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Streptococcus dysgalactiae infection can cause bovine mastitis and lead to huge economic losses for the dairy industry. The abuse of antibiotics has resulted in growing drug resistance of S. dysgalactiae, which causes hard-to-treat infections. Bacteriophage lysin, as a novel antibacterial agent, has great potential for application against drug-resistant gram-positive bacteria. However, few studies have been conducted on the prophage lysin of S. dysgalactiae. In this study, we mined a novel prophage lysin, named Lys1644, from a clinical S. dysgalactiae isolate by genome sequencing and bioinformatic analysis. Lys1644 was expressed and purified, and the lytic activity, antibacterial spectrum, optimal pH and temperature, lytic activity in milk in vitro, and synergistic bacteriostasis with antibiotics were assessed. The Lys1644 prophage lysin showed high bacteriolysis activity specifically on S. dysgalactiae, which resulted in CFU 100-fold reduction in milk. Moreover, Lys1644 maintained high activity over a wide pH range (pH 5-10) and a wide temperature range (4-42 °C). Synergistic bacteriostatic experiments showed that the combination of low-dose Lys1644 (50 µg/mL) with a subinhibitory concentration of aminoglycoside antibiotics (kanamycin or spectinomycin) can completely inhibit bacterial growth, suggesting that the combination of Lys1644 and antibiotics could be an effective therapeutic strategy against S. dysgalactiae infection.
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Antibacterianos , Profagos , Streptococcus , Streptococcus/efectos de los fármacos , Profagos/genética , Antibacterianos/farmacología , Antibacterianos/química , Animales , Leche/microbiología , Fagos de Streptococcus/genética , Bovinos , Mastitis Bovina/microbiología , Mastitis Bovina/tratamiento farmacológico , Concentración de Iones de Hidrógeno , Bacteriólisis/efectos de los fármacos , Infecciones Estreptocócicas/microbiología , Infecciones Estreptocócicas/tratamiento farmacológicoRESUMEN
Advanced oxidation technologies based on peroxymonosulfate (PMS) have been extensively applied for the degradation of antibiotics. However, the degradation process inevitably introduces SO42- and other sulfur-containing anions, these pollutants pose a huge threat to the water and soil environment. Addressing these concerns, this study introduced PMS oxidation into a multi-chamber membrane capacitive deionization (MC-MCDI) device to achieve simultaneous tetracycline (TC) degradation and removal of PMS reaction byproduct ions. The experimental results demonstrated that when the TC solution (40 mg L-1) was pre-adsorbed for 10 min, the voltage was 1.2 V and the concentration of PMS solution added was 4 mg mL-1, the removal efficiency of TC and ion can reach 77.4 % and 46.5 % respectively. Furthermore, the activation process of PMS in MC-MCDI/PMS system and the reactive oxygen (ROS) that mainly produce degradation were deeply investigated. Finally, liquid chromatography-mass spectrometry (LC-MS) was employed to identify intermediates of TC degradation, propose potential degradation pathways, and analyze the toxicities of the intermediates. In addition, in five cycles, the MC-MCDI/PMS system demonstrated excellent stability. This study provides an effective strategy for treating TC wastewater and a novel approach for simultaneous TC degradation and desalination.
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Oxidación-Reducción , Peróxidos , Tetraciclina , Contaminantes Químicos del Agua , Purificación del Agua , Tetraciclina/química , Contaminantes Químicos del Agua/química , Purificación del Agua/métodos , Peróxidos/química , Antibacterianos/química , Membranas Artificiales , Especies Reactivas de Oxígeno/químicaRESUMEN
Excess sludge (ES), a resource-rich organic waste, can be solubilized by thermophilic enzymes to extract proteins for sludge reduction and resources recovery. To solve the problems of low hydrolysis effect of ES and low enzyme producing ability of wild thermophilic bacteria, ultraviolet and diethyl sulfate (UV-DES) were adopted to mutate thermophilic bacteria in this study. Mutation sites were detected and annotated by whole genome sequencing analysis. The results showed that UV-DES mutagenesis could effectively improve enzyme-producing capacity of thermophilic bacteria and promote the hydrolysis of ES. The protease activity of the mutant strain KT16 was 46.7 % higher than that of the original strain DC8. The protein extraction rate with enzyme produced by KT16 reached 83.3 %. The total content of proteins recycled through KT16 enzyme solution was 3539.6 mg·L-1, 18.4 % higher than that of DC8. This work provided a theoretical idea and technical guidance for the protein recovery from ES.
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Péptido Hidrolasas , Aguas del Alcantarillado , Ésteres del Ácido Sulfúrico , Aguas del Alcantarillado/microbiología , Péptido Hidrolasas/genética , Endopeptidasas , Hidrólisis , Proteínas , Bacterias/genética , Mutación/genética , Eliminación de Residuos Líquidos/métodosRESUMEN
The process of intracellular proteolysis through ATP-dependent proteases is a biologically conserved phenomenon. The stress responses and bacterial virulence of various pathogenic bacteria are associated with the ATP-dependent Clp protease. In this study, a Brucella abortus 2308 strain, ΔclpP, was constructed to characterize the function of ClpP peptidase. The growth of the ΔclpP mutant strain was significantly impaired in the TSB medium. The results showed that the ΔclpP mutant was sensitive to acidic pH stress, oxidative stress, high temperature, detergents, high osmotic environment, and iron deficient environment. Additionally, the deletion of clpP significantly affected Brucella virulence in macrophage and mouse infection models. Integrated transcriptomic and proteomic analyses of the ΔclpP strain showed that 1965 genes were significantly affected at the mRNA and/or protein levels. The RNA-seq analysis indicated that the ΔclpP strain exhibited distinct gene expression patterns related to energy production and conversion, cell wall/membrane/envelope biogenesis, carbohydrate transport, and metabolism. The iTRAQ analysis revealed that the differentially expressed proteins primarily participated in amino acid transport and metabolism, energy production and conversion, and secondary metabolites biosynthesis, transport and catabolism. This study provided insights into the preliminary molecular mechanism between Clp protease to bacterial growth, stress response, and bacterial virulence in Brucella strains.
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Péptido Hidrolasas , Animales , Ratones , Brucella abortus/genética , Endopeptidasa Clp/genética , Proteómica , Virulencia , Modelos Animales de EnfermedadRESUMEN
In order to tackle the issue of terramycin mycelial dreg (TMD) diagnosis and removal of terramycin and antibiotic resistance genes (ARGs), this study adopted aerobic composting (AC) technology and added homemade compound microbial inoculum (HCMI) to promote the AC of TMD and enhance the removal of terramycin and ARGs. The findings demonstrated that terramycin residue could be basically harmless after AC. Moreover, HCMI not only reduced QacB and tetH but also increased the degradation rates of VanRA, VanT, and dfrA24 by 40.81%, 5.65%, and 54.18%, respectively. The HCMI improved the removal rate of ARG subtypes to a certain extent. According to redundancy analysis, during AC, the succession of the microbial community had a stronger influence on the variance of ARG subtype than the environmental conditions. Differences in the abundance of various bacteria due to changes in temperature may be an intrinsic mechanism for the variation of ARG subtypes.
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Compostaje , Oxitetraciclina , Antibacterianos/farmacología , Farmacorresistencia Microbiana/genética , MicelioRESUMEN
Listeria monocytogenes is a foodborne pathogen that can tolerate a variety of extreme environments. In particular, its acid resistance (AR) capability is considered one of the key factors threating food safety. Here, we employed a microbial functional genomic technology termed transposon sequencing (Tn-seq), leading to the identification of two genes involved in cell wall peptidoglycan biosynthesis (murF) and phosphate transport (lmo2248) that play key roles in lactic acid resistance (LAR) of L. monocytogenes. Deletion of lmo2248 significantly impaired the ability of LAR in L. monocytogenes, demonstrating the accuracy of the Tn-seq results. Transcriptome analysis revealed that 31.7% of the L. monocytogenes genes on the genome were differentially expressed under lactic acid (LA) treatment, in which genes involved in phosphate transport were influenced most significantly. These findings shed light on the LAR mechanisms of L. monocytogenes, which may contribute to the development of novel strategies against foodborne pathogens. IMPORTANCE Listeria monocytogenes is a Gram-positive foodborne pathogen with high lethality and strong stress resistance, and its strong acid tolerance leads to many foodborne illnesses occurring in low-pH foods. Lactic acid is a generally recognized as safe (GRAS) food additive approved for use by the FDA. However, the genetic determinants of lactic acid resistance in L. monocytogenes have not been fully identified. In this study, the lactic acid resistance determinants of L. monocytogenes were comprehensively identified by Tn-seq on a genome-wide scale. Two genes, murF (cell wall peptidoglycan biosynthesis) and lmo2248 (phosphate transport), were identified to play an important role in the lactic acid resistance. Moreover, genome-wide transcriptomic analysis showed that phosphotransferase system (PTS)-related genes play a key role at the transcriptional level. These findings contribute to a better understanding of the lactic acid resistance mechanism of L. monocytogenes and may provide unique targets for the development of other novel antimicrobial agents.
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Listeria monocytogenes , Listeria monocytogenes/genética , Transcriptoma , Ácido Láctico , Peptidoglicano , Microbiología de Alimentos , Perfilación de la Expresión Génica , FosfatosRESUMEN
To address the problem of antibiotic mycelial dreg (AMD) treatment and removal of antibiotic resistance genes (ARGs), this study adopted anaerobic digestion (AD) technology, and added biochar (BC) and biochar loaded with nanosized zero-valent iron (nZVI-BC) to promote the AD of AMD and enhance the removal of ARGs. Results showed that nZVI-BC was better than BC in promoting AD due to the hydrogen evolution corrosion and the synergistic effect of nZVI and BC. In addition, BC and nZVI-BC can enhance the oxidative stress response and reduce ammonia stress phenomenon, which significantly reduces the abundance of aadA, ant(2â³)-â , qacEdelta1 and sul1. In conclusion, the enhance effect of nZVI-BC is greater than BC. The removal efficiency rates of nZVI-BC on the above-mentioned four ARGs were improved by 33%, 9%, 24% and 11%.
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A phosphorus removal biochar adsorbent was prepared from Fenton sludge. The adsorption process was optimized, and its phosphorus adsorption mechanism was discussed. It was found that the phosphorus adsorption performance of biochar prepared from single Fenton sludge (FBC-400) was better than that of co-pyrolysis of Fenton sludge and bamboo powder. The optimum condition was that Fenton sludge pyrolyzed at 400°C (FBC-400). FBC-400 had a larger specific surface area than that prepared by co-pyrolysis with bamboo powder. And the high content of iron element could provide a higher surface charge of the biochar, thereby increasing the electrostatic adsorption of phosphorus onto FBC-400. The phosphorus adsorption was highly pH dependent by FBC-400, which can enhance electrostatic adsorption and increase adsorption capacity in acidic conditions. The effect of coexisting anion on adsorption performance was mainly affected by CO3 2- , reducing the adsorption capacity by at least 49%, whereas other anions had no obvious interference. The adsorption process of FBC-400 accorded with the pseudo-second-order kinetic model and the Langmuir model, which indicated that the adsorption process was monolayer adsorption and mainly chemical adsorption, and the maximum saturated phosphorus adsorption capacity was 8.77 mg g-1 . The mechanisms for phosphorus adsorption were electrostatic adsorption and inner-sphere complexing. 1 M NaOH was used for desorption, and the adsorption capacity remained at 81% in the fifth cycle. PRACTITIONER POINTS: The Fenton sludge biochar usage as an adsorbent could be a win-win strategy to convert waste biomass to valuable - product. The adsorption process accorded with the Langmuir model, the maximum phosphorus adsorption capacity was 8.77 mg/g at 25°C. The adsorption mechanisms were electrostatic adsorption and inner-sphere complexing. 1M NaOH was used for desorption, and the adsorption capacity remained at 81% in the fifth cycle.
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Fósforo , Aguas del Alcantarillado , Carbón Orgánico , Polvos , Aguas del Alcantarillado/química , Hidróxido de SodioRESUMEN
Listeria monocytogenes is a major pathogen contributing to foodborne outbreaks with high mortality. Nisin, a natural antimicrobial, has been widely used as a food preservative. However, the mechanisms of L. monocytogenes involved in nisin resistance have not yet to be fully defined. A mariner transposon library was constructed in L. monocytogenes, leading to the identification of 99 genes associated with the innate resistance to nisin via Transposon sequencing (Tn-seq) analysis. To validate the accuracy of the Tn-seq results, we constructed five mutants (ΔyqgS, ΔlafA, ΔvirR, ΔgtcA, and Δlmo1464) in L. monocytogenes. The results revealed that yqgS and lafA, the lipoteichoic acid-related genes, were essential for resistance to nisin, while the gtcA and lmo1464 mutants showed substantially enhanced nisin resistance. Densely wrinkled, collapsed surface and membrane breakdown were shown on ΔyqgS and ΔlafA mutants under nisin treatment. Deletion of yqgS and lafA altered the surface charge, and decreased the resistance to general stress conditions and cell envelope-acting antimicrobials. Furthermore, YqgS and LafA are required for biofilm formation and cell invasion of L. monocytogenes. Collectively, these results reveal novel mechanisms of nisin resistance in L. monocytogenes and may provide unique targets for the development of food-grade inhibitors for nisin-resistant foodborne pathogens. IMPORTANCE Listeria monocytogenes is an opportunistic Gram-positive pathogen responsible for listeriosis, and is widely present in a variety of foods including ready-to-eat foods, meat, and dairy products. Nisin is the only licensed lantibiotic by the FDA for use as a food-grade inhibitor in over 50 countries. A prior study suggests that L. monocytogenes are more resistant than other Gram-positive pathogens in nisin-mediated bactericidal effects. However, the mechanisms of L. monocytogenes involved in nisin resistance have not yet to be fully defined. Here, we used a mariner transposon library to identify nisin-resistance-related genes on a genome-wide scale via transposon sequencing. We found, for the first time, that YqgS and LafA (Lipoteichoic acid-related proteins) are required for resistance to nisin. Subsequently, we investigated the roles of YqgS and LafA in L. monocytogenes stress resistance, antimicrobial resistance, biofilm formation, and virulence in mammalian cells.
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Proteínas Bacterianas/metabolismo , Lipopolisacáridos/metabolismo , Listeria monocytogenes/efectos de los fármacos , Listeria monocytogenes/metabolismo , Nisina/farmacología , Ácidos Teicoicos/metabolismo , Antibacterianos/farmacología , Proteínas Bacterianas/genética , Biopelículas , Enfermedades Transmitidas por los Alimentos , Regulación Bacteriana de la Expresión Génica/efectos de los fármacos , Listeria monocytogenes/genética , Listeriosis , Virulencia/efectos de los fármacosRESUMEN
Herein, a non-stacked γ-Fe2O3/C@TiO2 double-layer hollow nano photocatalyst has been developed with ultrathin nanosheets-assembled double shells for photodegradation phenol. High catalytic performance was found that the phenol could be completely degraded in 135 min under visible light, due to the moderate band edge position (VB at 0.59 eV and CB at -0.66 eV) of the non-stacked γ-Fe2O3/C@TiO2, which can expand the excitation wavelength range into the visible light region and produce a high concentration of free radicals (such as ·OH, ·O2-, holes). Furthermore, the interior of the hollow composite γ-Fe2O3 is responsible for charge generation, and the carbon matrix facilitates charge transfer to the external TiO2 shell. This overlap improved the selection/utilization efficiency, while the unique non-stacked double-layered structure inhibited initial charge recombination over the photocatalysts. This work provides new approaches for photocatalytic applications with γ-Fe2O3/C-based materials.
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Considering the complexity of traditional cobalt phosphide (Co2P) loaded biochar synthesis research on a simple and efficient synthesis method has practical significance. In this study, after phosphoric acid activation, Neosinocalamus affinis biochar (NAB) and nanoplate Co3O4 quickly formed a Co2P-NAB composite material with high Co2P crystallinity and was uniformly dispersed on the surface of NAB in a microwave reactor. Co2P-NAB has an excellent catalytic degradation effect in the activation of peroxymonosulfate (PMS) to degrade tetracycline (TC). The optimal TC degradation efficiency was achieved with the addition of 50 mg L-1 TC concentration, 0.2 g L-1 catalysts, 0.406 mM PMS and pH = 6.02. In addition, according to the pseudo-first-order reaction rate constant calculation, the composite of Co2P-NAB and PMS the synergy efficiency is 81.55 %. Compared with Co2P-NAB (10.83 %) and PMS (7.62 %) alone, the Co2P-NAB/PMS system has a significant promotion effect on the degradation of TC molecules. Additionally, the Co2P-NAB/PMS system had a TC mineralization rate of 68 % in 30 min. Furthermore, after a series of characterization, detection and analysis, and influencing factor experiments, we proposed a potential mechanism for the Co2P-NAB/PMS reaction system to degrade TC and found that singlet oxygen (1O2) plays an essential role in the non-radical degradation process. Finally, according to the liquid chromatography-mass spectrometry (LC-MS) detection of TC degradation intermediates, a possible degradation route was proposed. Therefore, this work uses microwave technology to present a novel and simple synthesis method for transition metal phosphides, which provides potential application value for the treatment of actual wastewater with heterogeneous catalysts.
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Antibacterianos , Tetraciclina , Carbón Orgánico , Concentración de Iones de Hidrógeno , PeróxidosRESUMEN
In this study, a new hollow nanotube material, 30% Co-CHNTs was prepared by the impregnation-chemical reduction-calcination method. This material can be used as a peroxymonosulfate (PMS) activator to catalyse the degradation of sulfamethoxazole (SMX). The best reaction conditions that correspond to the degradation rate of SMX, up to 97.5%, are as follows: the concentration of SMX is 10 mg L-1, the amount of catalyst is 0.20 g L-1, the dosage is 1.625 mM, and the solution pH is 6.00. X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma optical emission spectrometry (ICP-OES) show that the calcined composites mainly stimulate an increase in the content of bivalent cobalt in PMS and reduce the leaching of cobalt ions after the reaction. Additionally, the 30% Co-CHNTs + PMS reaction system exhibits a reasonable SMX degradation rate in a natural organic matter solution and excellent stability after three repeated experiments. Furthermore, the possible degradation mechanism in the 30% Co-CHNTs + PMS reaction system was analysed through electron paramagnetic resonance (EPR) and free-radical capture experiments, and it was observed that the non-radical degradation of 1O2 plays a leading role in SMX degradation. Finally, according to the nine degradation intermediates detected by liquid chromatography-mass spectrometry (LC-MS), four possible SMX degradation routes were proposed. This study proved that a 30% Co-CHNTs heterogeneous catalyst is easily prepared, inexpensive, and environmentally friendly and has potential application in antibiotic wastewater treatment.
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Nanotubos , Contaminantes Químicos del Agua , Arcilla , Cobalto , Óxidos , Peróxidos , Sulfametoxazol , Contaminantes Químicos del Agua/análisisRESUMEN
Mannosylerythritol lipids-A (MEL-A) is a novel biosurfactant with excellent surface activity and potential biomedical applications. In this study, we explored the antibacterial activity and the underlying mechanisms of MEL-A against the important food-borne pathogen Listeria monocytogenes. The bacterial growth and survival assays revealed a remarkable antibacterial activity of MEL-A. Since MEL-A is a biosurfactant, we examined the cell membrane integrity and morphological changes of MEL-A-treated bacteria by biochemical assays and flow cytometry analysis and electron microscopes. The results showed obvious damaging effects of MEL-A on the cell membrane and morphology. To further explore the antibacterial mechanism of MEL-A, a transcriptome analysis was performed, which identified 528 differentially expressed genes (DEGs). Gene ontology (GO) analysis revealed that the gene categories of membrane, localization and transport were enriched among the DEGs, and the analysis of the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways demonstrated significant changes in the maltodextrin ABC transporter system and stress response system. Furthermore, the growth of L. monocytogenes could also be significantly inhibited by MEL-A in milk, a model of a real food system, suggesting that MEL-A could be potentially applied as an natural antimicrobial agent to control food-borne pathogens in the food industry.
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Antibacterianos/farmacología , Glucolípidos/farmacología , Listeria monocytogenes/efectos de los fármacos , Antibacterianos/química , Antibacterianos/aislamiento & purificación , Glucolípidos/química , Glucolípidos/aislamiento & purificación , Listeria monocytogenes/crecimiento & desarrollo , Pruebas de Sensibilidad MicrobianaRESUMEN
Avian leukosis virus (ALV) is associated with immune suppression, neoplasia, and reduced performance in chickens. In this study, two strains of ALV were isolated from Luxi gamecocks by DF-1 cell culture and identified by PCR, immunofluorescence assay, and sequencing of the viral genome. These strains were found to be novel recombinant viruses with nucleotide sequence identity of over 93.0% in the LTR and 94.4% in U3 to ALV-J, over 95.0% in the 5'UTR to ALV-C, over 93.4% in gp85 to ALV-B, and over 96.0% in gp37 to ALV-E. These results indicate that these two isolates are recombinants between ALV-J, ALV-C, ALV-E and ALV-B.
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Virus de la Leucosis Aviar/aislamiento & purificación , Leucosis Aviar/virología , Pollos/virología , Genoma Viral , Enfermedades de las Aves de Corral/virología , Virus Reordenados/aislamiento & purificación , Animales , Virus de la Leucosis Aviar/patogenicidad , Secuencia de Bases , China , Filogenia , Virus Reordenados/patogenicidad , Análisis de Secuencia , Proteínas del Envoltorio Viral/genética , VirulenciaRESUMEN
Spinel oxides, e.g., NiCo2O4, is a promising catalyst for the catalytic oxidation of toluene. Understanding and designing versatile NiCo2O4 spinel is important for low-temperature toluene oxidation. Here, we investigated the surface-characteristic-dependent degradation activity of NiCo2O4 crystals through experiment and characterization. NiCo2O4 nanosheet using ethanol as solvent (named E--NiCo2O4) exposing {110} crystal planes exhibited the lowest temperature toluene oxidation. The T99 of toluene conversion was 256 °C, which is much lower than that of NiCo2O4 nanosheet using ethylene glycol as solvent (named EG--NiCo2O4), NiCo2O4 octahedron (named O--NiCo2O4) and NiCo2O4 truncated octahedron (named TO--NiCo2O4). Characterization using various techniques such as XRD, TEM, BET, XPS, H2-TPR and CO2-TPD showed that Co3+ and surface adsorbed oxygen (Osur) enriched surface, excellent redox properties and effective diffusion of the reaction product reasonably explain the enhancement in catalytic activity over the E--NiCo2O4. The research reveals that the effect of specific crystal planes and solvent was the key factor to govern the activity of low-temperature toluene oxidation.
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Óxido de Aluminio/química , Óxido de Magnesio/química , Tolueno/química , Adsorción , Catálisis , Frío , Oxidación-Reducción , Óxidos/química , Oxígeno/química , SolventesRESUMEN
The mineralization of organic pollutants under visible light is challenging, limiting the practical application of photocatalytic technology in wastewater treatment. To achieve the efficient mineralization of Acid red 3R (AR3R), a series of honeycombed catalysts (TiO2, C-TiO2-X, Au@TiO2 and Au@C-TiO2-X) were prepared via a facile in situ synthetic method and characterized by XRD, TEM, BET, XPS and DRS, respectively. The introduction of C and Au species promote the simultaneous generation of â¢O2- and â¢OH over Au@C-TiO2-X under visible light radiation. The Au@C-TiO2-X catalyst showed superior performance for the deep mineralization of AR3R, affording a TOC removal rate larger than 90 % within 240â¯min under visible light (> 420â¯nm). The photocatalytic degradation mechanism of AR3R is proposed according to UV-vis and in situ DRIFTS analysis. The superior photocatalytic activity of Au@C-TiO2-X is attributed to the synergistic effect of â¢O2- and â¢OH owing to C doping and Au deposition.
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In order to study their synergistic catalytic effects in toluene degradation, CuMn2O4/HTS-1 (HTS-1 was a titanium silicon molecular sieve), Cu0.7Mn2Y0.3Ox/HTS-1 and Cu0.7Mn2Ce0.3Ox/HTS-1 catalysts were prepared by the impregnation method. The textural properties, redox properties and acidity of the catalysts were characterized by X-ray diffractometer (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), H2 temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), frustrated total internal reflection (FT-IR), ammonium temperature-programmed desorption (NH3-TPD) and pyridine adsorption internal reflection (Py-IR) measurements. The potential roles of Lewis acid sites (activating dioxygen) were discussed, and the experimental results indicated that the most efficient route for toluene degradation over Cu0.7Mn2Ce0.3Ox/HTS-1 (toluene conversion rate of 90% (T99)=295°C) was ascribed to regulation of the synergistic effects of redox properties (activating molecular toluene) and Lewis acid sites (activating dioxygen). The Mars-Van-Krevelen (MVK) model was adopted to describe the reaction process of toluene oxidation, which gave an in-depth view into the toluene degradation over CuMn2O4/HTS-1, Cu0.7Mn2Y0.3Ox/HTS-1 and Cu0.7Mn2Ce0.3Ox/HTS-1. In addition, the synergistic effects between redox properties and Lewis acid sites were studied in detail.
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Modelos Químicos , Tolueno/química , Catálisis , Cobre/química , Manganeso/química , Oxidación-Reducción , Espectroscopía Infrarroja por Transformada de Fourier , TitanioRESUMEN
To efficiently treat low-concentration chromium wastewater at low cost, adsorbent iron-modified ceramsite (FCM) was successfully prepared. The adsorbent was characterized by SEM, XRD, FT-IR, XPS, ζ potential and VSM. From the experimental results, the optimum adsorption pH, adsorbent dosage and adsorption time were 4, 1g/L and 120min, respectively. The percentage removal of Cr(VI) was 93% and the reduction efficiency of Cr(VI) was 74.3% when the concentration was 2mg/L. After 5cycles, using 0.1mol/L NaOH as the regeneration agent, the removal rate of Cr(VI) did not decrease significantly. Furthermore, the mechanism of deep reduction and adsorption, the process of regeneration, the kinetics and adsorption isotherms were also explored. This paper can provide theoretical and technical support for reducing the toxicity and the advanced treatment of hexavalent chromium.
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The Brucella spp encounter stressful environment inside their host cells. The Lon protein is an important protease related to cellular protein degradation and resistance to stress in Brucella. However, the molecular mechanism between Lon protein and stress response was still unknown. In this study, it was found that the lon mutant exhibited obvious growth defect in TSB medium, compared with its parent strain. In addition, our results indicated that Lon protein was involved in resistance to various stress conditions and all the ß-lactam antibiotics tested. Although deletion of this protease did not affect Brucella virulence in macrophage, the mutant strain was significantly attenuated in mice infection model at 1 week post infection, and the expression level of several cytokine genes was significantly changed in vivo. To gain insight into the genetic basis for the distinctive phenotypic properties exhibited by the lon mutant strain, RNA-seq was performed, and the result showed that various genes involved in stress response, quorum sensing and transcriptional regulation were significantly altered in Δlon strain. Overall, these studies have preliminary uncovered the molecular mechanism between Lon protease, stress response and bacterial virulence.