Iron-reducing Ability Research Articles

Efficient synthesis and molecular docking of new organoselenium and organosulphur compounds as dual inhibitors for the therapy of Alzheimer's disease as well as Diabetes Mellitus

There are several oxidative stress-related pathways interconnecting Alzheimer's disease and type II diabetes, two public health problems worldwide. Therefore, development of potential multifunctional agents for dual therapy of AD and T2D has received much attention. The present study was aimed to synthesize a new selenocarbonyl and thiocarbonyl compounds and evaluating multifunctional ability of them in the AD and T2D dual therapy. [(PhP(Se)(μ-Se)]2, the selenium counterpart of the well-known sulfur transfer Lawesson's reagent, is a useful reagent for the synthesis of selenocarbonyl compounds. For the conversion of various carbonyl compounds into thiocarbonyl derivatives was formulated by its reaction with LR, [(p-MeOC6H4)P(S)(μ-S)]2. The reactions are carried out under mild conditions and afforded the seleno and thio compounds in good yields. By measuring the newly created compounds' overall antioxidant capacity, iron-reducing ability, and scavenging activity against DPPH and ABTS radicals, they were investigated as antioxidant molecules. Additionally, all the compounds were subjected to further investigation by testing their acetylcholinesterase, α-amylase and α-glucosidase inhibiting activity. According to our findings, the amide derivatives exhibited more promising biological inhibitory actions in comparison to the other compounds. With a total antioxidant capacity (TAC) of 75.11 ± 0.04 mg gallic acid/gm, an iron-reducing power (IRP) of 69.86 ± 0.04 µg/mL, a DPPH radical-scavenging activity (%) of 55.89 ± 0.03 (IC50 = 6.19 ± 0.03 µg/ml), and an ABTS radical-scavenging activity (%) of 61.14 ± 0.03 (IC50 = 4.97 ± 0.06 µg/mL), benzoselenoamide derivative 11b in particular showed the highest antioxidant activities when compared to ascorbic acid. It also affected the activity of acetylcholinesterase through competitive inhibition, which was on par with Donepezil as indicated by in vitro percentage of inhibition 57.44 ± 0.07 % (IC50 = 5.13 ± 0.03 µg/mL). Additionally, it exhibited a comparable level of inhibition to Acarbose in the in vitro percentage of inhibition for α-amylase and α-glucosidase activity, 53.17 ± 0.03 (IC50 = 4.32 ± 0.02) and 42.92 ± 0.03 (IC50 = 2.99 ± 0.02) respectively. Furthermore, molecular docking calculations were made to explain the dual inhibitors for the therapy of Alzheimer's as well as Diabetes Mellitus for all synthesized compounds. In silco docking results revealed that compound 11b were the top docked bioactive compounds against the target proteins (AChE as a cholinergic enzyme and 11-Beta-Hydroxysteroid dehydrogenase-1(11β-HSD1)). After these calculations, ADMET analysis was performed to examine the drug properties of all novel compounds. Overall, the results demonstrated that the organoselenium-based compounds might serve as possible drugs for the therapy of Alzheimer's disease as well as Diabetes Mellitus.

Maribellus mangrovi sp. nov., an iron-reducing bacterium isolated from mangrove sediment.

A novel facultatively anaerobic and Gram-stain-negative bacterium, designated FJH33T, was isolated from mangrove sediment sampled in Zhangzhou, PR China. Cells of strain FJH33T were rod-shaped or slightly curved-shaped, with widths of 0.3-0.5 µm and lengths of 1.0-3.0 µm. Optimum growth of strain FJH33T occurred in the presence of 3 % NaCl (w/v), at 33 °C and at pH 7.0. Oxidase activity was negative, while catalase activity was positive. Its iron-reducing ability was determined. Based on 16S rRNA gene sequence similarity, strain FJH33T was most closely related to Maribellus luteus XSD2T (95.1 %), followed by Maribellus sediminis Y2-1-60T (95.0 %) and Maribellus maritimus 5E3T (94.9 %). Genome analysis of strains FJH33T and M. luteus XSD2T revealed low genome relatedness, with an average nucleotide identity value of 73.8% and a digital DNA-DNA hybridization value of 19.0%. Phylogenetic trees built from 16S rRNA genes and genome sequences showed that strain FJH33T represents a relatively independent phylogenetic lineage within the genus Maribellus. The major cellular fatty acids (≥10 %) were iso-C15 : 0 and C18 : 1 ω9c. The sole respiratory quinone was MK-7. The polar lipids consisted of phosphatidylethanolamine, diphosphatidylcholine, diphosphatidyglycerol and one unidentified lipid. The DNA G+C content was 41.4 mol%. Based on the integrated results of phylogenetic, physiological, biochemical and chemotaxonomic characterizations, we propose that strain FJH33T represents a novel species of the genus Maribellus, for which the name Maribellus mangrovi sp. nov. is proposed. The type strain is FJH33T (=KCTC 102210T=MCCC 1H01459T).

FeS-based cascade bioreactors driven by Shewanella oneidensis MR-1 for efficient chemodynamic therapy with augmented antitumor immunity

Chemodynamic therapy (CDT) is an emerging therapeutic approach, which can trigger immune responses by causing tumor cell death and releasing tumor-associated antigens. However, CDT alone is not effective in eliciting a robust immune response. Herein, FeS nanoparticles are in situ fabricated on the surface of Shewanella oneidensis MR-1 (FeS@MR-1) for enhanced CDT to boost antitumor immunity. Under acidic conditions, FeS@MR-1 degrades and simultaneously induces the release of Fe(II) ions and H2S gas. The released H2S can inhibit the activity of catalase, resulting in the accumulation of H2O2, which facilitates the production of highly toxic hydroxyl radical (·OH) through the Fenton reaction catalyzed by Fe(II). Thanks to the iron-reducing ability during the anaerobic respiration process, S. oneidensis MR-1 drives the Fenton reaction to proceed continuously by promoting Fe(III) to Fe(II) conversion to ensure the high efficiency of CDT. Furthermore, FeS@MR-1 can reprogram the immunosuppressive tumor microenvironment by consuming lactate and act as a natural immune adjuvant to enhance immune responses. More importantly, the combined treatment of FeS@MR-1 with immune checkpoint blockade triggers systemic antitumor responses, leading to excellent therapeutic performance against primary, distant, and orthotopic ovarian tumors. This work presents a cascade bioreactor based on S. oneidensis MR-1, which is promising for enhanced CDT and immunotherapy.

The addition of humic substances extracted from vermicompost enhances the growth performance and the antioxidant status of weaning pigs

The aim of the study was to assess the effect of humic substances (HS) extracted from vermicompost on the growth performance, fecal score, bone ash content and antioxidant status in muscles and blood serum of weaned pigs from 1-42 days postweaning. Two-hundred 22-day weaned pigs were assigned to four treatments: 1= Positive control diet with colistin (PC), 2= Negative control diet without antibiotic or HS (NC), 3 and 4= Diets with 2 500 and 5 000 ppm of HS, respectively. Growth performance, fecal consistency, dry matter and ashes of metatarsus and the 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity, iron reducing ability and thiobarbituric acid reactive substances in muscles and blood were registered. Results were subjected to ANOVA and regression analysis. Linear increasing responses (P < 0.05) were found in the body weight at 42 days postweaning, the ADG from 1-7, 8-21, 22-42 and 1-42 and the gain:feed ratio from 1-7, 22-42 and 1-42 days postweaning, whilst the fecal score decreased linearly (P < 0.01) from 1-7, 8-21 and 1-42 days postweaning due to the increasing dietary HS concentration. The antioxidant potential of 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity (P < 0.05) in loin muscle and blood serum at three and seven days, and in fillet muscle at seven days postweaning increased linearly due to the increasing dietary HS concentration. It is concluded that the addition of HS improved the growth performance from 1-42 days postweaning and the antioxidant status in muscles and blood serum of weaned pigs at three and seven days postweaning.

Iron or sulfur respiration-an adaptive choice determining the fitness of a natronophilic bacterium Dethiobacter alkaliphilus in geochemically contrasting environments.

Haloalkaliphilic microorganisms are double extremophiles functioning optimally at high salinity and pH. Their typical habitats are soda lakes, geologically ancient yet widespread ecosystems supposed to harbor relict microbial communities. We compared metabolic features and their determinants in two strains of the natronophilic species Dethiobacter alkaliphilus, the only cultured representative of the class "Dethiobacteria" (Bacillota). The strains of D. alkaliphilus were previously isolated from geographically remote Mongolian and Kenyan soda lakes. The type strain AHT1T was described as a facultative chemolithoautotrophic sulfidogen reducing or disproportionating sulfur or thiosulfate, while strain Z-1002 was isolated as a chemolithoautotrophic iron reducer. Here, we uncovered the iron reducing ability of strain AHT1T and the ability of strain Z-1002 for thiosulfate reduction and anaerobic Fe(II) oxidation. Key catabolic processes sustaining the growth of both D. alkaliphilus strains appeared to fit the geochemical settings of two contrasting natural alkaline environments, sulfur-enriched soda lakes and iron-enriched serpentinites. This hypothesis was supported by a meta-analysis of Dethiobacterial genomes and by the enrichment of a novel phylotype from a subsurface alkaline aquifer under Fe(III)-reducing conditions. Genome analysis revealed multiheme c-type cytochromes to be the most probable determinants of iron and sulfur redox transformations in D. alkaliphilus. Phylogeny reconstruction showed that all the respiratory processes in this organism are likely provided by evolutionarily related early forms of unconventional octaheme tetrathionate and sulfite reductases and their structural analogs, OmhA/OcwA Fe(III)-reductases. Several phylogenetically related determinants of anaerobic Fe(II) oxidation were identified in the Z-1002 genome, and the oxidation process was experimentally demonstrated. Proteomic profiling revealed two distinct sets of multiheme cytochromes upregulated in iron(III)- or thiosulfate-respiring cells and the cytochromes peculiar for Fe(II) oxidizing cells. We suggest that maintaining high variation in multiheme cytochromes is an effective adaptive strategy to occupy geochemically contrasting alkaline environments. We propose that sulfur-enriched soda lakes could be secondary habitats for D. alkaliphilus compared to Fe-rich serpentinites, and that the ongoing evolution of Dethiobacterales could retrace the evolutionary path that may have occurred in prokaryotes at a turning point in the biosphere's history, when the intensification of the sulfur cycle outweighed the global significance of the iron cycle.

LC-ESI-QTOF-MS/MS Characterization of Phenolic Compounds in Common Commercial Mushrooms and Their Potential Antioxidant Activities

Mushrooms have a long history of use as food and medicine. They are rich in various nutrients and bioactive compounds, particularly phenolic compounds. In this study, ten mushroom species were selected, and solvent extraction using 80% ethanol was used to extract phenolic compounds. Total phenolic content (TPC), total flavonoid content (TFC) and total condensed tannin content (TCT) were measured to evaluate phenolic content in different mushroom varieties. In the mushroom varieties tested, brown portobello mushroom had the highest TPC (396.78 ± 3.12 µg GAE/g), white cup mushroom exhibited the highest TFC (275.17 ± 9.40 μg CE/g), and shiitake mushroom presented the highest TCT (13.80 ± 0.21 µg QE/g). Antioxidant capacity was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), 2,2′-azino-bis-3ethylbenzothiazoline-6-sulfonic acid (ABTS) and total antioxidant capacity (TAC) assays. The highest DPPH free radical scavenging ability was found in white cup mushroom (730.14 ± 55.06 µg AAE/g), while the greatest iron-reducing ability (FRAP) was recorded for shiitake mushroom (165.32 ± 10.21 μg AAE/g). Additionally, Swiss brown mushroom showed the highest ABTS antioxidant capacity (321.31 ± 5.7 μg AAE/g), and the maximum TAC value was found in shiitake mushroom (24.52 ± 1.2 μg AAE/g). These results highlight that most of the mushroom varieties studied showed high phenolic contents and demonstrated strong antioxidant activity, with shiitake mushrooms standing out due to their high TCT and FRAP values, and the highest TAC value among the varieties studied. In addition, LC-ESI-QTOF-MS/MS was used to characterize the mushroom samples, and tentatively identified a total of 22 phenolic compounds, including 11 flavonoids, 4 lignans, 3 phenolic acids, 2 stilbenes and 2 other phenolic compounds in all mushroom samples. The research results of this study showed that mushrooms are a good source of phenolic compounds with strong antioxidant potential. The results can provide a scientific basis for the development of mushroom extracts in functional food, health products, and other industries.

Variation in Phenolic Compounds, Antioxidant and Antibacterial Activities of Extracts from Different Plant Organs of Meadowsweet (Filipendula ulmaria (L.) Maxim.).

Meadowsweet (Filipendula ulmaria (L.) Maxim.) has been widely used in the treatment of various diseases. The pharmacological properties of meadowsweet are derived from the presence of phenolic compounds of a diverse structure in sufficiently large quantities. The purpose of this study was to examine the vertical distribution of individual groups of phenolic compounds (total phenolics, flavonoids, hydroxycinnamic acids, catechins, proanthocyanidins, and tannins) and individual phenolic compounds in meadowsweet and to determine the antioxidant and antibacterial activity of extracts from various meadowsweet organs. It was found that the leaves, flowers, fruits, and roots of meadowsweet are characterized by a high total phenolics content (up to 65 mg g-1). A high content of flavonoids was determined in the upper leaves and flowers (117-167 mg g-1), with high contents of hydroxycinnamic acids in the upper leaves, flowers, and fruits (6.4-7.8 mg g-1); high contents of catechins and proanthocyanidins in the roots (45.1 and 3.4 mg g-1, respectively); and high tannin content in the fruits (38.3 mg g-1). Analysis of extracts by high-performance liquid chromatography (HPLC) showed that the qualitative and quantitative composition of individual phenolic compounds in various parts of the meadowsweet varied greatly. Among the flavonoids identified in meadowsweet, quercetin derivatives dominate, namely quercetin 3-O-rutinoside, quercetin 3-β-d-glucoside, and quercetin 4'-O-glucoside. Quercetin 4'-O-glucoside (spiraeoside) was found only in the flowers and fruits. Catechin was identified in the leaves and roots of meadowsweet. The distribution of phenolic acids across the plant was also uneven. In the upper leaves, a higher content of chlorogenic acid was determined, and in the lower leaves, a higher content of ellagic acid determined. In flowers and fruits, a higher contents of gallic, caftaric, ellagic, and salicylic acids were noted. Ellagic and salicylic acids were also dominant among phenolic acids in the roots. Based on the results of the analysis of antioxidant activity in terms of the ability to utilize the radicals of 2,2-diphenyl-1-picrylhydrazine (DPPH) and 2,2'-azino-bis(3-ethylbenzthiazolino-6-sulfonic acid) (ABTS) and in terms of iron-reducing ability (FRAP), the upper leaves, flowers, and fruits of meadowsweet can be considered plant raw materials suitable to obtain extracts with high antioxidant activity. Extracts of plant fruits and flowers also showed high antibacterial activity against the bacteria Bacillus subtilis and Pseudomonas aeruginosa.

The intensity of biofilm formation by heterotrophic bacteria isolated from soil ferrosphere

The intensity of biofilm formation by heterotrophic bacteria possessed ammonifying ability (Bacillus simplex ChNPU F1, Streptomyces canus NUChC F2, Streptomyces gardneri ChNPU F3), ammonifying and iron-reducing ability (Fictibacillus sp. ChNPU ZVB1) previously isolated from soil ferrosphere was studied. Methods used: indirect measurement of the biomass of the bacterial biofilm using the adsorption/desorption of crystal violet, the aggregation test (to determine aggregation properties), the salt aggregation test (to determine hydrophobicity). The correlation analysis between the intensity of biofilm formation and aggregation of strains showed a significant positive correlation. The studied strains of microorganisms did not show high adhesive properties, they were moderately-adhesive (B. simplex, S. canus and S. gardneri) and weakly-adhesive (Fictibacillus sp.). It is supposed that the role these bacteria in the microbial damage of materials is determined preferably by bioelectrochemical reactions (iron-reducing bacteria) and the production of corrosive and/or antimicrobial metabolites (ammonifying and iron-reducing bacteria), but not by the biofilms formation. The prospect of further research is to analyze the antagonistic properties and biofilm formation of heterotrophic bacteria under co-cultivation conditions, in particular, with sulfate-reducing bacteria.

Elucidation of Iron(III) Bioleaching Properties of Gram-Positive Bacteria.

Microbial-based iron reduction is an emerging technology used as an alternative to conventional chemical-based iron reduction. The iron reduction in kaolin refinement is vital for enhancing its commercial value. Extensive studies on microbial-based iron reduction mainly focus on Gram-negative bacteria, whereas little is understood about Gram-positive bacteria’s mechanism and potential application. This study aims to investigate the iron-reducing mechanism of two Gram-positive bacterial isolates, Bacillus cereus (B. cereus) and Staphylococcus aureus (S. aureus). By varying the growth environment of bacteria and monitoring the biochemical changes during the process of iron reduction, the results show that Gram-positive bacterial iron reduction performance depends on the medium composition, differing from Gram-negative bacteria-based reduction processes. Nitrogen-rich medium facilitates the microbial basification of the medium, where the alkaline conditions impact the microbial iron reduction process by altering the gene expression involved in intracellular pH homeostasis and microbial growth. This discovery will contribute to the mineral refining processes and promote the development of microbial-based bioprocesses for ore purification, while also laying the foundation for investigating other Gram-positive bacterial iron-reducing ability.

Reactivation of Passivated Biochar/Nanoscale Zero-Valent Iron by an Electroactive Microorganism for Cooperative Hexavalent Chromium Removal and Mechanisms

Nanoscale zero-valent iron (nZVI) shows excellent reduction of Cr(Ⅵ), but the passivation on its outer surface can restrict its longevity and performance. To tackle this problem, this work introduced Shewanella oneidensis MR-1, a dissimilatory iron-reducing bacterium, into the chemical reduction system of aged nZVI/biochar (B) and Cr(Ⅵ). The potential synergistic effect of Cr(Ⅵ) reduction of aged nZVI/B and MR-1 was systematically investigated under varying conditions. The results indicated that aged nZVI/B and MR-1 exhibited a synergistic effect at a pH of 7, and the removal rate of Cr(Ⅵ) increased by 51.3%. Further research showed that the synergistic effect could be attenuated with the increase in the initial Cr(Ⅵ) concentration and enhanced with the increase in the MR-1 concentration. The XPS spectra confirmed that Cr(Ⅵ) was mainly removed through reduction. The dissimilatory iron-reducing ability of MR-1 played a key role in enhancing the Cr(Ⅵ) reduction. The reductive dissolution of the oxidation layers not only released reactive sites inside the nZVI, but also reduced Cr(Ⅵ) by producing ferrous ions. Moreover, B promoted the reduction by dispersing the nZVI and mediating the extracellular electron transfer. This study provides a new insight into solving the passivation problem of the long-term application of nZVI for Cr(Ⅵ) removal, which is considered a promising solution for synergistically improving the performance of nZVI in environmental remediation.

Metronidazole does not show direct antioxidant activity in in vitro global systems

Metronidazole has been widely used topically and systemically for more than 50 years but data on its antioxidant properties are still incomplete, unclear and contradictory. Its antioxidant properties are primarily hypothesized based on in vivo results, therefore, studies have been performed to determine whether metronidazole has antioxidant activity in vitro. We used so-called global spectrophotometric and luminometric methods. Fe3+/Fe2+-reducing ability, hydrogen donor activity, hydroxyl radical scavenging property and lipid peroxidation inhibitory activity were investigated. Under the condition used, metronidazole has negligible iron-reducing ability and hydrogen donor activity. The hydroxyl radical scavenging capacity cannot be demonstrated. It acts as a pro-oxidant in the H2O2/.OH-microperoxidase-luminol system, but it can inhibit the induced lipid peroxidation. According to our results, metronidazole has not shown antioxidant activity in vitro but can affect redox homeostasis by a ROS-independent mechanism due to its non-direct antioxidant properties.

Screening technique on the selection of potent microorganisms for operation in microbial fuel cell for generation of power

This paper focuses on determination of the influence of electrochemically active mi­cro­or­ga­ni­sms on the transmission of electrons from the respiratory enzymes to the electrode and as­sembling of exoelectrogens to the simulated wastewater medium. In this study, the total of eight microorganisms were experimentally tested to exhibit growth and high iron-reducing ability in the absence of mediators. A major connection was observed between the growth and iron-reduction ability of the micro­organism. The growth and iron-reduction ability were monitored experimentally over time. Based on output data, the screening was done among eight different micro­organisms, where Escherichia coli -K-12 was chosen as the most potent micro­organism for its wide application in a microbial fuel cell (MFC). In the present study, various biochemical process factors were optimized statistically using Tagu­chi metho­dology for the rapid development of growth and iron-reducing assay conditions. The design of various experimental trials was carried out using five process factors at three levels with orthogonal arrays (OA) layout of L18. Five process factors, including quantity of lactose, volume of trace element solution, inoculum percentage, pH, and temperature, were taken into consideration as imperative process factors and optimized for evaluation of growth of bacteria and iron reduction ability. The larger-is-best signal to noise (S/N) ratio, together with analysis of variance ANOVA, were used during optimization. Anticipated results demonstrated that the enhanced bacterial growth of 124.50 % and iron reduction ability of 112.6 % can be achieved with 8 g/L of lactose, 2 ml of trace element solution, 4 % (v/v) of inoculum, pH 7, and temperature of 35 oC. Furthermore, the growth and iron reduc­tion time profiles of Escherichia coli-K12 were performed to determine its feasibility in MFC. Open circuit voltage of 0.555 V was obtained over batch study on a single chamber microbial fuel cell (SCMFC).

Antioxidant and iron-chelating properties of taxifolin and its condensation product with glyoxylic acid.

The condensation of taxifolin with glyoxylic acid was examined, and the properties of the resulting product were compared with those of taxifolin. The structure of the product was determined by NMR spectroscopy. The ability of the polyphenols to scavenge reactive oxygen species (ROS) was estimated by luminol-dependent chemiluminescence. The iron-chelating and iron-reducing activities were studied using absorption spectrophotometry. It was shown that the condensation leads to the formation of a dimer consisting of two taxifolin units linked through a carboxymethine bridge at the C-6 and C-8 positions of the A ring. The dimer exhibited a somewhat higher ROS scavenging activity than taxifolin. The iron-binding capacity of the compounds was proportional to the number of polyphenol units. The iron-reducing ability of the dimer was lower than that of taxifolin. Thus, the dimer possessed a higher antioxidant activity than the parent flavonoid. The data obtained may be useful for a better understanding of processes occurring in foods and beverages and in a search for new active compounds.

Bioreduction of iron compounds by Aeromonas hydrophila

The iron-reducing ability of a bacterial culture of Aeromonas hydrophila has been tested on two different ferric solid substrates: a natural mineral (containing goethite, FeO(OH), and hematite, Fe2O3), and a synthetic sodium jarosite (NaFe3(SO4)2(OH)6). Two fluid dynamic variables were investigated in the iron bioreduction process: pulp density and stirring speed. The maximum level of iron reduction was obtained with jarosite (87.8%) compared to 4% for the natural mineral. Similarly, cell numbers and bacterial growth kinetics were clearly different for both solid substrates. Unlike the natural ore, the number of microorganisms increased with increasing pulp density for jarosite. The effect of stirring on the iron bioreduction was more marked using the natural mineral than jarosite. The bioavailability of both iron sources was totally different. The results obtained suggest a different mechanism of bacterial attack: possibly direct for the synthetic jarosite and indirect for the natural mineral.

初始pH值对碱性和酸性水稻土微生物铁还原过程的影响

酸碱度（pH值）是水稻土铁还原过程的重要影响因素之一。通过模拟水稻土淹水厌氧培养，以Al₂（SO₄）₃和Na₂CO₃溶液分别调节碱性和酸性水稻土pH值至强酸性（pH值<5.0）、酸性（pH值5.0-6.5）、中性（pH值6.5-7.5）、碱性（pH值7.5-8.5）、强碱性（pH值 > 8.5），以此来研究5种初始pH值对水稻土泥浆铁还原过程的影响；通过微生物群落厌氧培养研究了2种水稻土菌悬液在6种pH值条件下的铁还原能力差异。结果表明，碱性水稻土铁还原潜势（<em>a</em>）、最大铁还原速率（<em>V</em>_max）随初始pH值的降低而下降，而达到最大铁还原速率所需的时间（<em>T_V</em>max）则延长。提高酸性水稻土初始pH值使铁还原<em>V</em>_max增加而<em>T_V</em>max缩短，但土壤中无定形氧化铁均能还原，初始pH值与<em>V</em>_max具有显著正相关关系。碱性和酸性水稻土的土壤菌悬液在试验pH值范围内厌氧培养，其铁还原能力在培养初期差异不显著，但培养后期的差异明显，且最终都能把培养液中氧化铁完全还原。随着初始pH值升高<em>T_V</em>max延长，<em>V</em>_max则降低，且均显著负相关，但碱性水稻土微生物群落的<em>V</em>_max在pH值6.00时最大。初始pH值和土壤类型对水稻土铁还原过程具有显著影响，且对土壤菌悬液微生物群的铁还原具有一定影响。;The pH value is one of the most important factors affecting iron reduction in paddy soils. The objective of this study was to determine how changes in initial pH affected iron reduction in paddy soils from Jilin (JL) and Jiangxi (JX) provinces. Anaerobic incubations were conducted using (1) soil slurries and (2) mixed microbial cultures that had been isolated from each soil type. The pH value of the alkaline JL samples was reduced with Al₂(SO₄)₃. The pH value of the acidic JX samples was increased using Na₂CO₃. The pH values of the soil slurries were strongly acidic (pH < 5.0), acidic (pH 5.0-6.5), neutral (pH 6.5-7.5), alkaline (pH 7.5-8.5), and strongly alkaline (pH > 8.5). The mixed microbial cultures were incubated in medium with pH ranging between 4.84-10.51. The Fe(Ⅱ) concentration and pH value of the samples were measured at regular intervals. A logistic model was used to analyze the characteristics of Fe(Ⅲ) reduction. The results showed that iron reduction potential and the maximum rate of iron reduction decreased as the initial pH value decreased. The time to reach the maximum rate of iron reduction increased as the initial pH value of the JL soil slurry declined. The maximum rate of iron reduction in the JL slurry decreased by nearly 50% as the pH value decreased, declining from (0.05±0.00) mg·g^-1·d^-1 at pH 10.51 to (0.02±0.00) mg·g^-1·d^-1 at pH 7.00. All amorphous iron oxides were reduced in the JX paddy soils, although the maximum rate of iron reduction increased and the time to reach the maximum rate of iron reduction decreased as the initial pH increased. The maximum rate of iron reduction in the JX soil was highest ((0.46±0.04) mg·g^-1·d^-1) and the time to reach the maximum rate of iron reduction was shortest ((3.65±0.21) d) at pH 8.19. There was a highly significant positive correlation between the maximum rate of iron reduction and the initial pH value of both soils (JL <em>r</em>=0.897, <em>P</em>=0.000; JX <em>r</em>=0.903, <em>P</em>=0.000). Mixed microbial cultures from both the JL and JX soil reduced all ferric iron, regardless of the initial pH value. It finally indicated that the iron reducing ability of microbial communities from both paddy soils were similar during the early stages of incubation but became different during the later stages. This observation provided support for the idea that facultative iron-reducing bacteria contribute to iron reduction in paddy soils. In the mixed cultures, the initial pH value increased. This was especially evident in the JX soil where the time to reach the maximum rate of iron reduction increased nearly six-fold, from (7.49±0.03) d at pH 4.84 to (45.2±0.3) d at pH 10.51. The maximum rate of iron reduction by the JL microbial community was negatively correlated with the initial pH value (<em>r</em>=-0.838, <em>P</em>=0.000). The maximum rate of iron reduction was highest at pH 6.00. The maximum rate of iron reduction by the JX microbial communities was highest at pH 4.84. There was a significantly negative correlation between the maximum rate of iron reduction and the initial pH value of the JX microbial community (<em>r</em>=-0.913, <em>P</em>=0.000). In conclusion, the effect of initial pH and soil type on iron reduction was significant in paddy soils. The initial pH has a certain influence on microbial communities and soil components.

Lack of Association between Nuclear Factor Erythroid-Derived 2-Like 2 Promoter Gene Polymorphisms and Oxidative Stress Biomarkers in Amyotrophic Lateral Sclerosis Patients

Oxidative stress involvement has been strongly hypothesized among the possible pathogenic mechanisms of motor neuron degeneration in amyotrophic lateral sclerosis (ALS). The intracellular redox balance is finely modulated by numerous complex mechanisms critical for cellular functions, among which the nuclear factor erythroid-derived 2-like 2 (NFE2L2/Nrf2) pathways. We genotyped, in a cohort of ALS patients (n = 145) and healthy controls (n = 168), three SNPs in Nrf2 gene promoter: −653 A/G, −651 G/A, and −617 C/A and evaluated, in a subset (n = 73) of patients, advanced oxidation protein products (AOPP), iron-reducing ability of plasma (FRAP), and plasma thiols (-SH) as oxidative damage peripheral biomarkers. Nrf2 polymorphisms were not different among patients and controls. Increased levels of AOPP (P < 0.05) and decreased levels of FRAP (P < 0.001) have been observed in ALS patients compared with controls, but no difference in -SH values was found. Furthermore, no association was found between biochemical markers of redox balance and Nrf2 polymorphisms. These data confirm an altered redox balance in ALS and indicate that, while being abnormally modified compared to controls, the oxidative stress biomarkers assessed in this study are independent from the −653 A/G, −651 G/A, and −617 C/A Nrf2 SNPs in ALS patients.

Oxidative stress and APO E polymorphisms in Alzheimer's disease and in mild cognitive impairment

A number of evidences indicates oxidative stress as a relevant pathogenic factor in Alzheimer's disease (AD) and mild cognitive impairment (MCI). Considering its recognized major genetic risk factors in AD, apolipoprotein (APO E) has been investigated in several experimental settings regarding its role in the process of reactive oxygen species (ROS) generation. The aim of this work has been to evaluate possible relationships between APO E genotype and plasma levels of selected oxidative stress markers in both AD and MCI patients.APO E genotypes were determined using restriction enzyme analysis. Plasma levels of oxidative markers, advanced oxidation protein products, iron-reducing ability of plasma and, in MCI, activity of superoxide dismutases were evaluated using spectrophotometric analysis.We found, compared to controls, increased levels of oxidized proteins and decreased values of plasma-reducing capacity in both AD patients (p < 0.0001) and MCI patients (p < 0.001); the difference between AD and MCI patients was significant only for plasma-reducing capacity (p < 0.0001), the former showing the lowest values. Superoxide dismutase activity was reduced, although not at statistical level, in MCI compared with that in controls. E4 allele was statistically associated (p < 0.05) with AD patients. When comparing different APO E genotype subgroups, no difference was present, as far as advanced oxidation protein products and iron-reducing ability of plasma levels were concerned, between E4 and non-E4 carriers, in both AD and MCI; on the contrary, E4 carriers MCI patients showed significantly decreased (p < 0.05) superoxide dismutase activity with respect to non-E4 carriers.This study, in confirming the occurrence of oxidative stress in AD and MCI patients, shows how it can be related, at least for superoxide dismutase activity in MCI, to APO E4 allele risk factor.

Bacterial Removal of Iron from Bauxite Ores: A Comparative Study Using Three Dissimilatory Iron Reducing Microorganisms

Bio-beneficiation of ores through iron removal is a common technique, but not yet tested for the case of bauxite. In this study we compared the iron reducing ability of three bacterial species with and without the chelating action of EDTA. Tests were carried out using a diasporic bauxite sample containing 19.3% Fe2Ο3 in the form of hematite, goethite and chamosite. Reductive dissolution was attempted using three neutrophilic, dissimilatory Fe(III) respirators, i.e. the facultative anaerobes Shewanella putrefaciens and Ferrimonas balearica and the strict anaerobe Desulfuromonas palmitatis. Almost 25% of Fe was reduced by D. palmitatis and S. putrefaciens and 30% by F. balearica in bauxite samples. In the case of S. putrefaciens and F. balearica, Fe(III) reduction took place without addition of EDTA, but most of the biologically produced Fe(II) reprecipitated. The addition of EDTA proved to hinder the bioreduction potential for both S. putrefaciens and F. balearica. On the contrary, D. palmitatis was able to reduce Fe(III) oxides only in the presence of EDTA. Moreover, the presence of EDTA helped maintain biogenic ferrous iron in solution.

Interaction of Iron with Polyphenolic Compounds: Application to Antioxidant Characterization

Antioxidant action of flavonoids and polyphenolics was analyzed in relation to iron coordination. Flavonoids including baicalein, baicalin, quercetin, and rutin showed little or no reducing activity, and enhanced the autooxidation of Fe2+ion. Ascorbate-mediated reduction of iron was rather inhibited by flavonoids. Nonflavonoid polyphenolics such as protocatechuic acid and chlorogenic acid, on the contrary, showed a potent iron-reducing ability, and protected Fe2+ion from autooxidation completely. Both flavonoids and nonflavonoids effectively inhibited the formation of thiobarbituric acid-reactive substances as a marker of lipid peroxidation of microsomes from rat liver. Flavonoids act as an antioxidant by inhibiting the oxygen radical formation through the enhanced oxidation of Fe2+ion as the prooxidant. Antioxidant properties of nonflavonoids can be explained by the formation of inactive Fe2+–polyphenol complex, which cannot react with oxygen, and/or can scavenge reactive oxygen species. Analysis of the action of polyphenolics on the iron redox state may be useful for characterization of the antioxidant effect.