Natural Iron Research Articles

The Photocatalytic Degradation of Enrofloxacin Using an Ecofriendly Natural Iron Mineral: The Relationship Between the Degradation Routes, Generated Byproducts, and Antimicrobial Activity of Treated Solutions

The use of ecofriendly natural minerals in photocatalytic processes to deal with the antimicrobial activity (AA) associated with antibiotics in aqueous systems is still incipient. Therefore, in this work, the capacity of a natural iron material (NIM) in photo-treatments, generating reactive species, to remove the antibiotic enrofloxacin and decrease its associated AA from water is presented. Initially, the fundamental composition, oxidation states, bandgap, point of zero charge, and morphological characteristics of the NIM were determined, denoting the NIM’s feasibility for photocatalytic processes. Consequently, the effectiveness of different advanced processes such as using solar light with the NIM (Light–NIM) and solar light with the NIM and H2O2 (Light–NIM–H2O2) to reduce AA was evaluated. The NIM acts as a semiconductor under solar light, effectively degrading enrofloxacin (ENR) and reducing its AA, although complete elimination was not achieved. The addition of hydrogen peroxide (NIM–Light–H2O2) enhanced the generation of reactive oxygen species (ROS), thereby increasing the elimination of ENR and AA. The role of ROS, specifically O2•− and HO●, in the degradation of enrofloxacin was distinguished using scavenger species and electron paramagnetic resonance (EPR) analysis. Additionally, the five primary degradation products generated during the advanced processes were elucidated. Furthermore, the relationship between the structure of these products and the persistence or elimination of AA, which was differentiated against E. coli but not against S. aureus, was discussed. The effects of the matrix during the process and the extent of the treatments, including their capacity to promote disinfection, were also studied. The reusability of the natural iron material was examined, and it was found that the NIM–Light–H2O2 system showed an effective reduction of 5 logarithmic units in microbiological contamination in an EWWTP and can be reused for up to three cycles while maintaining 100% efficiency in reducing AA.

Renewable Water Filtration Innovation From Palm Oil Mill Effluent Waste

Indonesia is the largest palm oil producing country in the world. According to data from the North Sumatra BPS in 2021, Palm Oil production was 5,311,884 tons. Every palm oil factory disposes of its liquid waste which results in waste pollution becoming a very crucial issue to be addressed immediately because it has many negative impacts. POME is rich in minerals and carbon, but POME waste is currently not fully utilized optimally. The purpose of this research is to produce the latest innovation in water filtration to realize SDGs 2045 on clean water and sanitation and to study the effectiveness of magnetic which will be applied as clean water filtration by utilizing POME waste and natural sand containing ?-Fe2O3, alumina (Al2O3) and magnetic minerals with well water as samples in this study. The combination of POME waste and natural sand with chemical synthesis and calcination methods at a temperature of 500oC as activation of activated carbon and magnetic metals. The results of the synthesis of POME and natural iron sand obtained solids in the form of black powder. In the VSM test, the magnetization versus magnetic field data of Fe3O4/activated carbon POME obtained a magnetic saturation value of 10.13 emu/g. In the XRD test results of activated carbon materials, composites of activated carbon iron oxide and iron oxide and the synthesis results have diffraction patterns similar to the XRD database from JCPDS and in the COD and BOD tests, it proves a decrease in COD and BOD levels in well water before and after filtration with a large range, this indicates the success of the filtration process. In the AAS test as an identification of Fe metal in well water samples, Fe metal becomes <0.00206 (mg/L) starting from 0.01 (mg/L).

Natural pyrite-zero valent iron enhanced electrocoagulation coupled adsorption system for arsenic oxidation and removal: the efficiency and mechanism study

Natural pyrite-zero valent iron enhanced electrocoagulation coupled adsorption system for arsenic oxidation and removal: the efficiency and mechanism study

Therapeutic potential of synthetic and natural iron chelators against ferroptosis.

Ferroptosis, a regulated form of cell death, is characterized by iron accumulation that results in the production of reactive oxygen species. This further causes lipid peroxidation and damage to the cellular components, eventually culminating into oxidative stress. Recent studies have highlighted the pivotal role of ferroptosis in the pathophysiological development and progression of various diseases such as β-thalassemia, hemochromatosis, and neurodegenerative disorders like AD and PD. Extensive efforts are in progress to understand the molecular mechanisms governing the role of ferroptosis in these conditions, and chelation therapy stands out as a potential approach to mitigate ferroptosis and its related implications in their development. There are currently both synthetic and natural iron chelators that are being researched for their potential as ferroptosis inhibitors. While synthetic chelators are relatively well-established and studied, their short plasma half-life and toxic side effects necessitate the exploration and identification of natural products that can act as efficient and safe iron chelators. In this review, we comprehensively discuss both synthetic and natural iron chelators as potential therapeutic strategies against ferroptosis-induced pathologies.

Hot spot volcano emissions as a source of natural iron fertilization in the ocean

Dust deposition, river runoff and glacial melt are the main sources of trace metals to the surface ocean. In the Canary Islands, deposition is dominated by dry dust deposition from the Saharan desert. However, during 85 days, from 19 September to 13 December 2021, the main source of trace metals on the island of La Palma changed drastically. The eruption of the Tajogaite volcano released tonnes of volcanic ash. Concurrently, several lava flows reached the coastal waters. Volcanic activity on land became the main source of iron (Fe) into the coastal waters. Fe concentrations in seawater reached over 1900 nmol L−1. ∼99 % of the iron was found in the particulate phase (particles >0.2 μm wide; 1920 ± 50 nmol L−1). Colloids, smaller size particles (0.02 μm < colloids < 0.2 μm) represented ∼0.7 % of the iron pool (14.5 ± 0.5 nmol L−1). While the truly soluble phase represented ∼0.03 %. However, the soluble phase presented concentrations reaching 0.66 ± 0.05 nmol L−1, which is ∼10 times higher than generally found in open Atlantic Ocean waters. The results show how the Fe size fractionation evolved during the eruption, from a dominance of large particle phases to smaller-sized compounds.

Edible ultrasmall polyphenolic nanozymes for oral treatment of alcohol-induced acute gastritis

Excessive alcohol consumption and prolonged administration of non-steroidal anti-inflammatory drugs (NSAIDs) lead to gastritis which affects millions globally, yet safe and effective treatment options remain limited. While a range of nanozymes have been employed in the oral treatment of inflammatory bowel disease (IBD), the research directed toward gastritis therapy remains unexplored. The challenges of rapid gastric emptying, harsh gastric acid erosion, and the non-edible ingredient constitution hinder the practical use of nanozymes in this context. Herein, three types of sub-10 nm ultrasmall iron-polyphenol nanozymes (UIPNs) were synthesized by using fully edible natural active polyphenols, iron ions and PVP. UIPNs rapidly penetrated the gastric mucosa, resided in the stomach for over 12 h, and remained stable in the harsh acidic environment. They exhibited excellent enzyme-like activities of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD). Compared to omeprazole, all three types of UIPNs showed superior activity, with Fis UIPNs demonstrating the best performance in preventing and protecting against alcohol-induced gastric mucosal injury in mice. The fully food-sourced components, constructed into ultrasmall nanozymes via non-covalent interactions, ensure long-term safety and hold promise for playing significant roles in various gastrointestinal diseases.

Promoting proximity to enhance Fe-Ca interaction for efficient integrated CO2 capture and hydrogenation

Integrated CO2 capture and utilization (ICCU) using “capture-conversion” dual functional materials (DFMs) paves a cost-effective path for restricting CO2 emissions by eliminating the energy-intensive intermediate processes. The interactions between catalysts and absorbents are believed pivotal in ICCU; however, there is a lack of environment-friendly strategy to fabricate the interaction for industrial applications. Here, we propose a solvent-free mechanochemical approach to promote the interaction by improving the proximity between natural calcium and iron sources. The interaction was systemically investigated and confirmed using XRD, XPS, TEM, TPR, etc. As a result, the mechanochemical approach derived DFM achieved 5.5 mmol g−1 CO2 capacity, 87 % CO2 conversion, and 100 % CO selectivity at 650 °C, significantly outperforming the CaO-alone benchmark (CO2 capacity < 4.5 mmol g−1, CO2 conversion < 73 %). Further incorporating MgO would alleviate the sintering and promote the CO2 capture stability (< 15 % decrease after 20 cycles) by acting as a thermal-stable barrier. Based on in situ XRD, it is further confirmed that Fe-Ca interaction exhibits a dynamic looping mechanism in ICCU. The techno-economic analysis strongly supports the superiority of ICCU catalyzed by naturally sourced DFMs on eliminating the energy and H2 consumption for CO2 capture and upgradation. As a result, producing CO via ICCU using mechanochemical derived DFMs exhibits 20 % and 10 % cost decrease compared to the conventional CCU and ICCU using CaO alone scenarios, pointing out the potential of ICCU technology in industrial applications.

Transformation of iron-minerals from natural aquifer media by sulfate-reducing bacteria: Behavior, mechanism, and Cr(VI) removal

Sulfate-reducing bacteria (SRB) and iron minerals are widespread in subsurface environments, where their mediated Fe and S transformations are crucial for contaminant immobilization. However, the mechanism mediated by SRB to transform natural iron minerals into reduced iron–sulfur compounds and the contaminant removal capacity of the transformation products remain unclear. Herein, the mechanism of native SRB-mediated transformation of iron-minerals from natural aquifer media into biogenic ferrous sulfide (FeS) was revealed and the Cr(VI) removal performance of the transformation product was evaluated. The results showed that Fe2+ production, sulfate reduction, and sulfide production occurred sequentially (rather than simultaneously) in the liquid phase. This suggests new processes and mechanisms for iron-mineral transformation: first, iron minerals dissolve to produce Fe2+ under enzymatic action rather than sulfide reduction; then, the generated Fe2+ accelerates sulfate reduction by SRB, producing sulfide in large amounts; finally, sulfide combines rapidly with Fe2+ to produce FeS. Elevated temperatures markedly shortened the required transformation time to start: maximum Fe production occurred at 18–24 days, 6–12 days, and 0–6 days at 10 °C, 20 °C, and 35 °C, respectively. Ambient temperature strongly affected SRB community composition, with Desulfosporosinus dominant at 10 °C and 20 °C and Desulfotomaculales prevalent at 35 °C. Sequential extraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analyses confirmed FeS as the main transformation product, which exhibited a highly efficient Cr(VI) removal capacity. Extending transformation time or increasing transformation temperature enhanced the Cr(VI) removal capacity of the transformation product. In column experiments, in-situ stimulation of SRB growth in aquifer media is able to form FeS, the Cr(VI) removal capacity of FeS reached up to 90.1 mg(Cr(VI))/kg(media). These findings suggest that biostimulation of SRB to mediate the in-situ transformation of iron-minerals to FeS has great potential for remediation of contaminated groundwater.

Glacial interglacial variations in the natural iron fertilization during the low sea ice periods along the eastern continental margin of Antarctica

The Southern Ocean sequesters atmospheric CO2 through biological pumps, though its driving factors are debated. Modern productivity is regulated by natural iron fertilization from micronutrient influx through dust, regeneration, and Antarctic glaciers and sea ice melting (ice melt). The productivity along the eastern Antarctic continental margin was low during the last glacial period and gradually increased through the deglacial to Late Holocene, marked by distinct productivity peaks. The micronutrients also varied similarly, with reduced glacial influx and an increase in the Holocene, which may cause productivity peaks. Therefore, the coherence of enhanced productivity and micronutrient influx is considered as enhanced iron fertilization period. The productivity peaks declined within ∼1.5 kyr, mostly due to the Ekman transport and sea ice formation. Along with ice melt, the independent weathering pattern that responds with glacial- interglacial ice volume changes suggest the source of micronutrients is not terrigenous. Shelf interaction of oceanic currents can influence the water column nutrient stock significantly, while its utilization occurs during reduced ice periods (low sea ice and high glacier melting) for productivity. Therefore, enhanced natural iron fertilization periods are considered as ice low periods that occurred in a periodicity of 2 kyrs, at ∼7.5 kyr BP, ∼5.5 kyr BP, ∼4 kyr BP, ∼ 2.5 kyr BP, and ∼0.5 kyr BP, likely due to the combined effects of atmospheric and oceanographic factors driven by the high amplitude regional temperature variability during the mid to late Holocene.

Synergistically enhanced heterogeneous activation of dissolved oxygen for aqueous carbamazepine degradation over S(III) coupled with siderite

The wide occurrence of emerging contaminants (ECs) was drawing more attention due to the potential hazard and threat on human and environment. Carbamazepine (CBZ) is a widely prescribed medication that has garnered considerable research interest with the exposures exceeding the environmental carrying capacity. We have established the innovative heterogeneous advanced oxidation process (AOPs) based on the activated dissolved oxygen (DO) coupled with S(III) and natural iron ore (siderite). In S(III)/O2/siderite system, we investigated the degradation efficiency, reactive species generation mechanism, and degradation pathway of CBZ. CBZ degradation and mineralization rate were 90% above and ∼15% with the reaction time of 40 min. The degradation of CBZ conformed to a pseudo-first-order kinetic model, with an activation energy determination of 76.36 kJ/mol. The optimal initial solution pH was the weak acid condition (pH = 4–6) for CBZ degradation. Moreover, the inhibition effects of coexisting substance including Cl−, HCO3−, and natural organic matter (NOM) on CBZ removal were observed, while the coexisted SO42− exhibited no significant influence. In addition, the reactive species generated in S(III)/O2/siderite system were predominantly identified as sulfate radical (SO4∙-) and hydroxyl radical (∙OH). The crucial intermediate complexes, Fe(III)S(IV)O3(+) and Fe(II)HS(IV)O3(+), was proposed to form in the initial stages of the reaction, which upon decomposition, yielded SO4∙- along with other reactive species. The degradation pathway of CBZ primarily involved deamination, oxidative ring-opening, hydroxylation, decarboxylation, and ketone degradation processes. This work provides the effective approach for the CBZ degradation with the mild reaction conditions and the sustainable technology for ECs treatment and control.

ATH434, a promising iron-targeting compound for treating iron regulation disorders.

Cytotoxic accumulation of loosely bound mitochondrial Fe2+ is a hallmark of Friedreich's Ataxia (FA), a rare and fatal neuromuscular disorder with limited therapeutic options. There are no clinically approved medications targeting excess Fe2+ associated with FA or the neurological disorders Parkinson's disease and Multiple System Atrophy. Traditional iron-chelating drugs clinically approved for systemic iron overload that target ferritin-stored Fe3+ for urinary excretion demonstrated limited efficacy in FA and exacerbated ataxia. Poor treatment outcomes reflect inadequate binding to excess toxic Fe2+ or exceptionally high affinities (i.e. ≤10-31) for non-pathologic Fe3+ that disrupts intrinsic iron homeostasis. To understand previous treatment failures and identify beneficial factors for Fe2+-targeted therapeutics, we compared traditional Fe3+ chelators deferiprone (DFP) and deferasirox (DFX) with additional iron-binding compounds including ATH434, DMOG, and IOX3. ATH434 and DFX had moderate Fe2+ binding affinities (Kd's of 1-4 µM), similar to endogenous iron chaperones, while the remaining had weaker divalent metal interactions. These compounds had low/moderate affinities for Fe3+(0.46-9.59µM) relative to DFX and DFP. While all compounds coordinated iron using molecular oxygen and/or nitrogen ligands, thermodynamic analyses suggest ATH434 completes Fe2+ coordination using H2O. ATH434 significantly stabilized bound Fe2+ from ligand-induced autooxidation, reducing reactive oxygen species (ROS) production, whereas DFP and DFX promoted production. The comparable affinity of ATH434 for Fe2+ and Fe3+ position it to sequester excess Fe2+ and facilitate drug-to-protein iron metal exchange, mimicking natural endogenous iron binding proteins, at a reduced risk of autooxidation-induced ROS generation or perturbation of cellular iron stores.

Coupled transformation pathways of iron minerals and natural organic matter related to iodine mobilization in alluvial-lacustrine aquifer

The complex of natural organic matter (NOM) and iron minerals in sediment is the main host and source of groundwater iodine. However, the transformation pathways of the complex remain unclear. The groundwater and sediment from the Hetao Basin were collected in this study to analyze multi-isotopes, NOM molecular characteristics, and iron mineral phases. The results showed that high-iodine groundwater was mainly observed in the discharge area, where biodegradation of NOM, sulfate reduction and methanogenesis occurred. Compared to the shallow clayey sediments, the confined sandy sediments had lower iodine content, a lower fraction of crystalline iron oxides, and a higher fraction of carbonate associated Fe(II) minerals, suggesting that the release of sediment iodine in the aquifer is related to the transformation of sediment Fe(III) hydroxides/oxides. Moreover, the molecular features of high-iodine groundwater NOM and sandy sediment NOM were characterized by a higher proportion of refractory compounds, suggesting that the reductive transformation of sediment Fe(III) hydroxides/oxides is fueled by degradable organic compounds. The microbial Fe-reducing and/or sulfate-reducing processes cause the enrichment of groundwater iodine in the form of iodide via the transformation of iodine species. These findings provide new insights into the genesis of high-iodine groundwater.

Impact of Iron Tablet and Moringa Leaf Capsule Supplementation on Hemoglobin Levels in Anemic Pregnant Women in Pariaman City, 2016

Background: Iron deficiency anemia is a prevalent global nutritional problem, particularly affecting pregnant women in developing countries. This study aimed to evaluate the effects of iron tablet supplementation and Moringa leaf capsules on hemoglobin (Hb) levels in anemic pregnant women in Pariaman City, Indonesia. Method: A total of 60 pregnant women were divided into two groups: one receiving iron tablets and the other Moringa leaf capsules for four weeks. Hemoglobin levels were measured before and after the intervention. Findings: In the iron supplementation group, the average Hb level increased from 9.05 g/dL to 9.46 g/dL, with a significant improvement (p = 0.001). Similarly, the Moringa capsule group showed an Hb increase from 8.99 g/dL to 9.27 g/dL (p = 0.019). While iron tablets resulted in a greater increase in Hb, Moringa capsules, rich in natural iron, also demonstrated significant effectiveness. The study concludes that both iron supplements and Moringa capsules are effective in increasing Hb levels, with Moringa capsules being a potential natural alternative for combating anemia in pregnant women. However, optimizing the dosage of Moringa could further enhance its efficacy. Factors such as adherence, diet, and knowledge of iron absorption enhancers and inhibitors play crucial roles in the success of the interventions.

Life Cycle Analysis Comparison of Stabilizing Materials for Expansive Soils

Expansive soils present significant challenges to infrastructure stability, necessitating the use of stabilizing materials. This study conducts a comprehensive life cycle analysis (LCA) research design to evaluate the environmental sustainability of various stabilizing materials for expansive soil. The study uses a quantitative analysis assessing materials, including cement, limestone, natural pozzolana, iron ore tailings, and geopolymers (especially alkali-activated slag cement). The method involves a comprehensive LCA, considering phases from raw material extraction through production, use, and disposal. The analysis reveals distinct differences in environmental impact. Cement and lime, common stabilizers, show a high carbon footprint. Natural pozzolana and iron ore tailings exhibit potential as supplementary cementitious materials with reduced environmental impact. Geopolymers, particularly alkali-activated slag cement, offer promising alternatives with lower carbon emissions. This research contributes insights into sustainable geotechnical practices, guiding material selection aligned with environmental goals for effective expansive soil stabilization.

Hematite nanomaterial from a tropical freshwater ecosystem: Geological, environmental, and industrial implications

Synthetic hematite (Fe2O3) nanoparticles are extensively explored for medicine, optics, and environmental remediation. However, natural iron nanoparticles in a freshwater ecosystem have not been well characterized. Here we report the presence of natural iron nanoparticles in a tropical freshwater ecosystem in southern India. These iron nanoparticles that exist as slime in the natural water system were characterized through a multiproxy investigation involving Field-Emission Scanning Electron Microscopy (FE-SEM), X-ray Diffraction (XRD), X-ray Fluorescence (XRF), X-ray Photoelectron Spectroscopy (XPS), and Raman spectroscopy and BET analyses. These nanoparticles exist as amorphous hematite (Fe2O3), with the XRD peaks matching that of the iron arsenate compound. Fe2O3 occurs as mesoporous hollow microspheres with a size range of 14.97 to 61.3 nm and a surface area of 48.45m2/g. Further, the identification of Bacillus cereus in the slime suggests its role in iron sequestration, indicating a biogeochemical origin, which we infer is a particularly common phenomenon in tropical river basins where lateritic soils prevail. This study is the first to describe natural iron nanoparticles in a tropical freshwater ecosystem. It identifies their amorphous hematite structure and biogeochemical origin, offering new insights into their ecological roles and potential applications. This discovery presents an opportunity for utilizing this slime as an important source of hematite nanomaterials, with potential industrial applications.

Effect of Fe (III)/Fe (II) cation molar ratio variation on magnetite Fe3O4 nanoparticles synthesized from natural iron sand by co-precipitation method

Effect of Fe (III)/Fe (II) cation molar ratio variation on magnetite Fe3O4 nanoparticles synthesized from natural iron sand by co-precipitation method

Effect of iron minerals on formation of hydroandradite during alkali-thermal process

The hydroandradite (HA) is an efficient and ideal desilication product to deal with the bauxite and red mud based on the alkali-thermal process, while the selection of iron source is crucial for the HA generation. This work investigates the effects of various natural iron minerals on the alkali-thermal formation HA in aluminate solution by comparing with synthetic sodium ferrate. The Gibbs free energy changes of HA formation with different iron oxides were calculated based on the complex silicate theory, and the preferential conversion order for HA formation was obtained thermodynamically. The solubility data of various iron minerals in aluminate solution were determined and correlated by the Apelblat model. The contribution order of iron minerals for HA formation was obtained, and the goethite is the best alternative to replace sodium ferrite by comparing to hematite and magnetite. The phase transformation of HA is above 80% in the presence of goethite, and the alkali content in reaction product is as low as 0.20%. Moreover, the effect mechanism of goethite on HA formation was discussed and established.

Generic phosphate affinity constants of the CD-MUSIC-eSGC model to predict phosphate adsorption and dominant speciation on iron (hydr)oxides

Estimating the availability of phosphorus in soils and sediments is complicated by the diverse mineralogical properties of iron (hydr)oxides that control the environmental fate of phosphorus. Despite various surface complexation models have been developed, lack of generic phosphate affinity constants (logKPO4s) for iron (hydr)oxides hinders the prediction of phosphate adsorption to iron (hydr)oxides in nature. The aim of this work is to derive generic logKPO4s for the Charge Distribution-Multisite Complexation extended-Stern-Gouy-Chapman (CD-MUSIC-eSGC) model using a large phosphate adsorption database and previously derived generic protonation parameters. The optimized logKPO4s of goethite, hematite and ferrihydrite are located in a much narrower range than those in the RES3T database. Specifically, the logKPO4 ranges of FeOPO3, FeOPO2OH, FeOPO(OH)2, (FeO)2PO2, and (FeO)2POOH complexes were 17.40–18.00, 24.20–27.40, 27.90–29.80, 26.50–29.60, and 30.70–33.40, respectively. A simplified CD-MUSIC-eSGC model with species FeOPO2OH and (FeO)2PO2 and generic logKPO4 values 26.0 ± 0.9 and 27.9 ± 0.8, respectively, provides an accurate prediction of phosphate adsorption and dominant speciation to the iron (hydr)oxides at environmental pH and phosphate levels. For ferrihydrite at low pH and high phosphate levels the species FeOPO(OH)2 and (FeO)2POOH cannot be neglected. The simplified model expands the application boundaries of CD-MUSIC-eSGC model in predicting the phosphate adsorption on natural iron (hydr)oxides without laborious characterization.

Strain variation in the Candida albicans iron limitation response.

Iron acquisition is critical for pathogens to proliferate during invasive infection, and the human fungal pathogen Candida albicans is no exception. The iron regulatory network, established in reference strain SC5314 and derivatives, includes the central player Sef1, a transcription factor that activates iron acquisition genes in response to iron limitation. Here, we explored potential variation in this network among five diverse C. albicans strains through mutant analysis, Nanostring gene expression profiling, and, for two strains, RNA-Seq. Our findings highlight four features that may inform future studies of natural variation and iron acquisition in this species. (i) Conformity: In all strains, major iron acquisition genes are upregulated during iron limitation, and a sef1Δ/Δ mutation impairs that response and growth during iron limitation. (ii) Response variation: Some aspects of the iron limitation response vary among strains, notably the activation of hypha-associated genes. As this gene set is tied to tissue damage and virulence, variation may impact the progression of infection. (iii) Genotype-phenotype variation: The impact of a sef1Δ/Δ mutation on cell wall integrity varies, and for the two strains examined the phenotype correlated with sef1Δ/Δ impact on several cell wall integrity genes. (iv) Phenotype discovery: DNA repair genes were induced modestly by iron limitation in sef1Δ/Δ mutants, with fold changes we would usually ignore. However, the response occurred in both strains tested and was reminiscent of a much stronger response described in Cryptococcus neoformans, a suggestion that it may have biological meaning. In fact, we observed that the iron limitation of a sef1Δ/Δ mutant caused recessive phenotypes to emerge at two heterozygous loci. Overall, our results show that a network that is critical for pathogen proliferation presents variation outside of its core functions.IMPORTANCEA key virulence factor of Candida albicans is the ability to maintain iron homeostasis in the host where iron is scarce. We focused on a central iron regulator, SEF1. We found that iron regulator Sef1 is required for growth, cell wall integrity, and genome integrity during iron limitation. The novel aspect of this work is the characterization of strain variation in a circuit that is required for survival in the host and the connection of iron acquisition to genome integrity in C. albicans.

Effect of Al Substitution on Visible Short-Wave Infrared Reflectance Spectroscopy (VSWIR) of Goethite and Ferrihydrite

Goethite and ferrihydrite are the two major iron hydroxides, essential mineral constituents in the terrestrial surface system. Aluminum (Al) is the most common substituent in iron hydroxides, and it may significantly change the bulk and surficial physicochemical properties of iron hydroxides. Consequently, a practical and convenient approach is needed to efficiently identify the Al substitution degrees of iron hydroxides in natural occurrences. This study presents a comprehensive investigation of the VSWIR characteristics of laboratory-synthesized Al-substituted goethite and ferrihydrite, to establish diagnostic VSWIR parameters for the identification and quantification of Al substitution levels in iron hydroxides. The findings revealed that Al substitution can affect the band positions (P) of goethite and ferrihydrite at ~650 nm, ~900 nm, and ~1400 nm. The relationships between the Al substitution of ferrihydrite and VSWIR parameters can be expressed as P900 = −0.43 × Al(%) + 931 and P1400 = −0.07 × Al(%) + 1428, while that of goethite can be expressed as P650 = 0.42 × Al(%) + 657 and P900 = 2.29 × Al(%) + 936. The peak fitting results showed that the absorption intensity at 480–550 nm linearly decreases with increased Al substitution. The obtained VSWIR spectra of Al-substituted goethite and ferrihydrite provide a critical supplement to the spectral library for (Al) iron hydroxides, and these VSWIR parameters can be utilized for the semi-quantitative determination of Al substitution in natural iron hydroxides