Bacterial Oxidation Research Articles

Probing the mechanism of the dedicated NO sensor [4Fe-4S] NsrR: the effect of cluster ligand environment

NsrR from Streptomyces coelicolor is a bacterial nitric oxide (NO) sensor/nitrosative stress regulator as its primary function, and has been shown to have differential response at low, mid, and high levels of NO. These must correspond to discrete structural changes at the protein-bound [4Fe-4S] cluster in response to stepwise nitrosylation of the cluster. We have investigated the effect of the monohapto carboxylate ligand in the site differentiated [4Fe-4S] cluster cofactor of the protein NsrR on modulating its reactivity to NO with a focus on indentifying mechanistic intermediates. We have prepared a synthetic model [4Fe-4S] cluster complex with tripodal ligand and one single site differentiated site occupied by either thiolate or carboxylate ligand. We report here the mechanistic details of sequential steps of nitrosylation as observed by ESI MS and IR spectroscopy. Parallel non-denaturing mass spectrometry analyses were performed using site-differentiated variants of NsrR with the native aspartic acid, cysteine, or alanine in the position of the forth ligand to the cluster. A mono-nitrosylated synthetic [4Fe-4S] cluster was observed for the first time in a biologically-relevant thiolate-based coordination environment. Combined synthetic and protein data give unprecedented clarity in the modulation of nitrosylation of a [4Fe-4S] cluster.

Methane emissions from subglacial meltwater of three alpine glaciers in Yukon, Canada

ABSTRACT Subglacial meltwater of land-terminating glaciers in Greenland and Iceland are sources of methane (CH4) to the atmosphere, but sparse empirical data exist about the spatial distribution of subglacial CH4 production and emission from glaciers in other regions of the world. This study presents the first measurements of CH4 emissions from the subglacial meltwater of three outlet glaciers of the St. Elias Mountains in Yukon, Canada. Dissolved CH4 concentrations were highly elevated at 45, 135, and 250 times compared to the atmospheric equilibrium concentration in the meltwater of Dusty, Kluane, and Donjek glaciers, respectively. Dissolved CO2 concentrations were depleted relative to the atmospheric equilibrium. This points to the meltwater being a source of CH4 and a sink of CO2. Stable carbon (13C) and hydrogen (2H) isotopic signatures of the subglacial CH4 were depleted compared to atmospheric CH4 at all sites, indicating both biotic and abiotic sources and possible alteration from bacterial CH4 oxidation in the meltwater. No relation was found between CH4 concentrations in the meltwater and the meltwater chemistry or the size of the glaciers in this study. These findings suggest that CH4 emissions from subglacial environments under alpine glaciers may be a more common phenomenon than previously thought.

Occurrence and Sources of Polycyclic Aromatic Hydrocarbons and Factors Influencing Their Accumulation in Surface Sediment of a Deep-Sea Depression, Namely, the Tatar Trough (Tatar Strait, the Sea of Japan)

The concentrations of 14 polycyclic aromatic hydrocarbons (PAHs) in the sediment of the Tatar Trough were studied. Despite the increase in PAH concentrations over recent decades, which is likely the result of the handling and transportation of fossil fuels, PAH levels and ecological risk were found to be low. The spatial pattern revealed that higher PAH concentrations were mainly in the deeper water sites, suggesting that trough slope failure transported the PAHs to the deeper part of the basin. There was no correlation between the PAHs and grain size or the PAHs and organic carbon that is related to the PAH input from a variety of sources and the heterogeneity of organic matter. The PAH composition, isomer ratio, and PCA identified two areas with different PAH sources. The most northern part of the Tatar Trough received petrogenic PAHs that are probably transported downslope from the northern Tatar Strait where fossil fuels are handled in some ports. Another trough part was polluted by the PAHs from the combustion of coal and biomass and the exhaust of marine vehicles. The minor presence of genes responsible for aerobic PAH destruction can be explained by the anaerobic degradation of PAHs or the spontaneous creation of favorable conditions that promote bacterial PAH oxidation.

Combined Bacterial and Pressure Oxidation for Processing High-Sulfur Refractory Gold Concentrate

Microbially assisted bio-oxidation of sulfide concentrates in stirred-tank reactors (stirred-tank reactor bio-oxidation (STRB)) and acid pressure oxidation (POX) are widely used to pretreat refractory sulfide concentrates and increase gold extraction via cyanidation. Continuous STRB requires a comparatively long residence time; however, in some cases, it cannot effectively oxidize some sulfide minerals. POX enables oxidation in a short residence time. At the same time, if a processed concentrate contains a large amount of sulfur, it decreases the ratio of the solid mineral phase to liquid (pulp density) during POX and limits its economic attractiveness. In the present work, experiments were performed to investigate the problems associated with both processing methods for refractory sulfide concentrates. The experiments combined both treatments (STRB and POX) based on the example of a pyrite–arsenopyrite gold-bearing concentrate. The gold recovery from the untreated concentrate via cyanidation reached 58%. Continuous STRB for 2, 4, and 6 days oxidized 43, 74, and 79% of the sulfide sulfur (Ss), respectively. The gold recovery rates from the bio-oxidation residues were 68, 82, and 88%, respectively. The pressure oxidation of both the concentrate and STRB residues increased Ss oxidation by 97–99% and gold recovery by 96–97%. For 2 days, STRB decreased the Ss content and increased the possible liquid-to-solid ratio for POX. The combined processes result in a new promising direction because the POX stage allows high gold recovery, whereas combining STRB and POX provides products for further POX in terms of Ss content and increases POX productivity.

Antimicrobial activity of in-situ bacterial nanocellulose-zinc oxide composites for food packaging

Active substances such as zinc oxide nanoparticles (ZnO) have been extensively explored due to their antimicrobial properties, low cost and scalability. Yet, their effectiveness is highly dependent on their morphology and specific surface area. Bacterial nanocellulose (BNC) is a suitable carrier due to its ability to transport and deliver active substances. In the case of nanocellulose-ZnO composites, conclusions drawn from antimicrobial studies are often based on only a few representatives of Gram-positive and Gram-negative bacteria. A more comprehensive study using different species and strains, and different methods to assess antimicrobial activity is required. Therefore, in this work, the antimicrobial activity of ZnO suspensions and BNCZnO films was assessed against a wide range of Gram-negative and Gram-positive bacteria using disc diffusion and viable cell count assays. Regarding the results of the disc diffusion assay, the increase of ZnO content (21–27% mZn/mBNCZnO) (in both ZnO suspensions and BNCZnO films), increased antimicrobial activity against all Gram-negative bacteria tested and some Gram-positive bacteria. In the viable cell count assay, BNCZnO films were effective against Escherichia coli (3 log reduction) and Listeria monocytogenes (1–3 log reduction) after 24 h. Low temperatures reduced the antimicrobial activity of BNCZnO.

Control of the temperature regime of the process of bacterial oxidation on the basis of fuzzy logic

The work is devoted to modeling the temperature control system for the process of bacterial oxidation of refractory gold-bearing sulfide ores. The simulation was performed using the Fuzzy Logic Toolbox editor in the MATLAB software package. The substantiation of the set of input and output variables, the type of membership functions was carried out, the base of rules for the inference engine was formed. The main stages of modeling are described and the results are analyzed. The use of trapezoidal membership functions is substantiated.

Kinetics study comparing bacterial growth and iron oxidation kinetics over a range of temperatures 5–45 °C

This comprehensive study summarizes kinetic data from experiments performed over a wide temperature range that overlaps the physiological operating temperature windows for most mesophilic Fe-oxidizers. Three acidophilic autotrophic bacterial strains Acidithiobacillus (At.) ferrivorans, At. ferrooxidans and Leptospirillum (L.) ferriphilum were investigated in this work in order to compare their growth and iron oxidation kinetics over a temperature range of 5–45 °C. On-line gas analysis was applied to determine the O2 and CO2 consumption rates during the culture incubation. Despite the genotypic differences these three strains share many common physiological traits. At t = 30 °C, the specific growth rate (μ) at all three species reached 0.11 h−1 which is equivalent to generation time 6.5 h. Maximum ferrous‑iron oxidation rate per unit of biomass was achieved with L. ferriphilum at t = 40 °C and approached 10 mmol Fe2+ (C-mmol) h−1. The temperature of incubation had a profound effect on the specific rates, while the kinetic parameter Ks/Ki at the Acidithiobacilli strains remained unaffected. Cultures with Leptospirillum incubated at temperatures >35 °C were capable of iron oxidation at redox potentials close to +950 mV and kept constant specific rates until Fe2+ depletion. The parameter Ks/Ki at L. ferriphilum was two order of magnitude lower than for the Acidithiobacilli. However, this feature disappears at temperatures below 30 °C, where Ks/Ki has a value comparable to Acidithiobacilli, which suggests that L. ferriphillum uses different Fe oxidation systems depending on temperature conditions. Strong correlation was observed between ferrous iron oxidation, and carbon dioxide fixation in the exponentially growing cultures with the yield coefficient (YSX) approaching 14 μmol C fixed per mmol Fe2+ oxidized. The kinetic parameters differed significantly between bacterial strains under “extreme” temperatures (t < 10 °C; t > 35 °C). All three bacterial strains were capable of oxidizing iron over the entire range (5–45 °C) of incubation temperatures. Neither At. ferrivorans nor At. ferrooxidans showed exponential growth at the temperature 40 °C. Bacterial iron oxidation not associated with growth was observed during incubation at 5 °C. At. ferrivorans, was the only species that can grow exponentially at a temperature of 5 °C. Moreover, it differed from the other species by greater sensitivity to low pH which seems to be more pronounced at temperatures t < 10 °C, with minimum of pH 1.9 for growth.

Flue gas Pb0 removal from sludge incineration through biological lead oxidation coupled denitrification

Lead (Pb0) in flue gas from sludge incineration can seriously harm human health especially lead poisoning and blood lead increase. Microbial lead (Pb0) oxidation associated with nitrate reduction might be poorly understood in eliminating Pb0 pollution in flue gas from sludge incineration. In this study, a denitrifying bioreactor (DBR) was investigated for Pb0 removal from flue gas. Pb0 removal efficiency achieved 87% in 60-day operation. Dominated Pb0-oxidating-denitrifying bacteria such as Azoarcus, Thauera and Stappia could realize bacterial Pb0 oxidation and nitrate reduction through the regulation of lead oxidation genes (katE, K07217, aoxA, aoxB, moxA) and denitrification gene (napAB and narHGI). The up-regulation of amino acids and polysaccharide biosynthesis, transporters and phosphatase-relevant genes provided evidence of their involvement in the transformation of lead. The bio-oxidation of Pb0 adsorbed on EPS was coupled with denitrification, where Pb0 and nitrate served as the electron donor and terminal electron acceptor, respectively, and thereby formed redox between Pb0 and nitrate. Pb2+ oxidized from Pb0 was intracellularly accumulated, and complexed with EPS by binding with –OH and P = O. Pb0-containing flue gas was bio-stabilized in the form of Pb5(PO4)3Cl and protein/polysaccharide-Pb2+. Pb0 in flue gas was adsorbed by denitrifying bacteria, oxidized to Pb2+ coupling with denitrification, and biostabilized to achieve the removal of Pb0 from flue gas. These results show that the DBR advanced treatmenttechnology is achievable and provide new possibilities for applying the denitrifying bioreactor to remove heavy metals from flue gas.

Biotransformation of coal fly ash with high carbon content; behavior and release patterns of coal fly ash constituents under the influence of allochtonic Pseudomonas stutzer MT1

The aim of this study was to analyze the influence of Pseudomonas stutzeri MT1 on the weathering of CFA, with particular emphasis on the transformation of unburnt carbon. Batch experiment with two common types of coal fly ash (one with high carbon content) showed that microbial transformation leads to metal (loid)s and organic compounds release. The concentrations of metal (loid)s leached from CFA were the highest for As and Al, reaching 951 μg/L and 1353 μg/L respectively, in the presence of bacteria. It was shown that some metal (loid)s (Al, Fe, Cr, As) leached in higher quantities when bacteria used CFA as a sole carbon source as compared to variants where external carbon source was provided. Anthracene or phenanthrene were present in every leachate variant. The addition of bacteria resulted in a higher presence of short-chain carboxylic acids as well as 9,10-anthracenedione, which is assumed to be a product of the bacterial oxidation of anthracene. Based on the performed experiments we noticed that the microbial consumption of carbon contained within CFA was crucial to increasing the leaching rate of metal (loid)s, which may have consequences for the long-term storage of CFA.

Study of the Mechanism of Dearsenification of Arsenopyrite Enhanced by Mechanically Modified Pyrite and Bacteria

This study investigated the impact of mechanically modified pyrite on the dearsenification of arsenopyrite through bacterial oxidation. Pyrite was mechanically modified using a planetary high-energy ball mill, and the resulting changes in the crystal structure were characterized using particle size analysis, specific surface area measurements, scanning electron microscopy (SEM), Raman spectroscopy, and X-ray diffraction (XRD). Pearson correlation analysis was employed to examine the relationship between the crystal structure of modified pyrite and the bacterial oxidation of arsenopyrite. The study also investigated the mechanism of arsenic removal using pyrite with varying degrees of mechanical modification during arsenopyrite bio-oxidation. The key findings are as follows: (1) The maximum extent of arsenopyrite dearsenification by bacteria was achieved at a pyrite modification degree of 400 r·min−1 and reached 96.01%, which was 14.49% higher than that for unmodified pyrite and 24.13% higher than that in the absence of pyrite. At this degree, the modified pyrite exhibited a median diameter of 1.33 μm (minimum) and a specific surface area of 3123 m2·kg−1 (maximum). (2) Pearson correlation analysis revealed a significant negative correlation between the extent of arsenopyrite dearsenification and the particle size and grain size of pyrite, and a significant positive correlation with the specific surface area and the amorphous degree of pyrite. A smaller particle size and grain size, larger specific surface area, and a higher amorphous degree were associated with a higher extent of dearsenification. (3) The mechanism of enhanced arsenopyrite dearsenification using mechanically modified pyrite was attributed to autocatalytic dissolution. The galvanic effect directly enhanced dearsenification, while the mechanical modification facilitated the direct oxidation of pyrite by bacteria, releasing a significant amount of Fe3+ and indirectly enhancing the dearsenification of arsenopyrite.

Bacterial nitric oxide reductase (NorBC) models employing click chemistry

Bacterial NO Reductase (NorBC or cNOR) is a membrane-bound enzyme found in denitrifying bacteria that catalyzes the two-electron reduction of NO to N2O and water. The mechanism by which NorBC operates is highly debated, due to the fact that this enzyme is difficult to work with, and no intermediates of the NO reduction reaction could have been identified so far. The unique active site of NorBC consists of a heme b3/non-heme FeB diiron center. Synthetic model complexes provide the opportunity to obtain insight into possible mechanistic alternatives for this enzyme. In this paper, we present three new synthetic model systems for NorBC, consisting of a tetraphenylporphyrin-derivative clicked to modified BMPA-based ligands (BMPA = bis(methylpyridyl)amine) that model the non-heme site in the enzyme. These complexes have been characterized by EPR, IR and UV–Vis spectroscopy. The reactivity with NO was then investigated, and it was found that the complex with the BMPA-carboxylate ligand as the non-heme component has a very low affinity for NO at the non-heme iron site. If the carboxylate functional group is replaced with a phenolate or pyridine group, reactivity is restored and formation of a diiron dinitrosyl complex was observed. Upon one-electron reduction of the nitrosylated complexes, following the semireduced pathway for NO reduction, formation of dinitrosyl iron complexes (DNICs) was observed in all three cases, but no N2O could be detected.

The effect of biochemical oxidation on the hydrometallurgical production of copper

The article presents the results of the use of the biochemical leaching method for copper-bearing non-commercial ore in a full hydrometallurgical cycle. The object of the study was the average copper-bearing ore of the Satbayev deposit, with an initial copper content of 0.26%. The experimental part of the full hydrometallurgical cycle included percolation leaching, extraction, and re-extraction tests, as well as electrodeposition tests and the production of finished cathode copper. Two variants of percolation leaching were performed as a comparison: a standard method using only sulfuric acid and a preliminary bacterial oxidation method for mineral raw materials with an adapted bacterial strain, Acidithiobacillus ferrooxidans. Percolation leaching experiments showed a significant reduction in sulfuric acid consumption when preliminary bacterial oxidation was used. Upon reaching the level of copper extraction from the ore of 86–87%, the final consumption of sulfuric acid for the standard leaching method was 15.5 kg per ton, while 9.4 kg per ton was required for the biochemical method. The productive solution obtained in the biochemical leaching process showed full suitability for all technological stages of hydrometallurgical copper production.

Bacterial cell-free metabolites-based zinc oxide nanoparticles for combating skin-causing bacterial infections

Recently, the development of skin barrier depend on wound healing, which is one of the most complicated biological processes. As an alternative to conventional antibiotics, nanoparticles (NPs) have become more utilized generally to attack bacteria. Due to their distinct characteristics, potential microbicidal action, and ability to speed up the wound healing process, zinc oxide nanoparticles (ZnO-NPs) have attracted much attention. Biological techniques can solve the restrictions of both physical and chemical approaches for nanoparticles synthesis. Because it does not require expensive chemicals, high temperatures, or a lot of time, biological synthesis is relatively easy, inexpensive, and environmentally benign. The secondary metabolic extract from Escherichia coli was used in this study to biologically synthesize three distinct quantities of ZnO-NPs, which were then assessed for their effectiveness in wound healing and bacterial infection prevention. The biofabricated ZnO-NPs were fully characterized in terms of particle shape, morphology, and stability against aggregation. Depending on the concentration of the utilized zinc salt, three different samples were fabricated biologically, nominated as ZnO-NPs-1, ZnO-NPs-2, and ZnO-NPs-3. The findings of Uv-vis absorption peaks were obtained at 352 nm, demonstrating the preparation of ZnO-NPs. The results demonstrated the formation of ZnO-NPs with an average particle size of 79.19, 79.83 and 91.57 nm for the three prepared samples (ZnO-NPs-1, ZnO-NPs-2, and ZnO-NPs-3), respectively. Additionally, these samples of ZnO-NPs exhibited zeta potential values around −34.3, −33.7, and −33.4 mV, respectively. Energy dispersive X-ray confirmed the successful formation of ZnO-NPs. It was also observed from the obtained results that, ZnO-NP-3 showed superior antimicrobial potential against selected skin infectious microbes. The effective killing dosage of ZnO-NPs-3 was recorded to be 40 mg/L which can eliminate microbial growth. The dysregulation of skin flora significantly influences the etiology of inflammatory skin disorders.

Citric Acid Confers Broad Antibiotic Tolerance through Alteration of Bacterial Metabolism and Oxidative Stress.

Antibiotic tolerance has become an increasingly serious crisis that has seriously threatened global public health. However, little is known about the exogenous factors that can trigger the development of antibiotic tolerance, both in vivo and in vitro. Herein, we found that the addition of citric acid, which is used in many fields, obviously weakened the bactericidal activity of antibiotics against various bacterial pathogens. This mechanistic study shows that citric acid activated the glyoxylate cycle by inhibiting ATP production in bacteria, reduced cell respiration levels, and inhibited the bacterial tricarboxylic acid cycle (TCA cycle). In addition, citric acid reduced the oxidative stress ability of bacteria, which led to an imbalance in the bacterial oxidation-antioxidant system. These effects together induced the bacteria to produce antibiotic tolerance. Surprisingly, the addition of succinic acid and xanthine could reverse the antibiotic tolerance induced by citric acid in vitro and in animal infection models. In conclusion, these findings provide new insights into the potential risks of citric acid usage and the relationship between antibiotic tolerance and bacterial metabolism.

Nanobioremediation: a bacterial consortium-zinc oxide nanoparticle-based approach for the removal of methylene blue dye from wastewater.

Industrial effluents carrying dyes are considered a major environmental threat in the present era. Methylene blue (MB) dye is one of the key dyes of the thiazine group of dyes. It is broadly used in medical, textile, and various fields and is well known for its carcinogenicity and methemoglobin nature. Bacterial and other microbes-mediated bioremediation is becoming an emerging and significant section for the treatment of wastewater. Isolated bacteria were used for the bioremediation and nanobioremediation of methylene blue dye under varying conditions and parameters. A comparative study was conducted for the remediation of methylene blue dye using bacterial consortium, potential bacteria (isolated by scale-up method), and potential bacteria within zinc oxide nanoparticles. The decolorizing ability of bacteria was analyzed by UV visible spectrophotometer after stirring and static incubation in different time intervals of the isolates. Growth parameters and environmental parameters which include pH, initial dye concentration, and dose of nanoparticles were optimized with the minimal salt medium. An enzyme assay study was also done to check the effect of dye and nanoparticles on bacterial growth and the mode of action of degradation. The authors found that potential bacteria within ZnO nanoparticles showed enhanced decolorization efficiency (95.46% at pH 8) due to the properties of nanoparticles. On the other hand, the decolorization of MB dye by potential bacteria and the bacterial consortium was about 89.08 and 76.3%, respectively, for a 10-ppm dye concentration. During the enzyme assays study, the highest activity was observed for phenol oxidase, nicotinamide adenine dinucleotide (NADH), 2,6-Dichloroindophenol(DCIP), and laccase for nutrient broth having MB dye, MB dye, and ZnO NPs, while no such change was observed for manganese peroxidase enzyme activity. Nanobioremediation is a promising approach to removing such pollutants from the environment.

A Comparative Study on Bioleaching Properties of Various Sulfide Minerals Using Acidiphilium cryptum

Bioleaching has been regarded as a green alternative to chemical leaching in metal extraction processes. In this study, the bioleaching properties of indigenous acidophilic bacteria for various sulfide minerals were compared and evaluated in terms of pH reduction and metal leaching. The primary minerals in the samples were sphalerite (ZnS) (SP), galena (PbS) (GN1 and GN2), pyrite (FeS2) (PY), and chalcopyrite (CuFeS2) (CCP), and an indigenous acidophilic bacterium, Acidiphilium cryptum (99.56%), was applied for bioleaching experiments. The metal extraction in bioleaching differed according to the mineral content. The leached metal concentration of Zn was higher than that of Pb for the SP sample with a high ZnS content, whereas the concentration of Pb was higher than that of Zn for the GN1 and GN2 samples with a high PbS content. Meanwhile, the leaching rate of Zn was faster than that of Pb for all samples. Corrosion action was observed on the surface of bacterial residues in SP and GN1 samples. These results show that the bioleaching mechanism based on sulfide minerals proceeds through indirect biological oxidation, chemical oxidation, and direct bacterial oxidation. The results of this study can provide basic research data for process optimization when employing bioleaching to extract valuable metals.

Two modes of gypsum replacement by carbonate and native sulfur in the Lorca Basin, SE Spain

Organoclastic sulfate reduction and bacterial sulfide oxidation have been suggested to explain the formation of authigenic carbonate and native sulfur replacing gypsum in the Lorca Basin, Spain. To gain more insight into the nature of this replacement, two types of sulfur-bearing carbonate (laminated and brecciated) from the late Miocene Lorca Basin were studied. Petrographic observations revealed that a sulfur-bearing laminated carbonate consists of clay-rich and dolomite-rich laminae with carbonate and native sulfur pseudomorphs after gypsum. Positive δ18Ocarbonate values in the laminae (δ18O = 2.6‰) and lipid biomarkers of halophilic archaea (e.g., extended archaeol) suggest formation under hypersaline conditions. Bacterial sulfate reduction, evidenced by biomarkers such as iso-C15, iso-C16, and iso-C17 fatty acids, produced hydrogen sulfide inducing the abiotic formation of organic sulfur compounds. Gypsum in the laminated carbonate likely dissolved due to undersaturation as evidenced by a low content of carbonate-associated sulfate (3,668 ppm) and 34S-enriched native sulfur (δ34S = 22.4‰), reflecting sulfate limitation. Such 34S-enrichment implies limited fluid flow, which probably restricted the supply of molecular oxygen required for native sulfur formation through oxidation of hydrogen sulfide. Alternatively, sulfate-reducing bacteria may have mediated native sulfur formation directly as a stress response to environmental conditions. The formation of sulfur-bearing calcite in brecciated carbonates is due to post-depositional alteration. Negative δ18O values of the calcite (δ18O = −1.5‰) and a tenfold decrease in carbonate-associated sulfate content (752 ppm) suggest gypsum dissolution and subsequent calcite precipitation from meteoric water. Relatively 34S-depleted native sulfur (δ34S = 13.1‰) leaves it ambiguous whether meteoric water influx could have supplied sufficient molecular oxygen for oxidation of hydrogen sulfide. In case of the brecciated carbonate, methanogenesis, anaerobic oxidation of methane, and bacterial sulfate reduction apparently mediated the formation of secondary minerals as indicated by 13C-depleted lipid biomarkers representative for the respective metabolisms. This study reveals that the conditions and timing of gypsum replacement are variable–taking place 1) during or shortly after gypsum deposition or 2) significantly after sedimentation–and suggests that methanogens in addition to anaerobic methanotrophic archaea and sulfate-reducing bacteria may be involved in the mineral-forming processes in the sedimentary subsurface.

MODELING AND ADJUSTMENT OF A FUZZY CONTROLLER IN A BIOREACTOR CONTROL SYSTEM

The article describes the modeling and configuration of a fuzzy controller for the control system of the bacterial oxidation of hard-to-enrich gold-bearing sulfide ores. The simulated logical fuzzy controller allows you to save the consumption of refrigerant water consumed in the process by 4,3%, using it to control the process of bacterial oxidation.

The Use of Bio-Manufactured Nano-Zinc from Bacillus cereus in the Control of Dreshslera oryzae Fungus

This research set out to create biosynthetic nano zinc ZnO-NPs by employing Bacillus cereus, characterize said nano zinc, and then test said nano zinc’s ability to thwart the spread of Dreshslera oryzae, the fungus responsible for rice’s brown spot disease. Bacillus cereus was used in a biological process to produce nano-sized zinc oxide, and this nano-sized zinc was then analyzed using a number of different methods. The ZnO-NPs generated from B. cereus had a nano zinc size of 22.48 nm, and their UV-Spectrophotometer examination indicated a significant absorption peak at 390 nm. Furthermore, the X-ray diffraction (XRD) results demonstrated that the particles are crystalline in nature. The Scanning Electron Microscope (SEM) analysis confirmed that the ZnO-NP produced by the B. cereus bacteria are well coordinated, mostly spherical, and somewhat homogenous in size (ranging from 37 nm). Taking a three-dimensional image with the atomic force microscopes also confirmed the surface form of the bacterial bio-zinc oxide nanoparticles (AFM). It was also determined that a concentration of 20 g/ml of nano zinc is optimal for preventing the growth of the fungus D. oryzae, which is responsible for the brown spot disease on rice. ZnO-NPs derived from B. cereus completely inhibited the growth of all of the tested fungal isolates, while the control treatment had no effect.

Alteration of sulfide ore of the Samolazovskoe deposit, Aldan shield, in an experimental bioleaching heap

The article contains the results of a mineralogical study of sulfide ores of the Samolazovskoe deposit (Aldan Shield) and the products of their experimental bacterial oxidation in a heap. Pyrite and marcasite are the major minerals of primary ores. They form fine-grained crystalline and micrometer-grained to cryptocrystalline aggregates. Sphalerite, galena, chalcopyrite, pyrrhotite, fahlore, luzonite, bournonite and other Sb sulfosalts, antimonite, arsenopyrite are minor minerals. Tiemannite, coloradoite, calaverite, hessite, petzite and native gold are rare. The ores in the experimental biooxidation heap are mostly altered in its upper parts. The secondary products of the alteration of ores include fine-grained Mg- and S-bearing calcite, smectites after feldspars, and films of Fe3+oxyhydroxides on the surface and in fractures of ore. In the lower part of the heap, technogenic processes are weak and mainly include the formation of gypsum . The sulfides are preserved throughout the heap vertical profile including very fine crystalline, colloform and botryoidal aggregates with a nonstoichiometric ratio of cations and anions and the presence of As, Ni and Cu. The botryoidal aggregates of the Fe disulfides contain galena, which forms a “microseptary” structure, which was not found in primary ores. The high-fineness native gold was found in assemblage with coloradoite and calaverite as inclusions in fine-grained aggregates of Fe disulfides. The conclusion is made on an insufficient impact of the bioleaching of refractory ores in the irrigation regime used, and forming of the secondary minerals that prevent the extraction of gold. Keywords: Samolazovskoe deposit, Aldan Shield, coloradoite, calaverite, native gold, refractory ores, bio-oxidation.