Direct evolution of an alkaline fungal laccase to degrade tetracyclines.

A fungal laccase-mediator system capable of high effectively oxidizing tetracyclines under a wide pH range will benefit environmental protection. This study reported a directed evolution of a laccase PIE5 to improve its performance on tetracyclines oxidization at alkaline conditions. Two mutants, namely MutA (D229N/A244V) and MutB (N123A/D229N/A244V) were obtained. Although they shared a similar optimum pH and temperature as PIE5, the two mutants displayed approximately 2- and 5-fold higher specific activity toward the mediators ABTS and guaiacol at pHs 4.0 to 6.5, respectively. Simultaneously, their catalytic efficiency increased by 8.0- and 6.4-fold compared to PIE5. At a pH range of 5-8 and 28 °C, MutA or MutB at a final concentration of 2.5 U·mL-1 degraded 77 % and 81 % of 100 mg·L-1 tetracycline within 10 min, higher than PIE5 (45 %). Furthermore, 0.1 U·mL-1 MutA or MutB completely degraded 100 mg·L-1 chlortetracycline within 6 min in the presence of 0.1 mM ABTS. At pH 8.0, MutA degraded tetracycline and chlortetracycline following the routine pathways were reported previously based on LC-MS analysis.

Constructing myosin/high-density lipoprotein composite emulsions: Roles of pH on emulsification stability, rheological and structural properties.

The emulsification activity of myosin plays a significant role in affecting quality of emulsified meat products. High-density lipoprotein (HDL) possesses strong emulsification activity and stability due to its structural characteristics, suggesting potential for its utilization in developing functional emulsified meat products. In order to explore the effect of HDL addition on emulsification stability, rheological properties and structural features of myosin (MS) emulsions, HDL-MS emulsion was prepared by mixing soybean oil with isolated HDL and MS, with pH adjustments ranging from 3.0 to 11.0. The results found that emulsification activity and stability in two emulsion groups consistently improved as pH increased. Under identical pH, HDL-MS emulsion exhibited superior emulsification behavior as compared to MS emulsion. The HDL-MS emulsion under pH of 7.0-11.0 formed a viscoelastic protein layer at the interface, adsorbing more proteins and retarding oil droplet diffusion, leading to enhanced oxidative stability, compared to the MS emulsion. Raman spectroscopy analysis showed more flexible conformational changes in the HDL-MS emulsion. Microstructural observations corroborated these findings, showing a more uniform distribution of droplet sizes in the HDL-MS emulsion with smaller particle sizes. Overall, these determinations suggested that the addition of HDL enhanced the emulsification behavior of MS emulsions, and the composite emulsions demonstrated heightened responsiveness under alkaline conditions. This establishes a theoretical basis for the practical utilization of HDL in emulsified meat products.

Effect of epigallocatechin-3-gallate modification on the structure and emulsion stability of rice bran protein in the presence of soybean protein isolate.

For improving the emulsion stability of rice bran protein (RBP), RBP was modified by different concentrations of epigallocatechin-3-gallate (EGCG) in the presence of soybean protein isolate (SPI), and RBP-EGCG-SPI conjugate was prepared by alkaline pH-shifting. The results showed that the addition of EGCG led to an increase in the bound phenol content and the flexibility of the secondary structure, a decrease in the free sulfhydryl and disulfide bond content of the RBP-EGCG-SPI conjugate. EGCG covalently bound to RBP and SPI through non-disulfide bonds. When the concentration of EGCG was 10 % (w/v), the emulsifying activity index and emulsion stability index of conjugate reached the maximum value (36.61 m2/g and 255.61 min, respectively), and the conjugate had the best emulsion stability. However, an EGCG concentration above 10 % (w/v) negatively affected the emulsion stability, with increasing particle size due to protein aggregation. Summarily, the modification of EGCG improved the emulsion stability of conjugate by regulating the spatial structure of RBP-EGCG-SPI conjugate. The work provided an important guide to further improve the emulsion stability of RBP.

A Comparative Kidney Transcriptome Analysis of Bicarbonate-Loaded insrr-Null Mice.

The maintenance of plasma pH is critical for life in all organisms. The kidney plays a critical role in acid-base regulation in vertebrates by controlling the plasma concentration of bicarbonate. The receptor tyrosine kinase IRR (insulin receptor-related receptor) is expressed in renal ß-intercalated cells and is involved in alkali sensing due to its ability to autophosphorylate under alkalization of extracellular medium (pH > 7.9). In mice with a knockout of the insrr gene, which encodes for IRR, urinary bicarbonate secretion in response to alkali loading is impaired. The specific regulatory mechanisms in the kidney that are under the control of IRR remain unknown. To address this issue, we analyzed and compared the kidney transcriptomes of wild-type and insrr knockout mice under basal or bicarbonate-loaded conditions. Transcriptomic analyses revealed a differential regulation of a number of genes in the kidney. Using TaqMan real-time PCR, we confirmed different expressions of the slc26a4, rps7, slc5a2, aqp6, plcd1, gapdh, rny3, kcnk5, slc6a6 and atp6v1g3 genes in IRR knockout mice. Also, we found that the expression of the kcnk5 gene is increased in wild-type mice after bicarbonate loading but not in knockout mice. Gene set enrichment analysis between the IRR knockout and wild-type samples identified that insrr knockout causes alterations in expression of genes related mostly to the ATP metabolic and electron transport chain processes.

Integrated-Omics Study on the Transcriptomic and Metabolic Changes of Bacillus licheniformis, a Main Microorganism of Fermented Soybeans, According to Alkaline pH and Osmotic Stress.

Bacillus licheniformis has been widely utilized in the food industry as well as various agricultural industries. In particular, it is a main microorganism of fermented soybeans. In this study, the changes of the metabolome and transcriptome of B. licheniformis KACC15844, which had been isolated from fermented soybeans, were investigated depending on alkaline pH (BP) and a high salt concentration (BS) using an integrated-omics technology, focusing on leucine metabolism. Overall, carbohydrate (glycolysis, sugar transport, and overflow) and amino acid (proline, glycine betaine, and serine) metabolisms were strongly associated with BS, while fatty acid metabolism, malate utilization, and branched-chain amino acid-derived volatiles were closely related to BP, in both gene and metabolic expressions. In particular, in leucine metabolism, the formation of 3-methylbutanoic acid, which has strong cheesy odor notes, was markedly increased in BP compared to the other samples. This study provided information on how specific culture conditions can affect gene expressions and metabolite formations in B. licheniformis using an integrated-omics approach.

Quinolinium-Based Fluorescent Probes for Dynamic pH Monitoring in Aqueous Media at High pH Using Fluorescence Lifetime Imaging.

Spatiotemporal pH imaging using fluorescence lifetime imaging microscopy (FLIM) is an excellent technique for investigating dynamic (electro)chemical processes. However, probes that are responsive at high pH values are not available. Here, we describe the development and application of dedicated pH probes based on the 1-methyl-7-amino-quinolinium fluorophore. The high fluorescence lifetime and quantum yield, the high (photo)stability, and the inherent water solubility make the quinolinium fluorophore well suited for the development of FLIM probes. Due to the flexible fluorophore-spacer-receptor architecture, probe lifetimes are tunable in the pH range between 5.5 and 11. An additional fluorescence lifetime response, at tunable pH values between 11 and 13, is achieved by deprotonation of the aromatic amine at the quinolinium core. Probe lifetimes are hardly affected by temperature and the presence of most inorganic ions, thus making FLIM imaging highly reliable and convenient. At 0.1 mM probe concentrations, imaging at rates of 3 images per second, at a resolution of 4 µm, while measuring pH values up to 12 is achieved. This enables the pH imaging of dynamic electrochemical processes involving chemical reactions and mass transport.

Online Alkaline-pH Reverse Phase Nanoelectrospray-Tandem Mass Spectrometry Complements Conventional Low-pH Method for Global Proteomic Analysis.

The global proteome analysis was limited by the identification of peptides with low abundance or specific physiochemical properties. Here, a one-dimensional online alkaline-pH reverse phase nanoelectrospray-tandem mass spectrometry (alkaline-pH-MS/MS) method was developed and optimized for global proteomic analysis. In this method, peptides were separated on a nanoflow C18 column with an alkaline-pH mobile phase (pH = 8.0) and directly injected into the mass spectrometer. The unique peptides overlapped between alkaline-pH-MS/MS and conventional online low-pH reverse phase nanoelectrospray-tandem mass spectrometry (low-pH-MS/MS) were as low as 45%, strongly indicating that these two methods were complementary to each other. In addition, alkaline-pH-MS/MS showed identification capacity for a higher proportion of peptides with negative grand average of hydropathy (GRAVY) or high isoelectric point (pI). Compared to low-pH-MS/MS, alkaline-pH-MS/MS enabled enrichment preference toward histidine-, lysine-, methionine-, and proline-containing peptides. The complementarity of alkaline-pH-MS/MS and low-pH-MS/MS was further demonstrated for the analysis of tryptic digests from 15 intrahepatic cholangiocarcinoma (iCCA) cell lines. The alternating 60 min alkaline-pH-MS/MS plus 60 min low-pH-MS/MS method outperformed the conventional 120 min low-pH-MS/MS method in both the identification of amino acid variants and protein groups. Therefore, we established the alkaline-pH-MS/MS method as a simple, competitive, alternative method to low-pH-MS/MS for global proteomic analysis.

Turn-On Fluorescent pH Probes for Monitoring Alkaline pHs Using Bis[2-(2'-hydroxyphenyl)benzazole] Derivatives.

For surveilling human health, industries, and the environment, pH monitoring is important. Numerous studies on fluorescent probes have been conducted to monitor various pH ranges. However, fluorescent probes that are capable of sensing alkaline regions are rare. In this study, we propose turn-on-type fluorescent probes for detecting alkaline pHs using bis[2-(2'-hydroxyphenyl)benzazole] (bis(HBX)) derivatives. These probes have high pKa values (from 9.7 to 10.8) and exhibit strong fluorescence intensity and color changes at alkaline pHs. Probes derived from bis(HBX) exhibit good photostability, reversibility, and anti-interference toward pH variations, which can be identified as a certain fluorescence change toward a basic pH. Therefore, compounds would be advantageous to use fluorescent probes for monitoring alkaline pH changes.

Understanding the (dis)-assembly of in situ forming hydrogel coatings in a 2D model system.

HYPOTHESIS: Injectable hydrogels are important in situ forming implants for tissue regeneration at damaged sites. Understanding the behavior of these systems in a complex in vivo environment remains a challenge. Ultrathin films as 2D model systems are expected to provide fundamental insights into formation and (bio)degradation at material-liquid interfaces, and are also applicable as bioresponsive coatings. EXPERIMENTS: Hydrogel ultrathin films are prepared by covalently cross-linking four-arm PEG macromers with maleimide end-groups (PEG4MAL) at alkaline pH using two different types of dithiol-bearing cross-linkers - thio-depsipeptide (TDP) or 3,6-Dioxa-1,8-octanedithiol (DODT). This thiol-Michael addition "click" reaction is carried out at the air-water interface using the Langmuir technique. Morphological observation in real time is carried out by Brewster angle microscopy (BAM) and in coatings using atomic force microscopy (AFM). Stability against enzymatic and oxidative degradation is evaluated in the same setup. FINDINGS: Non-cross-linked PEG or PEG incubated with cross-linkers at slightly acidic pH desorbs from the interface over time. Cross-linking of PEG at alkaline pH renders 2D hydrogel networks (thickness <1 nm) that are stable against desorption. They are easily transferrable onto solid mica surfaces, forming homogenous coatings as revealed by AFM. The type of dithiol cross-linker used to form the branching centers influences the degradability of these 2D hydrogel networks in the presence of lipase, peroxides, or bases. For example, enzymatic degradation of the 2D hydrogel networks can be switched "on" or "off" depending on the cleavable sites in the cross-linkers.

Adaptive growth and acidogenic fermentation performance of haloalkaliphilic bacterial communities enriched from biofilms colonising strongly alkaline and saline bauxite residue.

The present study aimed to characterise the adaptive growth and acidogenic fermentation performance of haloalkaliphilic bacteria sourced from field biofilms colonising seawater-treated bauxite residue, under moderate and extremely alkaline pH conditions (8.5 to 10.8) and coupled saline (EC ≈ 50 mS/cm) conditions. The haloalkaliphilic bacterial communities demonstrated strong adaptiveness to the increasing pH from 8.5 to 10.8. The dominant groups were Exiguobacterales and Bacillales at pH 8.5 and 10, but Lactobacillales and Bacillales at pH 10.8. The exposure to pH 10.8 initially delayed bacterial growth in the first 24 h, but which rapidly recovered to a peak rate at 48 h similar to that in the pH 10 treatment. Correspondingly, lactic acid concentration at pH 10.8 rapidly rose to as high as >2000 mg/L at 48 h. Bacterial growth and organic acid production were positively related to carbohydrate supply. Overall, these bacterial groups fermented glucose to produce mainly lactic acid (>80 %) and other acids (such as acetic acid, formic acid, and succinic acid), leading to 0.5-2.0 units of pH reduction, despite the strong buffering capacity in the culture solution. The bacteria could up-regulate their phosphatase activity to mineralise the organic P in the basal nutrient broth, but increasing soluble phosphate-P at a 1:10 of glucose-C was beneficial. The biofilm-sourced bacteria communities contained redundant fermentative haloalkaliphilic groups which were adaptive to strongly alkaline pH and saline conditions.

pH and microbial community determine the denitrifying activity in the presence of nitrate-containing radioactive waste.

An important fraction of the currently stored volume of long-lived intermediate-level radioactive waste in Belgium contains large amounts of NaNO3 homogeneously dispersed in a hard bituminous matrix. Geological disposal of this waste form in a water-saturated sedimentary formation such as Boom Clay will result in the leaching of high concentrations of NaNO3, which could cause a geochemical perturbation of the surrounding clay, possibly affecting some of the favorable characteristics of the host formation. In addition, hyper-alkaline conditions are expected for thousands of years, imposed by the cementitious materials used as backfill material. Microbial nitrate reduction is a well-known process and can result in the accumulation of nitrite or nitrogenous gases. This could lead to the oxidation of redox-active Boom Clay components, which could (locally) decrease the reducing capacity of the clay formation. Here, we compared nitrate reduction processes between two microbial communities at different pH related to a geological repository environment and in the presence of a nitrate-containing waste simulate during 1 year in batch experiments. We showed that the microbial community from in Boom Clay borehole water was able to carry out nitrate reduction in the presence of acetate at pH 10.5, although the maximum rate of 1.3 ± 0.2 mM NO3 -/day was much lower compared to that observed at pH 9 (2.9 mM NO3 -/day). However, microbial activity at pH 10.5 was likely limited by a phosphate shortage. This study further confirmed that the Harpur Hill sediment harbors a microbial community adapted to high pH conditions. It reduced twice as much nitrate at pH 10.5 compared to pH 9 and the maximum nitrate reduction rate was higher at pH 10.5 compared to that at pH 9, i.e., 3.4 ± 0.8 mM NO3 -/day versus 2.2 ± 0.4 mM NO3 -/day. Both communities were able to form biofilms on non-radioactive Eurobitum. However, for both microbial communities, pH 12.5 seems to be a limiting condition for microbial activity as no nitrate reduction nor biofilm was observed. Nevertheless, pH alone is not sufficient to eliminate microbial presence, but it can induce a significant shift in the microbial community composition and reduce its nitrate reducing activity. Furthermore, at the interface between the cementitious disposal gallery and the clay host rock, the pH will not be sufficiently high to inhibit microbial nitrate reduction.

Insulin Receptor-Related Receptor Regulates the Rate of Early Development in Xenopus laevis.

The orphan insulin receptor-related receptor (IRR) encoded by insrr gene is the third member of the insulin receptor family, also including the insulin receptor (IR) and the insulin-like growth factor receptor (IGF-1R). IRR is the extracellular alkaline medium sensor. In mice, insrr is expressed only in small populations of cells in specific tissues, which contain extracorporeal liquids of extreme pH. In particular, IRR regulates the metabolic bicarbonate excess in the kidney. In contrast, the role of IRR during Xenopus laevis embryogenesis is unknown, although insrr is highly expressed in frog embryos. Here, we examined the insrr function during the Xenopus laevis early development by the morpholino-induced knockdown. We demonstrated that insrr downregulation leads to development retardation, which can be restored by the incubation of embryos in an alkaline medium. Using bulk RNA-seq of embryos at the middle neurula stage, we showed that insrr downregulation elicited a general shift of expression towards genes specifically expressed before and at the onset of gastrulation. At the same time, alkali treatment partially restored the expression of the neurula-specific genes. Thus, our results demonstrate the critical role of insrr in the regulation of the early development rate in Xenopus laevis.

Human growth hormone inclusion bodies present native-like secondary and tertiary structures which can be preserved by mild solubilization for refolding.

BACKGROUND: Native-like secondary structures and biological activity have been described for proteins in inclusion bodies (IBs). Tertiary structure analysis, however, is hampered due to the necessity of mild solubilization conditions. Denaturing reagents used for IBs solubilization generally lead to the loss of these structures and to consequent reaggregation due to intermolecular interactions among exposed hydrophobic domains after removal of the solubilization reagent. The use of mild, non-denaturing solubilization processes that maintain existing structures could allow tertiary structure analysis and increase the efficiency of refolding. RESULTS: In this study we use a variety of biophysical methods to analyze protein structure in human growth hormone IBs (hGH-IBs). hGH-IBs present native-like secondary and tertiary structures, as shown by far and near-UV CD analysis. hGH-IBs present similar λmax intrinsic Trp fluorescence to the native protein (334 nm), indicative of a native-like tertiary structure. Similar fluorescence behavior was also obtained for hGH solubilized from IBs and native hGH at pH 10.0 and 2.5 kbar and after decompression. hGH-IBs expressed in E. coli were extracted to high yield and purity (95%) and solubilized using non-denaturing conditions [2.4 kbar, 0.25 M arginine (pH 10), 10 mM DTT]. After decompression, the protein was incubated at pH 7.4 in the presence of the glutathione-oxidized glutathione (GSH-GSSG) pair which led to intramolecular disulfide bond formation and refolded hGH (81% yield). CONCLUSIONS: We have shown that hGH-IBs present native-like secondary and tertiary structures and that non-denaturing methods that aim to preserve them can lead to high yields of refolded protein. It is likely that the refolding process described can be extended to different proteins and may be particularly useful to reduce the pH required for alkaline solubilization.

Enterococcus faecalis V583 cell membrane protein expression to alkaline stress.

Enterococcus faecalis is able to adapt to alkaline conditions and is commonly recovered from teeth in which endodontic treatment has failed. The role that E. faecalis membrane proteins play in survival strategies to extreme alkaline conditions is unclear. We grew E. faecalis V583 in a chemostat at pH 8 and 11 at one-tenth the organism's relative maximum growth rate. Following membrane shaving, isotope-coding protein labels were added at the peptide level to samples and then combined. The relative proportion of membrane proteins were identified using LC-ESI mass spectrometry and MaxQuant analysis. Ratios of membrane proteins were log2 transformed, with proteins deviating by more than 1 SD of the mean considered to be up- or down-regulated. A total of six proteins were up-regulated in pH 11 including: EF0669 (polysaccharide biosynthesis family); EF1927 (glycerol uptake facilitator), and EF0114 (glycosyl hydrolase). A total of five proteins were down-regulated including: EF0108 (C4-dicarboxylate transporter); EF1838 (PTS system IIC component); EF0456 (PTS system IID component); and EF0022 (PTS mannose-specific IID component). In extreme alkaline conditions, the membrane proteins of E. faecalis seem to be involved in a shift of carbohydrate metabolism from the PTS system to glycerol, which supports the formation of a protective capsule protecting the cell.

Long-term alkaline volatile fatty acids production from waste streams: Impact of pH and dominance of Dysgonomonadaceae.

Alkaline co-fermentation of primary sludge and external organic waste (OW) was studied to elucidate the influence of substrate ratios and long-term system robustness and microbial community dynamics using batch and semi-continuous reactors. Volatile fatty acid (VFA) production increased with increasing OW fraction in the substrate due to synergistic effects of co-degradation. VFA production at pH 10 increased up to 30,300 mgCOD/L (yield of 630 mg COD/gVSfed) but reduced over time to ≈10,000 mgCOD/L. Lowering pH to 9 led to the restoration of VFA production with a maximum of 32,000 mg COD/L (676 mg COD/g VSfed) due to changes in microbial structure. VFA was composed mainly of acetic acid, but propionic acid increased at pH 9. The microbial community was dominated by Bacillaceae (34 ± 10%) and Proteinivoracales_uncultured (16 ± 11%) at pH 10, while Dysgonomonadaceae (52 ± 8%) was enriched at pH 9. The study demonstrated a zero-waste strategy that turns organic wastes into bio-based products.

Alkaline pH in intracranial tuberculomas: A 31Phosphorus magnetic resonance spectroscopy study.

Objectives: Intracranial tuberculomas are one of the common causes of space-occupying lesions of the brain in developing countries. Proton (1H) magnetic resonance spectroscopy (MRS) has shown lipid peak in intracranial tuberculomas as a characteristic feature. Phosphorus (31P) MRS has been used to evaluate intracranial lesions and to calculate tissue pH non-invasively. The aim of this study is to evaluate intracranial tuberculomas using 31PMRS. Materials and Methods: Intracranial tuberculomas proven by stereotactic or surgical biopsy were included in the study. After routine T1- and T2-weighted sequences, 31P MRS was performed using single-voxel intravoxel in vivo spectroscopy (ISIS) technique in the central core of the tuberculoma (voxel size 1-2 mm3). The pH was estimated using Petroff 's method using the chemical shift between phosphocreatine and Pi. Results: 31P MRS was available for 26 patients, in which there was significant positive correlation between high-energy phosphate metabolites, (markers of bioenergetic status), and low-energy phosphate metabolites (membrane phospholipids and inorganic phosphate). The calculated pH was slightly alkaline and varied from 6.97 to 7.22. Conclusion: Intracranial tuberculomas showed alkaline pH in 31P MRS and this may be useful in the characterization of these lesions and possibly also in their treatment.

Correlation between chemical composition and 90Sr concentrations in groundwater of the Chornobyl NPP industrial site.

The volumetric activity of the divalent 90Sr ion in groundwater at the Chornobyl NPP industrial site ranges from 1 to 2 to 400-3800 Bq/l. The increase in groundwater radionuclides concentrations is associated with the reduced sorption properties of local sediments, which affect the migration capacity of radionuclides in the environment. The decrease of the 90Sr sorption properties of sediments is caused by changes in the chemical composition of groundwater. A new statistical method has been performed. Method based on the Monte Carlo method in order to evaluate the correlations between the 90Sr volumetric activity and the groundwater chemical composition components. Simulation results using this method suggest a correlation between the volumetric activity of 90Sr, the concentrations cations, the pH, and the oxidation index (organic contents). A direct correlation was established between the volumetric activity of 90Sr, Ca2+ concentrations and the pH of groundwater in the range from 7 to 12.4. It was revealed that the concentrations of Na+ and K+ do not affect the conditions of 90Sr migration with groundwater. There is an inverse correlation between the concentration of 90Sr and the oxidation index, which is an indirect indicator of the organic substances content in water. Thus, the presence of organic substances in the groundwater effectively promotes sorption of 90Sr. The proposed method of geochemical statistics enables a quantitative assessment of groundwater monitoring results.

Growth and photosynthesis acclimated response of the cyanobacterium Fischerella sp. FS 18 exposed to extreme conditions: alkaline pH, limited irradiance, and carbon dioxide concentration.

The true-branching heterocystous cyanobacterium Fischerella sp. FS 18 is widely distributed in paddy fields (North) and petroleum polluted soils (South) in Iran. This investigation tested the hypothesis that the cyanobacterium can acclimatize under the combined effect of extreme environmental conditions. Here, we analysed the physiological response of the cyanobacterium under extremely limited irradiance (2 µmol photon m-2 s-1); limited carbon dioxide concentration (no aeration) at alkaline pHs (9 and 11) for up to 96 h. When the cyanobacterium was exposed to these extreme conditions at pH 11, we observed a decline in growth, oxygen liberation, photosystems ratio, chlorophyll a, and phycobilisomes activity compared to pH 9 after 24 h. Besides, we registered a significant decrease in maximum photochemical efficiency and activity of photosystem II at pH 11. The comparative single-cell study revealed that pH 9 caused higher efficiency of photosystem II and I, while increasing alkalinity pH 11 led to disturbed phycobilisomes activity after 24 h. This strain was able to recover its structures after 96 h. In addition, spectroscopy analyses revealed the presence of the Mycosporine-like amino acid at pH 9.

Heavy metal- and organic-matter pollution due to self-heating coal-waste dumps in the Upper Silesian Coal Basin (Poland).

This study provides potential insight between self-heating coal-waste dumps and related environmental pollution in southern Poland. Samples collected from dumps in the Upper Silesian Coal Basin were used to quantify released contents of organic- and inorganic pollutants, i.e., polycyclic aromatic hydrocarbons (PAHs) and trace elements (Pb, Cd, Cr, Cu, Zn, Ni, Hg, As). Elevated Hg concentrations (~100-1078 mg/kg) and Pb (~600-2000 mg/kg) attest to the evaporation of these metals from deeper parts of the dumps. The acidic pH levels (3.0-4.5) may help to mobilize these elements. Pearson's correlation coefficients for samples analyzed by AAS and ICP-MS indicate a similar origin for Cd, Zn, and As. Mostly 2- and 3-ring PAHs, especially anthracene in burnt soil, dominate in the samples. Chlorinated PAHs, thiophenol, pyridines, quinolines (and derivatives) in thermally-altered samples, and waste containing pyrolytic bitumen indicate coking conditions. The high levels of Hg, Pb, and Cd, and chlorinated PAHs and nitrogen heterocycles formed or enriched during self-heating in these dumps should be deemed a significant environmental hazard. Calculating the lifetime cancer risks due to PAHs and heavy metals accumulations in the dumps are substantial, and access to these dumps should be prohibited.

Acidophilic Iron- and Sulfur-Oxidizing Bacteria, Acidithiobacillus ferrooxidans, Drives Alkaline pH Neutralization and Mineral Weathering in Fe Ore Tailings.

The neutralization of strongly alkaline pH conditions and acceleration of mineral weathering in alkaline Fe ore tailings have been identified as key prerequisites for eco-engineering tailings-soil formation for sustainable mine site rehabilitation. Acidithiobacillus ferrooxidans has great potential in neutralizing alkaline pH and accelerating primary mineral weathering in the tailings but little information is available. This study aimed to investigate the colonization of A. ferrooxidans in alkaline Fe ore tailings and its role in elemental sulfur (S0) oxidation, tailings neutralization, and Fe-bearing mineral weathering through a microcosm experiment. The effects of biological S0 oxidation on the weathering of alkaline Fe ore tailings were examined via various microspectroscopic analyses. It is found that (1) the A. ferrooxidans inoculum combined with the S0 amendment rapidly neutralized the alkaline Fe ore tailings; (2) A. ferrooxidans activities induced Fe-bearing primary mineral (e.g., biotite) weathering and secondary mineral (e.g., ferrihydrite and jarosite) formation; and (3) the association between bacterial cells and tailings minerals were likely facilitated by extracellular polymeric substances (EPS). The behavior and biogeochemical functionality of A. ferrooxidans in the tailings provide a fundamental basis for developing microbial-based technologies toward eco-engineering soil formation in Fe ore tailings.