Metabolic Capabilities of Sulfur Oxidizing Bacteria and Their Role in Water Pollution

This report describes investigations into the physiology of microorganisms that are commonly involved in the oxidation of inorganic sulfur compounds. The metabolic activities of these bacteria play a potent role in several fields of economic importance such as strip mining operations, water pollution, corrosion, metallurgy, petroleum technology and soil fertility processes. The oxidation of inorganic sulfur compounds was studied in the chemolithotrophs Thiobacillus denitrificans, Thiobacillus A2, Thiobacillus neapolitanus, and a photolithotroph Rhodopseudomonas palustris. Cell suspensions from all of the thiobacilli catalyzed completely the oxidation of sulfide, thiosulfate, and sulfite to sulfate. The oxidation of thiosulfate in R. palustris was light-dependent and involved tetrathionate and trithionate as the major intermediates in the formation of sulfates. Almost all of the thiobacilli (e.g. T. neapolitanus and T. denitrificans) were capable of producing approximately 7.5 moles of sulfuric acid aerobically from 3.75 moles of thiosulfate per gram of cellular protein per hr. By far the most prolific producer of sulfuric acid (or sulfates) from the anaerobic thiosulfate oxidation with nitrates was T. denitrificans which was capable of producing 15 moles of sulfates from 7.5 moles of thiosulfate with concomitant reduction of 12 moles of nitrate resulting in the evolution of 6 moles of nitrogen gas/g protein/hr. The oxidation of sulfide was mediated by the flavoprotein system and cytochromes of b, c, o, and a-type. This process was sensitive to flavoprotein inhibitors, antimycin A, and cyanide. Thiosulfate oxidation, on the other hand involved cytochrome c:02 oxidoreductase region of the electron transport chain and was sensitive to cyanide only. The anaerobic oxidation of thiosulfate by T. denitrificans, however, was severely inhibited by the flavoprotein inhibitors because of the splitting of the thiosulfate molecule into the sulfide and sulfite moieties produced by the thiosulfate-reductase. Accumulation of tetrathionate and to a small extent trithionate and pentathionate occurred during anaerobic growth of T. denitrificans. These polythionates were subsequently oxidized to sulfate with the concomitant reduction of nitrate to N2. Intact cell suspensions catalyzed the complete oxidation of sulfide, thiosulfate, tetrathionate, and sulfite to sulfate with the stiochiometric reduction of nitrate, nitrite, nitric oxide, and nitrous oxide to nitrogen gas thus indicating that NO2, NO, and N2O are the possible intermediates in the denitrification of nitrate. This process was mediated by the cytochrome electron transport chain and was sensitive to the electron transfer inhibitors. In addition, the APS-reductase pathway was also operative. The latter aspect was absent in T. novellus and Thiobacillus-A2. In all of the thiobacilli the inner as well as the outer sulfur atoms of thiosulfate were oxidized at approximately the same rate by intact cells. The sulfide oxidation occurred in two stages: (1) a cellular-membrane-associated initial and rapid oxidation reaction which was dependent upon sulfide concentration, and (2) a slower oxidation reaction stage catalyzed by the cell-free extracts, probably involving polysulfides. In T. novellus and T. neapolitanus the oxidation of inorganic sulfur compounds is coupled to energy generation through oxidative phosphorylation, however, the reduction of pyridine nucleotides by sulfur compounds involved an energy-linked reversal of electron transfer

Metabolic Role of Sulfates and Sulfides Producing Bacteria in Pollution of Waters

Cytochrome transport particles from Nitrobacter catalyzed nitrite, ascorbate as well as NADH oxidation with concomitant phosphate esterification yielding P/0 ratios of 1.0, 0.6 and 2.0 respectively. Phosphorylation coupled to nitrite oxidation was not effected by rotenone, amytal or antimycin while 50 and 70% inhibition of the NADH-linked phosphorylation was observed in the presence of HOQNO and rotenone respectively. Cell-free extracts from Nitrobacter also catalyzed an energy-dependent reduction of NAD+ by nitrite. The reduction of cytochrome c by NŌ2 was energy-dependent which involved the reversal of electrons from cytochrome a1. The subsequent energy-linked reduction of the flavoproteins and pyridine nucleotides occurred concomitantly with the oxidation of cytochrome c. The process of energy-linked reversal of electron transfer in Nitrobacter was markedly sensitive to all the inhibitors and uncouplers. The reduction of NAD+ by thiosulfate in T. neapolitanus was an energy-linked process and involved the reversal of electrons from ferrocytochrome c mediated by flavoproteins. Cell-free extracts also catalyzed the reduction of NAD+ by sultie at the expense of ATP and involved the participation of the flavoprotein-pyridine nucleotide segment of the respiratory chain. The NADH oxidation by T. neapolitanus was mediated by the flavoprotein and cytochrome systems and this process also appeared to be coupled with energy-generation. The energy-dependent metabolism of sulfate producing bacteria and nitrite oxidizing bacteria was found to be very markedly sensitive to extremely low quantities of chloro, bromo or nitre-substituted phenols. Investigations which were conducted to assess the importance of these organisms in natural environments seem to be rather important in designing control measures for the control of biological production of sulfur or nitrogen compounds or acidity in acid-mine streams or spoil bank

CSF oligoclonal bands in multiple sclerosis

Objective: To study the significance of oligoclonal bands in neurological disorders, specifically in Multiple Sclerosis (MS). Methods: The study was designed to assess the sensitivity and specificity of the test methodology of CSF electrophoresis by performing the retrospective analysis of CSF samples sent for oligoclonal bands (OCB). A total of 603 samples were received by the Clinical Laboratories, Department of Pathology of The Aga Khan University, during a period of 54 months (January 1993-June 1997). All of these samples were analyzed by performing CSF protein electrophoresis. One hundred thirty three out of 603 samples showed evidence of OCB. Out of these, 24 patients were registered with Section of Neurology, Department of Medicine, The Aga Khan University Hospital. These 24 patients were finally selected for analysis. Relevant clinical details such as age, sex and clinical presentations were recorded. Results: Fifteen (62%) out of 24 patients with positive OCB were diagnosed as cases of MS. Four (17%) patients were diagnosed to have subacute sclerosing panencephalitis (SSPE). Five (21%) patients were having other inflammatory neurological disorders. Conclusion: The overall relative sensitivity and specificity for multiple sclerosis were found to be 100% and 62.5% respectively. Lack of specificity was attributed to the fact that OCB were positive in other neurological disorders as well

Performance of grid-connected solar photovoltaic systems with single-tuned and double-tuned harmonic passive filters

The generated solar photovoltaic power can be stand-alone or grid-connected. In both systems, power quality issues arise and can affect the network. The harmonic distortions can affect the system significantly if they are not mitigated. This paper presents the performance of grid-connected solar photovoltaic systems with single-tuned and double-tuned filters for harmonics mitigation. The design aspects of each filter are presented and discussed. The simulation results are analyzed and validated using ETAP software

Agent-based simulations on Catalan interprovincial migrations

This work contemplates the phenomenon of migration related to economic reasons. Firstly, the foundations of a mathematical model are laid down, which have key departure points that mold the approach for doing the rest of the thesis. Secondly, a statistical model on the probability of Catalan interprovincial migrations is displayed. Finally, a NetLogo model is used to simulate the Catalan interprovincial migrations, more specifically, return migrations throughout the period 2008-2020.Este trabajo contempla el fenómeno de la migración relacionado con motivos económicos. En primer lugar, se establecen las bases de un modelo matemático, que tiene puntos de partida claves que moldearon el enfoque para hacer el resto de la tesis. En segundo lugar, se muestra un modelo estadístico sobre la probabilidad de las migraciones interprovinciales catalanas. Finalmente, se utiliza un modelo hecho con NetLogo para simular las migraciones interprovinciales catalanas, más concretamente, las migraciones de retorno a lo largo del periodo 2008-2020

Optimal network reconfiguration in active distribution networks with soft open points and distributed generation

Copyright © 2019 by the authors. In this study, we allocated soft open points (SOPs) and distributed generation (DG) units simultaneously with and without network reconfiguration (NR), and investigate the contribution of SOP losses to the total active losses, as well as the effect of increasing the number of SOPs connected to distribution systems under different loading conditions. A recent meta-heuristic optimization algorithm called the discrete-continuous hyper-spherical search algorithm is used to solve the mixed-integer nonlinear problem of SOPs and DGs allocation, along with new NR methodology to obtain radial configurations in an efficient manner without the possibility of getting trapped in local minima. Further, multi-scenario studies are conducted on an IEEE 33-node balanced benchmark distribution system and an 83-node balanced distribution system from a power company in Taiwan. The contributions of SOP losses to the total active losses, as well as the effect of increasing the number of SOPs connected to the system, are investigated to determine the real benefits gained from their allocation. It was clear from the results obtained that simultaneous NR, SOP, and DG allocation into a distribution system creates a hybrid configuration that merges the benefits offered by radial distribution systems and mitigates drawbacks related to losses, power quality, and voltage violations, while offering a far more efficient and optimal network operation. Also, it was found that the contribution of the internal loss of SOPs to the total loss for different numbers of installed SOPs is not dependent on the number of SOPs and that loss minimization is not always guaranteed by installing more SOPs or DGs along with NR. One of the findings of the paper demonstrates that NR with optimizing tie-lines could reduce active losses considerably. The results obtained also validate, with proper justifications, that SOPs installed for the management of constraints in LV feeders could further reduce losses and efficiently address issues related to voltage violations and network losses

Big data optimization in electric power systems: a review

There are different definitions of big data, and among them, the most common definition refers to three or five characteristics, called volume, velocity, variety, value, and veracity from (Laney (2001)). Volume could include Tera Byte, Peta Byte, Exa Byte, and Zetta Byte. Velocity describes how fast the data are retrieved and processed ‘‘Batch or streaming”. Variety describes structured, semi-structured, and unstructured data (Laney, 2001, Zikopoulos and Eaton, 2011). Veracity explains the integrity and disorderliness of data, while value refers to how good is the “value” we derive from analyzing data? (Zicari et al., 2016). Electrical power systems are networks of components arrayed to supply, transfer, and use electric power. In power system since models are used to predict and characterize operations. However, there is a necessity for powerful optimization algorithms for information processing to learn models as the size increase of data is becoming a global problem to solve large-scale optimization problems. Any optimization problem includes a real function to be maximized or minimized by systematically determination of input values from an allowed set of values. Richness and quantity of large data sets provide the potential to enhance statistical learning performance but require smart models that use the latent low-dimensional structure for effective 2 data separation. This chapter reviews the most recent scientific articles related to large and big data optimization in power systems. Optimization issues such as logistics in power systems and techniques including nonsmooth, nonconvex, and unconstrained large-scale optimization are presented. After a brief review of big data, scientometric analysis has been applied using keywords of “big data” and “power system.” Besides, keywords analysis, network visualization, journal map, and bibliographic coupling analysis have been done to draw a path on big data works in power system problems. Also, the most common useful techniques in large-scale optimization in power system have been reviewed. At the end of this chapter, metaheuristic techniques in big data optimization are reviewed to show that many efforts have been involved in big data optimization in power system and systematically highlight some perspectives on big data optimization

A polishing the harmful effects of Broad Bean Mottle Virus infecting broad bean plants by enhancing the immunity using different potassium concentrations

Broad bean mottle virus (BBMV) infects a wide range of hosts, resulting in significant production reductions. The lack of adequate and effective control methods involves implementing novel BBMV control strategies. Herein, we demonstrate the effect of different potassium concentrations (20, 40, and 60 mM) against BBMV in broad bean plants. Potassium could control BBMV infection in broad bean by inhibiting the virus. In addition, infection with BBMV caused a significant decrease in morphological criteria, SPDA, photosynthetic characteristics, phytohormones, and mineral content in broad bean leaves compared to control plants. The levels of reactive oxygen species (ROS) (hydrogen peroxide, hydroxyl radical, and oxygen anion) and ROS scavenging enzymes (catalase, superoxide dismutase, peroxidase, phenylaniline ammonia-lyase, chitinase, and 1,3 - glucanase) increased significantly in plants inoculated with BBMV alone or in the presence of K+. In addition, proline and phenolic compounds increased significantly after being infected with BBMV. In conclusion, treatment with a high potassium concentration (60 mM) alleviates the adverse effect of BBMV on broad bean plants by boosting secondary metabolites, phytohormones, and enzymatic antioxidants

Development of Liposomal Gemcitabine with High Drug Loading Capacity

Liposomes are widely used for systemic delivery of chemotherapeutic agents to reduce their nonspecific side effects. Gemcitabine (Gem) makes a great candidate for liposomal encapsulation due to the short half-life and nonspecific side effects; however, it has been difficult to achieve liposomal Gem with high drug loading capacity. Remote loading, which uses a transmembrane pH gradient to induce an influx of drug and locks the drug in the core as a sulfate complex, does not serve Gem as efficiently as doxorubicin (Dox) due to the low pKa value of Gem. Existing studies have attempted to improve Gem loading capacity in liposomes by employing lipophilic Gem derivatives or creating a high-concentration gradient for active loading into the hydrophilic cores (small volume loading). In this study, we combine the remote loading approach and small volume loading or hypertonic loading, a new approach to induce the influx of Gem into the preformed liposomes by high osmotic pressure, to achieve a Gem loading capacity of 9.4–10.3 wt % in contrast to 0.14–3.8 wt % of the conventional methods. Liposomal Gem showed a good stability during storage, sustained-release over 120 h in vitro, enhanced cellular uptake, and improved cytotoxicity as compared to free Gem. Liposomal Gem showed a synergistic effect with liposomal Dox on Huh7 hepatocellular carcinoma cells. A mixture of liposomal Gem and liposomal Dox delivered both drugs to the tumor more efficiently than a free drug mixture and showed a relatively good anti-tumor effect in a xenograft model of hepatocellular carcinoma. This study shows that bioactive liposomal Gem with high drug loading capacity can be produced by remote loading combined with additional approaches to increase drug influx into the liposomes

Hepatitis C virus cell-cell transmission and resistance to direct-acting antiviral agents

Hepatitis C virus (HCV) is transmitted between hepatocytes via classical cell entry but also uses direct cell-cell transfer to infect neighboring hepatocytes. Viral cell-cell transmission has been shown to play an important role in viral persistence allowing evasion from neutralizing antibodies. In contrast, the role of HCV cell-cell transmission for antiviral resistance is unknown. Aiming to address this question we investigated the phenotype of HCV strains exhibiting resistance to direct-acting antivirals (DAAs) in state-of-the-art model systems for cell-cell transmission and spread. Using HCV genotype 2 as a model virus, we show that cell-cell transmission is the main route of viral spread of DAA-resistant HCV. Cell-cell transmission of DAA-resistant viruses results in viral persistence and thus hampers viral eradication. We also show that blocking cell-cell transmission using host-targeting entry inhibitors (HTEIs) was highly effective in inhibiting viral dissemination of resistant genotype 2 viruses. Combining HTEIs with DAAs prevented antiviral resistance and led to rapid elimination of the virus in cell culture model. In conclusion, our work provides evidence that cell-cell transmission plays an important role in dissemination and maintenance of resistant variants in cell culture models. Blocking virus cell-cell transmission prevents emergence of drug resistance in persistent viral infection including resistance to HCV DAAs