Insoluble Iron Research Articles

Mobilization of soil-borne arsenic by three common organic acids: Dosage and time effects

A batch experiment was conducted to investigate the mobilization of soil-borne arsenic by three common low-molecular-weight organic acids with a focus on dosage and time effects. The results show that oxalic acid behaved differently from citric acid and malic acid in terms of mobilizing As that was bound to iron compounds. At an equivalent molar concentration, reactions between oxalic acid and soil-borne Fe were kinetically more favourable, as compared to those between either citric acid or malic acid and the soil-borne Fe. It was found that reductive dissolution of soil-borne Fe played a more important role in liberating As, as compared to non-reductive reactions. Prior to the 7th day of the experiment, As mobility increased with increasing dose of oxalic acid while there was no significant difference (P > 0.05) in mobilized As among the treatments with different doses of citric acid or malic acid. The dosage effect on soil-borne As mobilization in the citric acid and malic acid treatments became clear only after the 7th day of the experiment. Soluble Ca present in the soils could cause re-immobilization of As by competing with solution-borne Fe for available organic ligands to form practically insoluble organic compounds of calcium (i.e. calcium oxalate). This resulted in transformation of highly soluble organic complexes of iron (i.e. iron oxalate complexes) into slightly soluble organic compounds of iron (i.e. iron oxalate) or free ferric ion, which then reacted with the solution-borne arsenate ions to form practically insoluble iron arsenates in the latter part of the experiment.

Electrochemical Characterization of a Novel Exoelectrogenic Bacterium Strain SCS5, Isolated from a Mediator-Less Microbial Fuel Cell and Phylogenetically Related to Aeromonas jandaei.

A facultative anaerobic bacterium, designated as strain SCS5, was isolated from the anodic biofilm of a mediator-less microbial fuel cell using acetate as the electron donor and α-FeOOH as the electron acceptor. The isolate was Gram-negative, motile, and shaped as short rods (0.9–1.3 μm in length and 0.4–0.5 μm in width). A phylogenetic analysis of the 16S rRNA, gyrB, and rpoD genes suggested that strain SCS5 belonged to the Aeromonas genus in the Aeromonadaceae family and exhibited the highest 16S rRNA gene sequence similarity (99.45%) with Aeromonas jandaei ATCC 49568. However, phenotypic, cellular fatty acid profile, and DNA G+C content analyses revealed that there were some distinctions between strain SCS5 and the type strain A. jandaei ATCC 49568. The optimum growth temperature, pH, and NaCl (%) for strain SCS5 were 35°C, 7.0, and 0.5% respectively. The DNA G+C content of strain SCS5 was 59.18%. The isolate SCS5 was capable of reducing insoluble iron oxide (α-FeOOH) and transferring electrons to extracellular material (the carbon electrode). The electrochemical activity of strain SCS5 was corroborated by cyclic voltammetry and a Raman spectroscopic analysis. The cyclic voltammogram of strain SCS5 revealed two pairs of oxidation-reduction peaks under anaerobic and aerobic conditions. In contrast, no redox pair was observed for A. jandaei ATCC 49568. Thus, isolated strain SCS5 is a novel exoelectrogenic bacterium phylogenetically related to A. jandaei, but shows distinct electrochemical activity from its close relative A. jandaei ATCC 49568.

Sedimentary Sulphur:Iron Ratio Indicates Vivianite Occurrence: A Study from Two Contrasting Freshwater Systems.

An increasing number of studies constrain the importance of iron for the long-term retention of phosphorus (P) under anoxic conditions, i.e. the formation of reduced iron phosphate minerals such as vivianite (Fe3(PO4)2⋅8H2O). Much remains unknown about vivianite formation, the factors controlling its occurrence, and its relevance for P burial during early sediment diagenesis. To study the occurrence of vivianite and to assess its relevance for P binding, surface sediments of two hydrologically contrasting waters were analysed by heavy-liquid separation and subsequent powder X-ray diffraction. In Lake Arendsee, vivianite was present in deeper sediment horizons and not in the uppermost layers with a sharp transition between vivianite and non-vivianite bearing layers. In contrast, in lowland river Lower Havel vivianite was present in the upper sediment layers and not in deeper horizons with a gradual transition between non-vivianite and vivianite bearing layers. In both waters, vivianite occurrence was accompanied by the presence of pyrite (FeS2). Vivianite formation was favoured by an elevated iron availability through a lower degree of sulphidisation and was present at a molar ratio of total sulphur to reactive iron smaller than 1.1, only. A longer lasting burden of sediments by organic matter, i.e. due to eutrophication, favours the release of sulphides, and the formation of insoluble iron sulphides leading to a lack of available iron and to less or no vivianite formation. This weakening in sedimentary P retention, representing a negative feedback mechanism (P release) in terms of water quality, could be partly compensated by harmless Fe amendments.

Preparation of iron bound succinylated milk protein concentrate and evaluation of its stability

Major problems associated with the fortification of soluble iron salts include chemical reactivity and incompatibility with other components. Milk protein concentrate (MPC) are able to bind significant amount of iron due to the presence of both casein and whey protein. MPC in its native state possess very poor solubility, therefore, succinylated derivatives of MPC (succ. MPC) were also used for the preparation of protein–iron complex. Preparation of the complex involved centrifugation (to remove insoluble iron), ultrafiltration (to remove unbound iron) and lyophilisation (to attain in dry form). Iron binding ability of MPC enhanced significantly (P<0.05) upon succinylation. Stability of bound iron from both varieties of complexes was monitored under different conditions encountered during processing. Higher stability (P<0.05) of bound iron was observed in succ. MPC–iron complex than native protein complex. This method could be adopted for the production of stable iron enriched protein, an organic iron source.

The Phytosiderophore Efflux Transporter TOM2 Is Involved in Metal Transport in Rice

Iron is an essential metal element for all living organisms. Graminaceous plants produce and secrete mugineic acid family phytosiderophores from their roots to acquire iron in the soil. Phytosiderophores chelate and solubilize insoluble iron hydroxide in the soil. Subsequently, plants take up iron-phytosiderophore complexes through specific transporters on the root cell membrane. Phytosiderophores are also thought to be important for the internal transport of various transition metals, including iron. In this study, we analyzed TOM2 and TOM3, rice homologs of transporter of mugineic acid family phytosiderophores 1 (TOM1), a crucial efflux transporter directly involved in phytosiderophore secretion into the soil. Transgenic rice analysis using promoter-β-glucuronidase revealed that TOM2 was expressed in tissues involved in metal translocation, whereas TOM3 was expressed only in restricted parts of the plant. Strong TOM2 expression was observed in developing tissues during seed maturation and germination, whereas TOM3 expression was weak during seed maturation. Transgenic rice in which TOM2 expression was repressed by RNA interference showed growth defects compared with non-transformants and TOM3-repressed rice. Xenopus laevis oocytes expressing TOM2 released (14)C-labeled deoxymugineic acid, the initial phytosiderophore compound in the biosynthetic pathway in rice. In onion epidermal and rice root cells, the TOM2-GFP fusion protein localized to the cell membrane, indicating that the TOM2 protein is a transporter for phytosiderophore efflux to the cell exterior. Our results indicate that TOM2 is involved in the internal transport of deoxymugineic acid, which is required for normal plant growth.

Biofilm formation by groundwater microbial complexes in vitro

The influence of natural organic substances and iron hydroxides on in vitro biofilm formation by groundwater microorganisms was assessed. The combination of these compounds stimulates the formation of large mucosal biofilms that absorb insoluble iron hydroxide particles. Organic substances are important regulators of biofilm formation. Therefore, the location of biofilms in pore space increases the risks of biocolmatage of this space.

Preparation of succinylated sodium caseinate–iron complex by adopting ultrafiltration technology: A novel food fortificant

Abstract Iron has several functions in the human body and its deficiency leads to severe health problems. Food fortification is considered as the most acceptable strategy to combat iron deficiency, but the fortification of soluble iron salts induces many technological problems. Succinylated milk proteins can bind sufficient amount of iron. Many varieties of iron protein succinylates are also available in the market as iron supplements, not as food fortificants. Therefore, the present study was intended to prepare succinylated sodium caseinate (succ. NaCas)–iron complex suitable for food fortification purposes by adopting ultrafiltration technology. Level of iron required for the preparation of complex was standardized on the basis of maximum iron binding ability of succ. NaCas. Diafiltration carried out during the manufacturing process not only removed free iron but also reduced excess succinic acid from the complex. The obtained complex also showed better stability under different conditions encountered during processing. Industrial relevance Centrifugation and ultrafiltration (UF) technologies were adopted in the study, the former used to remove the insoluble iron and latter was used to remove free iron. The presence of both insoluble and free iron may be unacceptable for the food processing. The freeze drying technology was also used to facilitate the availability of iron protein succinylate in the powder form for wide range of food application. The proposed method will help industries to adopt the suitable conditions to produce a novel food fortificant commercially.

The role of additives in moderating the influence of Fe(III) and Cu(II) on the radiochemical yield of [68Ga(DOTATATE)

[68Ga(DOTATATE)] has demonstrated its clinical usefulness. Both Fe3+ and Cu2+, potential contaminants in Gallium-68 generator eluent, substantially reduce the radiochemical (RC) yield of [68Ga(DOTATATE)] if the metal/ligand ratio of 1:1 is exceeded. A variety of compounds were examined for their potential ability to reduce this effect. Most had no effect on RC yield. However, addition of phosphate diminished the influence of Fe3+ by likely forming an insoluble iron salt. Addition of ascorbic acid reduced Cu2+ and Fe3+ to Cu+ and Fe2+ respectively, both of which have limited impact on RC yields. At low ligand amounts (5nmol DOTATATE), the addition of 30nmol phosphate (0.19mM) increased the tolerance of Fe3+ from 4nmol to 10nmol (0.06mM), while the addition of ascorbic acid allowed high RC yields (>95%) in the presence of 40nmol Fe3+ (0.25mM) and 100nmol Cu2+ (0.63mM). The effect of ascorbic acid was highly pH-dependant, and gave optimal results at pH 3.

Accurate mass MS/MS/MS analysis of siderophores ferrioxamine B and E1 by collision-induced dissociation electrospray mass spectrometry.

Siderophores are bacterially secreted, small molecule iron chelators that facilitate the binding of insoluble iron (III) for reuptake and use in various biological processes. These compounds are classified by their iron (III) binding geometry, as dictated by subunit composition and include groups such as the trihydroxamates (hexadentate ligand) and catecholates (bidentate). Small modifications to the core structure such as acetylation, lipid tail addition, or cyclization, make facile characterization of new siderophores difficult by molecular ion detection alone (MS(1)). We have expanded upon previous fragmentation-directed studies using electrospray ionization collision-induced dissociation tandem mass spectrometry (ESI-CID-MS/MS/MS) and identified diagnostic MS(3) features from the trihydroxamate siderophore class for ferrioxamine B and E1 by accurate mass. Diagnostic features for MS(3) include C-C, C-N, amide, and oxime cleavage events with proposed losses of water and -CO from the iron (III) coordination sites. These insights will facilitate the discovery of novel trihydroxamate siderophores from complex sample matrices. Graphical Abstract ᅟ.

River-derived humic substances as iron chelators in seawater

The speciation of iron(III) in oxic seawater is dominated by its hydrolysis and sedimentation of insoluble iron(III)-oxyhydroxide. As a consequence, many oceanic areas have very low iron levels in surface seawater which leads to iron deficiency since phytoplankton require iron as a micronutrient in order to grow. Fortunately, iron solubility is not truly as low as Fe(III) solubility measurements in inorganic seawater would suggest, since oceanic waters contain organic molecules which tend to bind the iron and keep it in solution. Various iron-binding organic ligands which combine to stabilize dissolved iron have been detected and thoroughly investigated in recent years. However, the role of iron-binding ligands from terrestrial sources remains poorly constrained. Blackwater rivers supply large amounts of natural organic material (NOM) to the ocean. This NOM (which consists mainly of vascular plant-derived humic substances) is able to greatly enhance iron bioavailability in estuaries and coastal regions, however, breakdown processes lead to a rapid decrease of river-derived NOM concentrations with increasing distance from land. It has therefore been argued that the influence of river-derived NOM on iron biogeochemistry in offshore seawater does not seem to be significant. Here we used a standard method based on 59Fe as a radiotracer to study the solubility of Fe(III)-oxyhydroxide in seawater in the presence of riverine NOM. We aimed to address the question how effective is freshwater NOM as an iron chelator under open ocean conditions where the concentration of land-derived organic material is about 3 orders of magnitude smaller than in coastal regions, and does this iron chelating ability vary between NOM from different sources and between different size fractions of the river-borne NOM. Our results show that the investigated NOM fractions were able to substantially enhance Fe(III)-oxyhydroxide solubility in seawater at concentrations of the NOM ≥5μgL−1. Terrigenous NOM concentrations ≥5μgL−1 are in no way unusual in open ocean surface waters especially of the Arctic and the North Atlantic Oceans. River-derived humic substances could therefore play a greater role as iron carriers in the ocean than previously thought.

Autoclave Leaching of Arsenic from Copper Concentrate and Matte

Results are given for autoclave leaching of concentrates and mattes from polymetal semiproduct melts containing arsenic alongside copper. The possibility is demonstrated of selective copper and arsenic leaching into solution. It is confirmed that with autoclave leaching arsenides are broken down better than for natural arsenic-containing minerals. 83% of fraction 44 μm. In the first stage, concentrate was treated with acidified copper sulfate solution (180°C; original concentration 10 g/dm 3 H 2 SO 4 ; 16% solid fraction of concentrate in pulp; duration 1.5 h). With an increase in copper sulfate consumption from 20 to 43 g/dm 3 (molar ratio Cu:As = 1.2-2.7), the transfer of iron into the solution increased from 22 to 40%, arsenic from 4.4 to 26.3%; and with Cu:As > 2.0, the role of copper sulfate consumption appeared to be insignificant. With an increase in temperature from 140 to 160°C (Cu:As = 1.2; 10 g/dm 3 H 2 SO 4 ; duration 1,5 h), the transfer of arsenic into the solution increased from 20.6 to 31.5% and iron from 27 to 26%; at 180-200°C, the transfer of iron into solution, and espe- cially arsenic, decreased to 22.0 and 5-7%, respectively; the copper content in the final solution was markedly reduced. Phase analysis data for cakes showed that there was a marked increase in the content of chalcosine and iron arsenate. Apparently with an increase in temperature chalcopyrite becomes an active precipitating agent for copper and strengthens hydrolysis of arsenic-containing anions and iron (III) sulfate with the formation of insoluble iron arsenate. Favorable results were not given by an increase in original solution acidity from 5.0.to 53 g/dm 3 H 2 SO 4 (180°C, Cu:As = 2.5, duration 1.5 h), the transfer of iron and arsenic into the solution increased by 7-10%, and the degree of copper deposition decreased by 30%. In balanced tests (160-180°C, Cu:As = 2.7), not more than 40-42% As and 52-56% Fe passed into the solution, and up to 62-70% Cu was precipitated; cake composition, %: 37-40 Cu, 16-18 Fe, 27-29 S, 0.6-0.7 Sn. Thus, during hydrothermal treatment of original concentrate with acidified copper sulfate solution it was impossible to achieve good arsenic extraction

Inhibition Effect of Some Benzotriazole Derivatives on Carbon Steel in 1M H2so4 Medium

The inhibition effect of some benzotriazole derivatives (1-hydroxybenzotriazole, 5-chlorobenzotriazole and 3-amino-5-mercapto-1,2,4-triazole) on the corrosion of two carbon steels (OL 37 and OLC 45) in 1M H2SO4 was studied potentiostatic and potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and metallurgical microscopy techniques. The inhibition activity analysis of these organic inhibitors was made by assuming that the mechanism of inhibition by organic molecules is chemisorptions and that the energetic of the corrosion process per se is unaffected by the addition of substituents on the parent compound. We presume that, these organic inhibitors inhibit corrosion of carbon steel by a protective mechanism, forming insoluble iron complexes and repairing the porous oxide layers. The addition of the organic inhibitors led in all the cases to inhibition of the corrosion process. Polarization curves indicate that they are mixed type of inhibitors. The inhibition efficiency was high in all the studied cases. The corrosion parameters obtained from polarization curves and from EIS spectra are in good concordance and point out the inhibitory action of derivatives benzotriazole. The adsorptions of the organic compounds on the carbon steels surface obeyed Langmuir’s isotherm. The thermodynamic parameters of adsorption enthalpy (ΔH0), adsorption free energy (ΔG0) and adsorption entropy (ΔS0) were calculated. Further characterization using Fourier transform infrared spectroscopy (FT-IR) demonstrates the adsorption of organic inhibitors and the formation of corrosion products on the carbon steels surface. The inhibition process was attributed to the formation of the adsorbed film on the metal surface that protects the metal against corrosive agents. The EIS measurements have confirmed this protection and pointed out the formation of adsorption layers on the electrode surface.

Transgenic petunia with the iron(III)-phytosiderophore transporter gene acquires tolerance to iron deficiency in alkaline environments.

Iron is an essential nutrient for all plants. However, terrestrial plants often suffer from iron deficiency in alkaline soil due to its extremely low solubility. Alkaline soil accounts for about 30% of all cultivated ground in the world. Plants have evolved two distinct strategies, I and II, for iron uptake from the soil. Dicots and non-graminaceous monocots use Strategy I, which is primarily based on the reduction of iron(III) to iron(II) and the uptake of iron(II) by the iron-regulated transporter, IRT1. In contrast, graminaceous plants use Strategy II to efficiently acquire insoluble iron(III). Strategy II comprises the synthesis and secretion of iron-chelating phytosiderophores, such as mugineic acids and the Yellow Stripe 1 transporter proteins of the iron(III)-phytosiderophore complex. Barley, which exhibits the highest tolerance to iron deficiency in alkaline soil among graminaceous plants, utilizes mugineic acids and the specific iron(III)-mugineic acids transporter, HvYS1. In this study, we established the transgenic plant Petunia hybrida, which originally had only Strategy I, by introducing the HvYS1 transporter gene derived from barley. When the transgenic plants were grown hydroponically in media containing the iron(III)-2′-deoxymugineic acid complex, free 2′-deoxymugineic acid and its iron(III) complex were detected in the root extract of the transgenic plant by electrospray ionization-Fourier transform-ion cyclotron resonance mass spectrometry. The growth of the transgenic petunia was significantly better than that of the control host in alkaline conditions. Consequently, the transgenic plant acquired a significantly enhanced tolerance to alkaline hydroponic media in the presence of the iron(III)-2′-deoxymugineic acid complex. Furthermore, the flower color of the transgenic plant deepened. The results showed that iron-phytosiderophore complexes and their transporters can potentially be utilized to overcome the worldwide iron uptake problems to diverse plant species that are found in areas with alkaline conditions.

Mechanisms Involved in Fe(III) Respiration by the Hyperthermophilic Archaeon Ferroglobus placidus

The hyperthermophilic archaeon Ferroglobus placidus can utilize a wide variety of electron donors, including hydrocarbons and aromatic compounds, with Fe(III) serving as an electron acceptor. In Fe(III)-reducing bacteria that have been studied to date, this process is mediated by c-type cytochromes and type IV pili. However, there currently is little information available about how this process is accomplished in archaea. In silico analysis of the F. placidus genome revealed the presence of 30 genes coding for putative c-type cytochrome proteins (more than any other archaeon that has been sequenced to date), five of which contained 10 or more heme-binding motifs. When cell extracts were analyzed by SDS-PAGE followed by heme staining, multiple bands corresponding to c-type cytochromes were detected. Different protein expression patterns were observed in F. placidus cells grown on soluble and insoluble iron forms. In order to explore this result further, transcriptomic studies were performed. Eight genes corresponding to multiheme c-type cytochromes were upregulated when F. placidus was grown with insoluble Fe(III) oxide compared to soluble Fe(III) citrate as an electron acceptor. Numerous archaella (archaeal flagella) also were observed on Fe(III)-grown cells, and genes coding for two type IV pilin-like domain proteins were differentially expressed in Fe(III) oxide-grown cells. This study provides insight into the mechanisms for dissimilatory Fe(III) respiration by hyperthermophilic archaea.

Atmospheric Processing of Combustion Aerosols as a Source of Bioavailable Iron

Atmospheric processing of combustion aerosols may promote transformation of insoluble iron into soluble forms. Here, an explicit scheme for iron dissolution of combustion aerosols due to photochemical reactions with inorganic and organic acids in solution is implemented in an atmospheric chemistry transport model to estimate the atmospheric sources of bioavailable iron. The model results suggest that deposition of soluble iron from combustion sources contributes more than 40% of the total soluble iron deposition over significant portions of the open ocean in the Southern Hemisphere. A sensitivity simulation using half the iron dissolution rate for combustion aerosols results in relatively small decreases in soluble iron deposition in the ocean, compared with the large uncertainties associated with iron solubility at emission. More accurate quantification of the soluble iron burdens near the source regions and the open ocean is needed to improve the process-based understanding of the chemical modification ...

Association between the frequency of meals combining "Shushoku, Shusai, and Hukusai" (Staple food, main dish, and side dish) and intake of nutrients and food groups among Japanese young adults aged 18-24 years: a cross-sectional study.

"Shushoku," "Shusai," and "Hukusai" are staple food, main dish, and side dish, respectively. The recommended meal in Japan is a combination of "Shushoku," "Shusai," and "Hukusai"; however, it remains unclear whether there is an association between the frequency of these meals and intake of nutrients and food groups. This cross-sectional study examined the association between the frequency of meals combining "Shushoku, Shusai, and Hukusai" and intake of nutrients and food groups among 664 Japanese young adults aged 18-24 y. The dietary habits of the subjects during the preceding month were assessed using a validated brief-type self-administered diet history questionnaire. The frequency of meals combining "Shushoku, Shusai, and Hukusai" was self-reported according to four categories: "less than 1 d or 1 d/wk," "2 or 3 d/wk," "4 or 5 d/wk," and "every day." In both women and men, there was an association between the higher frequency of these meals and higher intake of the following food groups: pulses, green and yellow vegetables, other vegetables, mushrooms, seaweeds, fish and shellfish, and eggs. Moreover, there was an association with higher intake of protein, polyunsaturated fat, n-6 and n-3 polyunsaturated fat, total dietary fiber, soluble and insoluble dietary fiber, β-carotene, α-tocopherol, vitamin K, thiamin, riboflavin, folate, pantothenic acid, vitamin C, potassium, calcium, magnesium, iron, and copper, and lower intake of carbohydrate in both women and men. Our findings support the hypothesis that the meals combining "Shushoku, Shusai, and Hukusai" may be associated with intake of many food groups and nutrients among Japanese young adults.

Effect of Iron Nanoparticles Synthesized by a Sol-Gel Process on &amp;lt;i&amp;gt;Rhodococcus erythropolis&amp;lt;/i&amp;gt; T902.1 for Biphenyl Degradation

Nanoparticles (NPS) are considered as a new generation of compounds to improve environmental remediation and biological processes. The aim of this study is to investigate the effect of iron NPS encapsulated in porous silica (SiO2) on the biphenyl biodegradation by Rhodococcus erythropolis T902.1 (RT902.1). The iron NPS (major iron oxide FexOy form) were dispersed in the porosity of a SiO2 support synthesized by sol-gel process. These Fe/SiO2 NPS offer a stimulating effect on the biodegradation rate of biphenyl, an organic pollutant that is very stable and water-insoluble. This positive impact of NPS on the microbial biodegradation was found to be dependent on the NPS concentration ranging from 10-6 M to 10-4 M. After 18 days of incubation the cultures containing NPS at a concentration of 10-4 M of iron improved RT902.1 growth and degraded 35% more biphenyl than those without NPS (positive control) or with the sole SiO2 particles. Though the microorganism could not interact directly with the insoluble iron NPS, the results show that about 10% and 35% of the initial 10-4 M iron NPS encapsulated in the SiO2 matrix would be incorporated inside or adsorbed on the cell surface respectively and 35% would be released in the supernatant. These results suggest that RT902.1 would produce siderophore-like molecules to attract iron from the porous silica matrix.

Inhibition of Splicing Factor SF3B1: Evaluating Effects on Iron Metabolism in K562 and CD34+ Cells

Somatic mutations in the RNA splicing factor SF3B1 have been found in hematopoietic cells from patients with myelodysplastic syndrome. The association is particularly strong for patients with anemia with ringed sideroblasts, where 65 - 75 % show alterations in SF3B1. Ringed sideroblasts are erythroid precursors with insoluble iron aggregates in mitochondria and deficient hemoglobin synthesis. Thus these cells demonstrate a defect in iron metabolism. SF3B1 is a core component of the U2 snRNP spliceosome, responsible for the majority of mRNA maturation, raising the question of how alteration of SF3B1 might perturb cellular iron metabolism. Meayamycin B, a synthetic analog of the natural product FR901464, is an inhibitor of SF3B1, and here we describe the effects of this compound on cellular iron metabolism in the K562 leukemic cell line and in CD34+ cells isolated from cord blood.Inhibition of SF3B1 by meayamycin B was confirmed by analysis of spliced forms of Mcl-1 mRNA, a known target of SF3B1. In untreated cells, a long form (Mcl-lL) arises from inclusion of exon 2 in the final mRNA. In treated cells, inhibition of SF3B1 splicing generates a short form (Mcl-lS) that lacks exon 2. In the presence of 3 to 10 nM meayamycin B the short splice-form (Mcl-1S) became the dominant species. To examine the effect of inhibition of SF3B1 on iron metabolism, K562 cells were exposed to meayamycin B for 24 hours, with controls of 50 µM hemin and 50 µM deferoxamine (DFO). Steady state mRNA levels of transferrin receptor (TFR-1), ABCB7 (mutations in which are associated with inherited sideroblastic anemia and ataxia), and NDRG1 (n-myc downstream regulated gene, previously shown to be induced by DFO) were significantly down regulated by meayamycin B, as determined by qRT-PCR. NDUFS8 mRNA that encodes a subunit of mitochondrial complex 1 and has previously been shown to be iron-responsive, did not change in response to meayamycin B, hemin, or DFO. However, MRLP19 that encodes a mitochondrial ribosomal component, was strongly down-regulated by meayamycin B. In contrast, cytosolic ribosomal protein RPLP0 was not affected by meayamycin B, hemin or DFO and was used as the endogenous control.Analysis of protein levels by western blotting indicated that meayamycin B increased levels of ferritin (heavy chain) and decreased TFR-1. In concordance with the decreased TFR-1 protein levels, meayamycin B treated K562 cells exhibited significant downregulation of iron uptake from 55Fe-transferrin, similar to that observed for hemin treated cells. DFO treatment significantly increased transferrin iron uptake, compared to untreated controls.A similar set of experiments was performed with CD34+ cells, before or after differentiation with erythropoietin. Meayamycin was efficacious in these cells, as shown by disappearance of the long splice-form Mcl-lL and appearance of the short splice form Mcl-1S in cells exposed to the compound for 16 h. TFR-1 mRNA exhibited a dose dependent decrease in response to meayamycin (both pre and post epo treatment). Neither hemin nor DFO altered TFR-1 mRNA levels, or protein levels. In non-epo treated CD34+ cells, exposure to meayamycin caused a small decrease in ferritin protein levels, but ferritin protein increased in epo-treated cells exposed to meayamycin. Hemin increased ferritin protein in both non-epo and epo treated cells. Mitochondrial ribosomal protein MRPL19 RNA was significantly decreased by meayamycin in all cases, but cytoplasmic ribosomal protein RPLP0 was unaffected by meayamycin. Ribosomal protein levels were not responsive to iron manipulations with hemin or DFO.To summarize, treatment of cells with meayamycin B inhibits SF3B1 function in K562 cells or CD34+ cells. The effects are quicker and cleaner than siRNA, making possible closer functional correlations. Meayamycin treated K562 cells exhibited downregulation of TFR-1 and TFR-1 iron uptake, as if they were sensing high cellular iron levels. Note that this is the opposite of the expected result, because iron loading in the setting of sideroblastic anemia would be expected to be associated with increased cellular iron uptake. In CD34+ cells, a similar downregulation of TFR-1 levels was observed, although iron uptake has not yet been directly measured. The strong decrease in mitochondrial ribosomal protein expression indicates a specific mitochondrial effect of SF3B1 inhibition, which may be an important mediator of iron metabolism. DisclosuresNo relevant conflicts of interest to declare.

Fish kill caused by aluminium and iron contamination in a natural pond used for fish rearing: a case report

Contamination of Pansky Pond, in March 2013, with 119 mg/l aluminium, and 87 mg/l iron by acidic (pH 3.17) inflow from a nearby quarry caused fish die-off, while exhibiting symptoms of suffocation. Transformation of soluble forms of aluminium and iron into insoluble forms occurred on fish gill where the content of aluminium and iron was 100-fold and 12-fold, respectively, that found in control fish in an unaffected pond. In addition to insoluble aluminium and iron, gills showed presence of iron bacteria. Histopathology was characterised by expression of reactive processes and regressive alterations resulting in gill tissue necrosis. Impairment of the excretory function of gills was reflected in significantly (P &amp;lt; 0.01) higher concentrations of ammonia in the blood plasma of exposed fish compared to the control. Damage to parenchymatous tissues (kidney, liver, spleen) of the exposed fish was manifested as dystrophic alterations, higher aluminium and iron content, and enhanced activity of transaminases in blood plasma compared to the control.

Functional role of PilA in iron acquisition in the cyanobacterium Synechocystis sp. PCC 6803.

Cyanobacteria require large quantities of iron to maintain their photosynthetic machinery; however, in most environments iron is present in the form of insoluble iron oxides. Whether cyanobacteria can utilize these sources of iron, and the potential molecular mechanisms involved remains to be defined. There is increasing evidence that pili can facilitate electron donation to extracellular electron acceptors, like iron oxides in non-photosynthetic bacteria. In these organisms, the donation of electrons to iron oxides is thought to be crucial for maintaining respiration in the absence of oxygen. Our study investigates if PilA1 (major pilin protein) may also provide a mechanism to convert insoluble ferric iron into soluble ferrous iron. Growth experiments supported by spectroscopic data of a strain deficient in pilA1 indicate that the presence of the pilA1 gene enhances the ability to grow on iron oxides. These observations suggest a novel function of PilA1 in cyanobacterial iron acquisition.