxidation of ferrous ions in phosphoric acid solutions has been examined, focusing on the advanced oxidation activity of oxygen microbubbles. MethodsUltraviolet spectroscopy was used to determine the species and content of ROS. Electron spin-resonance spectroscopy and radical quenching experiments have confirmed the path of ROS generation. Significant findingsIt is concluded that the main ROS in the phosphoric acid solution was H2O2, and the generation of H2O2 was due to sequential single electron reduction of oxygen molecules. The amount of H2O2 generated was determined to be dependent on the temperature and phosphoric acid concentration, and under the optimal conditions (100 ºC and 7 mol/L H3PO4), 4.23 mmol/L H2O2 was produced from microbubbles. The kinetics analysis with respect to the oxidation of ferrous ions suggested significant reduction of reaction activation energy from greater than 56.1kJ/mol to 43.84 kJ/mol due to the oxidation via ROS, demonstrating that microbubble intensification is a facile and effective advanced oxidation method.

Dispersion of sulfur creates a valuable new growth medium formulation that enables earlier sulfur oxidation in relation to iron oxidation in Acidithiobacillus ferrooxidans cultures.

Acidithiobacillus ferrooxidans is an acidophilic chemolithoautotroph that is commonly reported to exhibit diauxic population growth behavior where ferrous iron is oxidized before elemental sulfur when both are available, despite the higher energy content of sulfur. We have discovered sulfur dispersion formulations that enables sulfur oxidation before ferrous iron oxidation. The oxidation of dispersed sulfur can lower the culture pH within days below the range where aerobic ferrous iron oxidation can occur. Thus, ferric iron reduction can be observed quickly which had previously been reported over extended incubation periods with untreated sulfur. Therefore, we demonstrate that this substrate utilization pattern is strongly dependent on the cell loading in relation to sulfur concentration, sulfur surface hydrophobicity, and the pH of the culture. Our dispersed sulfur formulation, lig-sulfur, can be used to support the rapid antibiotic selection of plasmid-transformed cells, which is not possible in liquid cultures where ferrous iron is the main source of energy for these acidophiles. Furthermore, we find that media containing lig-sulfur supports higher production of green fluorescent protein compared to media containing ferrous iron. The use of dispersed sulfur is a valuable new tool for the development of engineered A. ferrooxidans strains and it provides a new method to control iron and sulfur oxidation behaviors.

Modeling of mechanical characteristics of composite materials applied for protection of information and control complexes of aircraft

In modern conditions of electronic warfare, effective protection of information and control complexes of aircraft (AC) from the destructive effects of external interference is impossible without the use of innovative solutions in the field of creating new composite materials (CM) with radio-absorbing properties. This scientific area is inextricably linked with the issues of predicting the properties of these materials. A wide variety of design solutions to protect aircraft “electronics”, as well as a wide range of electromagnetic and mechanical effects, require the creation of functional materials for specific operating conditions. Thus, the developers of functional materials must have an effective tool to predict the properties of the CM being created. Solutions can be based on mathematical models that allow predicting the properties of CM and subsequently optimizing their composition. The article discusses the identification and verification of mathematical models of the mechanical characteristics of CMs based on BASF polyurethane with the addition of both untreated and processed ferric iron oxide as a filler, with subsequent optimization of the characteristics and determination of the corresponding CM composition with radio-absorbing properties. Experimental studies have been carried out, which confirm the adequacy of the developed mathematical models.

Coupling oxidation of acid volatile sulfide, ferrous iron, and ammonia nitrogen from black-odorous sediment via autotrophic denitrification-anammox by nitrate addition

The coupling removal of acid volatile sulfide (AVS), ferrous iron, and ammonia nitrogen has been applied for black-odorous sediment remediation. In this study, calcium nitrate with different N/(S + Fe) ratios (0.45, 0.90, 1.20 and 1.80) was added into black-odorous sediment in four systems named R1, R2, R3, and R4. Results showed that the removal rate of AVS was 76.40% in the R1, which was lower compared with rates in R2–R4 around 96.70%. The ferrous oxidation rate was approximately 87.00% in R2–R4, which was considerably higher than that in the R1 (24.62%). And the ammonia was reduced by 81.02%, 88.00%, 100%, and 57.18% in R1, R2, R3 and R4, respectively. During the reaction, nitrite accumulation was observed, indicating partial denitrification. Moreover, microbes related to autotrophic denitrification (e.g., genus Thiobacillus, Dok59, GOUTA19, Gallionella, with the highest abundance of 15.40%, 13.21%, 8.79%, 9.44%, respectively) were detected in all systems. Furthermore, the anammox bacteria Candidatus_Brocadia with the highest abundance of 3.44% and 4.00% in R2 and R3, respectively was also found. These findings confirmed that AVS, ferrous iron, and ammonia nitrogen could be simultaneously removed via autotrophic denitrification coupled with anammox in black-odorous sediment by nitrate addition.

Selection of optimal parameters of technological modes for the synthesis of polymer composite materials based on verified mathematical models

In the modern realities of creating structural elements for various purposes, polymer composite materials are widely used. These materials are used in almost all industries, from aerospace, shipbuilding, automotive, and ending with consumer goods. The article shows the need to develop mathematical models that reflect the relationship between mechanical properties and parameters of technological modes for the synthesis of polymer composite materials, to select the optimal parameters of the technological mode of their synthesis. The article discusses the optimization of a group of mechanical properties described by mathematical models built on the basis of a full factorial experiment, in order to obtain the optimal values of the parameters of the technological modes of synthesis of a polymer composite material based on heat-resistant low-molecular-weight synthetic rubber with the addition of ferric iron oxide as a filler. The research method is optimization by the method of successive concessions. Computer experiments have been carried out to optimize the parameters of technological modes for the synthesis of materials. The performed calculations were checked with experimental data, the adequacy of the obtained models was checked.

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.

Enhanced performance of microbial fuel cells with enriched ferrous iron oxidation microflora at room temperatures

Adding ferric ions (Fe3+) in catholyte can enhance performance of microbial fuel cells (MFCs). This work adopted biocathode with enriched Fe2+ oxidizing microflora to perform in situ Fe2+ oxidization so the MFC could operate with prolonged period with increased cell open circuit voltage (1037 mV) and maximum power density (71.8 Wm−3 at 154 Am−3) but with minimal needs for iron replenishment. The Fe2+-oxidizing microflora was very effective so the Fe3+/Fe2+ could reach high ratio, which was composed of Acidithiobacillus (73.8%), Acidiphilium (12.1%), Mycobacterium (6.92%), Sulfobacillus (2.66%), Ochrobactrum (1.30%), Alicyclobacillus (0.82%), and other minor species. The membrane transport and cell replication were shown to be their most important metabolic activities. The formation of jarosite and hydronium jarosite by Fe3+ and sulfate led to loss of iron ions, which should be minimized in operation.

The Effect of Metal Ions on the Growth and Ferrous IronOxidation by Leptospirillum ferriphilum CC Isolated from Armenia Mine Sites

The aim of this study is to investigate the potential of newly isolated strain Leptospirillum (L.) ferriphilum CC for bioleaching of pyrite and chalcopyrite in pure or mixed culture with other iron- and/or sulfur-oxidizing bacteria. In this paper, kinetics of ferrous iron (Fe2+) oxidation by newly isolated strain Leptospirillum (L.) ferriphilum CC was studied. The effect of initial Fe2+ in the concentration range of 50–400 mM on bacterial growth and iron oxidation was studied. It was shown that microbial Fe2+ oxidation was competitively inhibited by Fe3+. The influence of copper, zinc, nickel and cobalt ions on the oxidation of Fe2+ by L. ferriphilum CC was also studied. Minimal inhibitory concentrations (MIC) for each metal ion were determined. The toxicity of the ions was found to be as follows: Co &gt; Zn &gt; Ni &gt; Cu. The comparison of iron oxidation kinetic parameters of L. ferriphilum CC with other strains of L. ferriphilum indicates the high potential of strain L. ferriphilum CC for biogenic regeneration of concentrated ferric iron (Fe3+) in bioleaching processes of ores and ore concentrates. Bioleaching tests indicated that the newly isolated L. ferriphilum CC can be a prospective strain for the bioleaching of sulfide minerals in pure culture or in association with other iron- and/or sulfur-oxidizing bacteria.

RNA transcript response by an Acidithiobacillus spp. mixed culture reveals adaptations to growth on arsenopyrite.

Biooxidation of gold-bearing refractory mineral ores such as arsenopyrite (FeAsS) in stirred tanks produces solutions containing highly toxic arsenic concentrations. In this study, ferrous iron and inorganic sulfur-oxidizing Acidithiobacillus strain IBUN Ppt12 most similar to Acidithiobacillus ferrianus and inorganic sulfur compound oxidizing Acidithiobacillus sp. IBUNS3 were grown in co-culture during biooxidation of refractory FeAsS. Total RNA was extracted and sequenced from the planktonic cells to reveal genes with different transcript counts involved in the response to FeAsS containing medium. The co-culture's response to arsenic release during biooxidation included the ars operon genes that were independently regulated according to the arsenopyrite concentration. Additionally, increased mRNA transcript counts were identified for transmembrane ion transport proteins, stress response mechanisms, accumulation of inorganic polyphosphates, urea catabolic processes, and tryptophan biosynthesis. Acidithiobacillus spp. RNA transcripts also included those encoding the Rus and PetI proteins involved in ferrous iron oxidation and gene clusters annotated as encoding inorganic sulfur compound metabolism enzymes. Finally, mRNA counts of genes related to DNA methylation, management of oxidative stress, chemotaxis, and motility during biooxidation were decreased compared to cells growing without mineral. The results provide insights into the adaptation of Acidithiobacillus spp. to growth during biooxidation of arsenic-bearing sulfides.

Enhancement of the nitrogen-fixing activity of paddy soils owing to iron application

ABSTRACT Anaeromyxobacter and Geobacter, iron-reducing bacteria belonging to Deltaproteobacteria, are newly discovered nitrogen-fixing bacteria predominant in paddy soils. We hypothesized that adding ferric iron oxide as an electron acceptor for respiration of the iron-reducing bacteria could enhance the nitrogen-fixing activity of Anaeromyxobacter and Geobacter in paddy soils. In the soil microcosm study, soil nitrogen-fixing activity significantly increased after adding ferrihydrite or Fe2O3, ferric iron oxides, to the soil. In these soils, gene transcripts of nifD from Anaeromyxobacter and Geobacter were detected, whereas those from other general diazotrophs were not detected. Anaeromyxobacter and Geobacter might be involved in the enhanced soil nitrogen-fixing activity. The application of iron powder to paddy field soils also enhanced the soil nitrogen-fixing activity. This study is the first to demonstrate that addition of iron compounds to paddy soil enhanced the soil nitrogen-fixing activity. The results of this study may lead to the development of novel paddy soil management strategies to increase soil nitrogen fertility and ensure rice yields with a reduced nitrogen fertilizer input and a lower environmental nitrogen burden.

Identification and characterization of a metal-resistant Acidithiobacillus ferrooxidans as important potential application for bioleaching

Bioleaching is a common and eco-friendly method for the metals mobilization from mines, contaminated soils and wastes and it can be used in metal extraction and bioremediation. Due to the fact that these processes are considered as metabolism-dependent processes, isolation and identifying of the strains with high resistance features in responsible bacteria are one of the most important steps to have. In present study, an Iranian new isolate of iron-oxidizing bacteria was characterized. The phylogenetic analysis and 16S rRNA gene sequence of strain ZT-94 indicated that this strain is related to Acidithiobacillus ferrooxidans. It is investigated that the ferrous iron oxidation was increased dramatically in the early hours of bacterial growth and the ferrous iron (Fe2+) was completely oxidized at 30 h. According to the results, strain ZT-94 had the high tolerance capability to U, Ba, Al and Se. Iron oxidation by strain ZT-94 was inhibited by the addition of 312.5 mg/L Se and 70 mg/L Te but concentrations above 5000 mg/L of Ba and 2000 mg/L Al had no inhibitory effect on bacterial growth. In addition, strain ZT-94 was able to grow in the pH range of 1–4, temperatures at 25–35 °C. Results showed no inhibitory effects on bacterial growth rate in presence of 0.1 w/v organic compounds like fructose and glucose but a delayed growth was detected in presence of yeast extract in comparison with the others. The results showed that strain ZT-94 had high environmental adaptability and can be introduced as a suitable and valuable candidate for research in the bioleaching and bioremediation processes.

Hydrothermal formation of iron-oxyhydroxide chimney mounds in a shallow semi-enclosed bay at Satsuma Iwo-Jima Island, Kagoshima, Japan

Abstract Hydrothermal iron-oxyhydroxide chimney mounds (iron mounds) have been discovered in a fishing port in Nagahama Bay, located on the southwest coast of Satsuma Iwo-Jima Island, south of Kyushu Island, Japan. In the fishing port, uncovered ∼1.0-m-high iron mounds in shallow waters formed under relatively calm conditions. Typically, the fishing port has orange-colored turbid waters that mix with outer ocean waters during high tide. Colloidal iron-oxyhydroxides form due to the oxidation of ferrous iron in hydrothermal waters (pH = 5.5; temperature = 55 °C) as they mix with seawater. The mounds are made of two types of material: hard, dark brown–orange, high-density material; and soft, brownish orange–yellow, low-density material. Computed tomography scans of the harder iron mound material revealed a cabbage-like structure consisting of micropipe structures with diameters of 2–5 mm. These micropipes have relatively hard walls made of iron oxyhydroxides (FeOH) and are identified as discharge pipes. Nucleic acid staining genetic sequencing and scanning electron microscope observations suggest that the mounds formed mainly from bacterial stalks with high concentrations of FeOH colloidal matter. In the harder parts of the mounds, these “fat stalks,” which contain oxyhydroxide colloidal aggregates, are entwined and concentrated. The softer material contains twisted stalk-like structures, which are coated with FeOH colloidal particles. Deoxyribonucleic acid (DNA) examination of the iron mounds revealed the presence of iron-oxidizing bacteria, especially at the mound surface. We estimate that the iron mounds accumulated at a rate of ∼1700 tons/1000 m2/yr. This is an order of magnitude higher than the rate of FeOH sedimentation via chemical precipitation of FeOH colloids within the fishing port. This suggests that biogenic activity, resulting in the production of entwined FeOH stalks, leads to the rapid accumulation of FeOH beds and that biogenic activity within the water mass rich in FeOH colloids is an efficient means of generating thick iron-rich sedimentary sequences. As such, we propose that some ancient iron formations may have also formed through the biogenic production of FeOH stalks rather than solely through chemical sedimentation in a water mass rich in FeOH colloids. It appears that these rapidly forming biogenic FeOH iron mounds, distributed over a wide area of ocean floor, are also relatively protected from erosion and diagenetic alteration (reduction). Previous studies have reported that ancient iron formations were commonly deposited in deeper environments via direct iron oxidation from the water column in a ferruginous ocean. However, there are several hydrothermal vent inflows preserved with FeOH that would have formed appropriate redox boundary conditions in an otherwise anoxic ocean. Under these conditions, iron mound mat-type sedimentary deposits might have formed and been well preserved and affected by early diagenesis where higher heat flow occurred in the Archean ocean. The FeOH mounds in Nagahama Bay provide an example of the iron formation sedimentary environment and important information for estimating the past depositional state of iron formations.

The newest information for iron metabolism: ferric carboxymaltose, a recently available treatment option for iron-deficiency anemia

Iron-deficiency anemia (IDA) is the most common form of anemia. It is treated through iron replacement therapy, with oral iron administration as the recommended first-line treatment. However, intravenous (IV) iron formulation is at timed used owing to adverse effects of oral iron administration such as gastrointestinal symptoms. Although saccharated ferric iron oxide had been the only available IV iron formulation in Japan for a long time, ferric carboxymaltose (FCM) has recently been approved. In this review, the characteristics, efficacy, and safety of FCM will be discussed mainly by introducing the results of three clinical trials for FCM conducted in Japan. More effective treatment for patients with IDA might be achieved through the introduction of FCM administration in clinical settings.

Addition of wheat straw to acid sulfate soils with different clay contents reduces acidification in two consecutive submerged-moist cycles

Acid sulfate soils (ASS) are wide-spread in wetlands and experience distinct biogeochemical changes during submerged and moist periods. During submerged periods, under reducing conditions, sulfate reduction can result in a pH increase whereas moist periods induce sulfide and ferrous iron oxidation, leading to acidification which can pose a threat to the environment. A laboratory incubation experiment was carried out to determine the effect of organic matter (OM) amendment on pH and redox potential over two successive submerged-moist cycles in different types of ASS (Sulfuric, Hypersulfidic and two Hyposulfidic soils). The four soils also differed in clay content (10, 15, 23, 38% referred to as C10, C15, C23 and C38) and were collected in a wetland at Banrock Station, South Australia. The experiment was conducted over 24 weeks with each submerged and each moist period lasting 6 weeks. The soils were unamended or amended with 10 g C kg−1 finely ground wheat straw. During the submerged periods, the soils were maintained under a layer of water, in the moist periods they were kept at 100% of water holding capacity. The soil pH increased in both submerged periods, particularly in amended soils with low clay content (C10 and C15). Changes in pH during submerged and moist periods were greater in soils with low clay content (C10, C15) than those with high clay content (C23, C38). The effect of wheat straw addition on pH at the end of submerged and moist periods did not differ between the two submerged-moist periods, with a higher pH in amended than unamended soils. In submerged periods, the redox potential (Eh) decreased more strongly in amended soils than in unamended soils. It was 100–200 mV from week 2 onwards in amended soils whereas the Eh was 300 to 400 mV higher without amendment except in C38 where it was 100–200 mV in both amendment treatments. In the moist periods, the pH decreased more strongly in amended than in unamended soils, particularly in C10 and C15 but remained higher than in unamended treatments. This study showed that wheat straw addition maintains its ameliorative effect on soil pH for at least two submerged-moist cycles, but the ameliorative pH effect depends on clay content, being greater in soils with low clay content.