Decrease In Membrane Permeability Research Articles

Advanced Treatment: Tackling Paracetamol with Fenton Oxidation and Membrane Hybrid Processes

Paracetamol (PCT) in aquatic environments has become a global concern due to its potential harm to humans and environments. However, conventional water treatment was only able to degrade PCT partially. It was necessary to treat PCT contaminated water with tertiary technologies in particular by combination approach, such as Fenton oxidation and membrane filtration process. This combined approach enabling mitigation of large chemical footprint and iron residue associated with Fenton oxidation, as well as reducing fouling tendency of the membrane. The aim of this study was to evaluate the PCT removal efficiency by hybrid technology Fenton oxidation and membrane filtration. The membrane performance during the filtration process was also analyzed. As an important parameter for Fenton process, concentration of H 2 O 2 /Fe 2+ with ratio of 1:0.5 resulted in optimal removal of 45% PCT in terms of COD removal. However, separation using flat sheet Polyethersulfone Ultrafiltration (UF) with constant flux of 120 L/m²·h resulted in insignificant of COD removal. Nevertheless, the UF process was able to remove up to 54% of Fe 2+ at pH in alkaline condition with 8.5. In addition, a decrease in membrane permeability down to 0.2 L/m²h/bar over time, according to the filtered specific volume during the UF process, indicates fouling of the UF membrane during the 120 minutes of filtration. While the combined approach does not show significant improvement in COD removal, it does help to reduce the chemical footprint of the process, which is an important factor for the applicability of the selected water treatment method.

Maximizing N-Nitrosamine Rejection via RO Membrane Plugging with Hexylamine and Hexamethylenediamine.

The rapid expansion of urban areas and the increasing demand for water resources necessitate substantial investments in technologies that enable the reuse of municipal wastewater for various purposes. Nonetheless, numerous challenges remain, particularly regarding disinfection by-products (DBPs), especially carcinogenic compounds such as N-nitrosamines (NTRs). To tackle the ongoing issues associated with reverse osmosis (RO) membranes, this study investigated the rejection of NTRs across a range of commercially available RO membranes. In addition, the research aimed to improve rejection rates by integrating molecular plugs into the nanopores of the polyamide (PA) layer. Hexylamine (HEX) and hexamethylenediamine (HDMA), both linear chain amines, have proven to be effective as molecular plugs for enhancing the removal of NTRs. Given the environmental and human health concerns associated with linear amines, the study also aimed to assess the feasibility of diamine molecules as potential alternatives. The application of molecular plugs led to changes in pore size distribution (PSD) and effective pore number, resulting in a decrease in membrane permeability (from 5 to 33%), while maintaining levels suitable for RO processes. HEX and HDMA exhibited a positive effect on NTR rejection with ACM1, ACM5 and BW30LE membranes. In particular, NDMA rejection, the smallest molecule of the tested NTRs, with ACM1 was improved by 65.5% and 70.6% after treatment with HEX and HDMA, respectively.

Spermidine mitigates salt stress in grapevine with alterations in physicochemical properties and nutrient composition

AbstractBackgroundPolyamines are plant growth regulators that exert a pivotal role in salt tolerance.AimsThis research focused on investigating the effect of spermidine on morphological and physicochemical characteristics and ion accumulation of two grapevine cultivars under NaCl stress.MethodsA greenhouse experiment was conducted with three factors, including two grapevine cultivars (Vitis vinifera L. cv. Bidaneh‐Sefid and cv. Siah‐Sardasht), four levels of NaCl (together with the nutrient solution, including 0 [control], 20, 40, and 80 mM), and four spermidine levels ([foliar spray], 0 [control], 0.25, 0.5, and 1 mM). The experiment was performed in a factorial trial in accordance with a randomized complete design with three replicates.ResultsVegetative growth indices, including leaf number, fresh and dry weight of shoot, and root, were decreased by NaCl treatments. The application of spermidine positively reduced the effects of NaCl on morphological characteristics. Moreover, NaCl and/or spermidine significantly (p ≤ 0.05) improved antioxidant enzyme activities associated with rising total protein accumulation. NaCl stress significantly decreased ion percentage (calcium, magnesium, phosphate, potassium, iron, and zinc) in the leaves of both cultivars. Based on the results, increasing salinity levels significantly boosted plant Na+ and Cl− percentage, along with increased membrane permeability and malondialdehyde (MDA) concentration. Interestingly, cv. Bidaneh‐Sefid leaves accumulated less Na+ and Cl− compared to the other cultivar. On the other hand, applying spermidine reduced the levels of Na+ and Cl− in both cultivars, and this reduction was associated with a decrease in membrane permeability and MDA concentration.ConclusionsThe findings confirmed the role of spermidine in reducing the negative effects of NaCl, although more investigations with different grapevine cultivars under NaCl stress are required.

Mechanistic analysis of membrane fouling by microplastics in a gravity-driven ceramic membrane reactor for roofing rainwater reuse

The presence of microplastics (MPs) in aquatic environments is a direct consequence of human activities and social development. Consequently, the removal of MPs is essential in water treatment processes, including the membrane filtration of roofing rainwater. Additionally, MPs carried by roofing rainwater pose potential risks to both the ecosystem and human health. However, the fouling behavior of MPs and their impact on the performance of gravity-driven ceramic membranes (GDCMs) remains largely unexplored. In this study, we investigated the effects of the coexisted MPs in rainwater, specifically granulate and fiber MPs, on the formation of fouling layers. We examined their physical and biological characteristics, such as components and microbial community structure. The results demonstrated a positive correlation between the formation of the biological functional layer and the diverse morphology of MPs, which led to a significant decrease in membrane permeability and exacerbated membrane fouling, while having no remarkable influence on permeate quality. Furthermore, different shapes of MPs exhibited varying characteristics: the cake layer of the granulate-MPs group exhibited superior compressibility, while the fiber-MPs group formed and matured more rapidly. MPs not only directly combined with organic matter but also induced metabolic products of microorganisms. Therefore, understanding the primary mechanisms of membrane fouling by MPs in GDCMs for roofing rainwater reuse is of utmost importance. Our study presents novel insights into the mechanisms of membrane fouling in the presence of coexisting MPs in roofing rainwater reuse and provides guidance for improving the performance of GDCMs in the presence of MPs.

Effect of Garlic Extract on the Erythrocyte as a Simple Model Cell.

Garlic is known to have diverse effects on mammalian cells, being cytotoxic, especially to cancer cells, but also protect against oxidative stress. Mammalian erythrocyte is a simple cell devoid of intracellular organelles, protein synthesis ability, and most signaling pathways. Therefore, examination of the effects of garlic on erythrocytes allows for revealing primary events in the cellular action of garlic extract. In this study, human erythrocytes or erythrocyte membranes were exposed to garlic extract at various dilutions. Hemoglobin oxidation to methemoglobin, increased binding of hemoglobin to the membrane, and formation of Heinz bodies were observed. Garlic extract depleted acid-soluble thiols, especially glutathione, and induced a prooxidative shift in the cellular glutathione redox potential. The extract increased the osmotic fragility of erythrocytes, induced hemolysis, and inhibited hemolysis in isotonic ammonium chloride, indicative of decreased membrane permeability for Cl- and increased the membrane fluidity. Fluorescent probes indicated an increased level of reactive oxygen species and induction of lipid peroxidation, but these results should be interpreted with care since the extract alone induced oxidation of the probes (dichlorodihydrofluorescein diacetate and BODIPY C11). These results demonstrate that garlic extract induces oxidative changes in the erythrocyte, first of all, thiol and hemoglobin oxidation.

Medicinal Chemistry of Drugs with N-Oxide Functionalities.

Molecules with N-oxide functionalities are omnipresent in nature and play an important role in Medicinal Chemistry. They are synthetic or biosynthetic intermediates, prodrugs, drugs, or polymers for applications in drug development and surface engineering. Typically, the N-oxide group is critical for biomedical applications of these molecules. It may provide water solubility or decrease membrane permeability or immunogenicity. In other cases, the N-oxide has a special redox reactivity which is important for drug targeting and/or cytotoxicity. Many of the underlying mechanisms have only recently been discovered, and the number of applications of N-oxides in the healthcare field is rapidly growing. This Perspective article gives a short summary of the properties of N-oxides and their synthesis. It also provides a discussion of current applications of N-oxides in the biomedical field and explains the basic molecular mechanisms responsible for their biological activity.

Soil amendments with nanoparticles control cucumber wilt caused by Fusarium oxysporium

Management of Fusarium wilt, a destructive plant disease, mainly relies on chemicals, but research on novel and eco-friendly methods is needed due to the hazardous effects of chemical pesticides. This study explored the soil application of zinc oxide nanoparticles (ZnONPs) to manage Fusarium wilt disease in cucumber plants. The antifungal activity of ZnONPs against in-vitro growth of Fusarium oxysporum was tested through food poisoning test on the potato dextrose agar medium. The in-vivo potential of NPs for managing Fusarium wilt was checked in pot experiment. In-vitro results confirmed the concentration-dependent in-vitro antifungal activity. The NPs application at 500 µg/ml and 600 µg/ml concentrations showed phytotoxicity and significantly inhibited seed germination and growth of cucumber plants. However, NPs at 300 µg/ml significantly suppressed the pathogenic effects of F. oxysporum on cucumber plants without any phytotoxic effect. The pathogen-inoculated cucumber plants grown in soil amended with NPs showed significantly enhanced growth, lower disease severity, and improved root physiology compared to untreated plants. The plants under NPs treatment showed higher chlorophyll and nitrogen content while decreased membrane permeability and malondialdehyde content. Along with direct antifungal activity, the application of NPs caused an increased expression of defense-related genes and higher activities of defense-related enzymes. These findings verified the efficiency of ZnONPs for suppressing Fusarium wilt disease in cucumber crops, thereby promoting a non-chemical and environmentally friendly approach to controlling Fusarium wilt disease.

Effects of plasticizer on removal of antibiotics and antibiotic resistance genes from agricultural soils via soil microbial fuel cells

Soil microbial fuel cells (MFCs), a novel ecosystem technology, have recently been intensively studied for antibiotic-polluted soils. However, actual agricultural soils are always contaminated by mixed pollutants, especially plasticizers from extensively used agricultural plastic films. The aim of this study is to investigate the effect of di-2-ethylhexyl phthalate (DEHP, a representative plasticizer in soil) on the removal of sulfadiazine (SDZ, a frequently detected antibiotic in natural environments), antibiotic resistance genes (ARGs), and the microbial community in soil MFCs. Our results confirmed that soil MFCs maintained a good antibiotic removal ability even under the influence of residual DEHP and achieved a higher removal performance at higher DEHP concentrations due to enhanced power generation. Specifically, a higher DEHP concentration had a favorable effect on antibiotic removal in soil MFCs because the biodegradation efficiency was improved in both the upper (i.e., to 0.268 ± 0.021 mg kg−1 from 4.867 ± 0.221 mg kg−1) and lower layers (i.e., to 0.293 ± 0.047 mg kg−1 from 4.867 ± 0.221 mg kg−1) of polluted soils. Moreover, a high DEHP concentration significantly promoted the abundance of bacteria associated with electricity generation compared with a lower DEHP concentration, resulting in the promotion of extracellular electron transfer, and enhancing SDZ degradation. The increased ARG abundance may have been caused by the enrichment of ARG potential hosts brought about by high DEHP concentrations, likely due to the increased conjugative transfer rates of the RP4 plasmid due to decreased membrane permeability and an increased reactive oxygen species content. The results revealed the ecological risk of residual DEHP in soil that promotes ARG transmission in soil MFCs, although it has the potential to reduce SDZ toxicity through horizontal gene transfer. We also highlight concerns regarding the management of antibiotics and plasticizers in soil. The negative effects of plasticizers on antibiotic removal should be carefully evaluated when using soil MFCs for the in situ remediation of antibiotic-contaminated soil.

Pseudomonas aeruginosa biofilm formation and its resistance to beta-lactam antibiotics

ABSTRACT Introduction: An opportunistic pathogen, Pseudomonas aeruginosa is a Gram-negative bacteria that causes acute and chronic human infections. By adhering to appropriate surfaces and creating a biofilm matrix, Pseudomonas aeruginosa has a high-resistance structure. Due to biofilm resistance mechanisms, this bacterial biofilm may increase natural antibiotic resistance. Antibiotics have difficulty penetrating the exopolysaccharide matrix that makes up the biofilm structure (Psl, Pe, alginate, and eDNA). Alginate is involved in generating mucus, and Psl and Pel components are implicated in biofilm development and antibiotic resistance. Due to the connection between biofilm production and antibiotic resistance, Pseudomonas aeruginosa involves mechanisms of beta-lactam antibiotic resistance. Objective: On this basis, learning more about the connection between Pseudomonas aeruginosa bacteria's ability to form biofilms and their resistance to beta-lactam antibiotics is essential. Methods: We use literature methods from various literature on the biofilm formation of P. aeruginosa and its resistance to beta-lactam antibiotics, including research papers and studies with no restrictions types of studies included in this article. Discussion: Pseudomonas aeruginosa has intrinsic and adaptive antibiotic resistance mechanisms. Decreased membrane permeability, the production of enzymes resistant to antibiotics, chromosomal changes, and horizontal gene transfer from other bacteria contribute to antimicrobial resistance. Beta-lactam antibiotic resistance mechanisms are known to be developed by Pseudomonas aeruginosa. The resistance characteristics of Pseudomonas aeruginosa may change phenotypically due to biofilm development. This article will be helpful in future research on Pseudomonas aeruginosa therapy and medication.

Discovery of a potent, orally available tricyclic derivative as a novel BRD4 inhibitor for melanoma

The epigenetic regulation of the protein bromodomain-containing protein 4 (BRD4) has emerged as a compelling target for cancer treatment. In this study, we outline the discovery of a novel BRD4 inhibitor for melanoma therapy. Our initial finding was that benzimidazole derivative 1, sourced from our library, was a powerful BRD4 inhibitor. However, it exhibited a poor pharmacokinetic (PK) profile. To address this, we conducted a scaffold-hopping procedure with derivative 1, which resulted in the creation of benzimidazolinone derivative 5. This new derivative displayed an improved PK profile. To further enhance the BRD4 inhibitory activity, we attempted to introduce hydrogen bond acceptors. This indeed improved the activity, but at the cost of decreased membrane permeability. Our search for a potent inhibitor with desirable permeability led to the development of tricyclic 18. This compound demonstrated powerful inhibitory activity and a favorable PK profile. More significantly, tricyclic 18 showed antitumor efficacy in a mouse melanoma xenograft model, suggesting that it holds potential as a therapeutic agent for melanoma treatment.

Characterization and heterologous expression of plasmalogen synthase MeHAD from Megasphaera elsdenii

Plasmalogens (Pls) are vinyl-ether bond-containing glycerophospholipids or glycosyl diradyl glycerols, and are of great importance in the physiological functions and stability of cell membrane. Here, we identified and characterized that the plasmalogen synthase MeHAD from anaerobic Megasphaera elsdenii was responsible for vinyl-ether bond formation. Different from the 2-hydroxyacyl-CoA dehydratase (HAD) family plasmalogen synthase PlsA-PlsR which are encoded by two genes in Clostridium perfringens, the HAD homolog (MeHAD) encoded by a single gene MELS_0169 was found in M. elsdenii. By heterologous expression of the MeHAD gene into a nonplasmalogen-producing Escherichia coli strain, the expressed MeHAD was found to be located in the cell membrane region. Plasmalogens were detected in the recombinant strain using GC–MS and LC-MS, demonstrating that MeHAD was the key enzyme for plasmalogen synthesis. Moreover, the synthesized plasmalogens could enhance the oxidative stress-resistance and osmotic pressure-resistance of the recombinant strain, probably due to the ROS scavenging and decreased membrane permeability by the plasmalogens, respectively. The four-cysteine (Cys125, Cys164, Cys445 and Cys484) site-mutant of MeHAD, which were predicted binding to the [4Fe-4S] cluster, was unable to synthesize plasmalogens, indicating that the cysteines are important for the catalytic activity of MeHAD. Our results revealed the single gene encoded plasmalogen synthase in M. elsdenii and established a recombinant E. coli strain with plasmalogen production potential.

Forward osmosis membrane doped with water-based zirconium fumarate MOFs to enhance dye pollutant removal and membrane antifouling performance.

Metal-organic frameworks (MOFs) can be applied to enhance the property of forward osmosis membranes. However, organic solvents can easily remain in organic synthetic metal-organic frame materials and cause membrane fouling and a decrease in membrane permeability. In this study, water-based Zr-fumarate MOFs were synthesized and doped into the membrane active layer by interfacial polymerization to provide a water-based MOF-doped thin-film composite membrane (TFC membrane). It was found that doping the water-based MOFs effectively improved membrane hydrophilicity, and nanowater passages were introduced in the active layer to improve permeability. The water flux of the water-based MOF-doped TFC membranes was increased by 21% over that of the original membrane, and the selectivity performance of the membrane was improved while keeping the salt rejection basically unchanged. Additionally, the water-based MOF-doped TFC membrane showed good removal efficiency (Rd > 94%) and strong antipollution performance in the treatment of dye pollutants.

Doping silver nanoparticles into reverse osmosis membranes for antibacterial properties

Abstract Polyamide composite reverse osmosis (RO) membranes occupy an important position in water treatment. However, membrane fouling, especially biofouling, can lead to a significant decrease in membrane permeability. Therefore, reducing biological contamination is a significant and important property of an RO membrane. In this article, a hypothesis on the development of a new kind of RO membrane for antibacterial purposes was prepared by the modification of gallic acid (GA) and silver nanoparticles (AgNPs). Then, experiments were carried out to verify the hypothesis, getting a modified RO membrane with the composite of GA@AgNPs. The water flux of the GA@AgNPs RO membrane was 31.1 L·m−2·h−1, which was 46.7% higher than that of the original membrane, while the rejection rate of salt remained at 93.8–97.6%. Moreover, the GA@AgNPs RO membranes exhibited outstanding antibacterial properties with more than 99.9% antibacterial efficiency against both Escherichia coli and Staphylococcus aureus. Our work provides a new idea for solving the problem of biofouling RO membranes.

Nonlinear Transient Permeability in pH-Responsive Bicontinuous Nanospheres

We demonstrate the construction of pH-responsive bicontinuous nanospheres (BCNs) with nonlinear transient permeability and catalytic activity. The BCNs were assembled from amphiphilic block copolymers comprising pH-responsive groups and were loaded with the enzymes urease and horseradish peroxidase (HRP). A transient membrane permeability switch was introduced by employing the well-known pH-increasing effect of urease upon conversion of urea to ammonia. As expected, the coencapsulated HRP displayed a transiently regulated catalytic output profile upon addition of urea, with no significant product formation after the pH increase. This transient process displayed a nonlinear "dampening" behavior, induced by a decrease in membrane permeability as a result of significant local ammonia production. Furthermore, the catalytic output of HRP could be modulated by addition of different amounts of urea or by altering the buffer capacity of the system. Finally, this nonlinear dampening effect was not observed in spherical polymersomes, even though the membrane permeability could also be inhibited by addition of urea. The specific BCN morphology therefore allows to optimally control catalytic processes by pH changes in the nanoreactor microenvironment compared to bulk conditions due to its unique permeability profile.

Effect of the Addition of Polyacrylic Acid of Different Molecular Weights to Coagulation Bath on the Structure and Performance of Polysulfone Ultrafiltration Membranes

Membrane fouling is a serious issue in membrane technology which cannot be completely avoided but can be diminished. The perspective technique of membrane modification is the introduction of hydrophilic polymers or polyelectrolytes into the coagulation bath during membrane preparation via non-solvent-induced phase separation. The influence of polyacrylic acid (PAA) molecular weight (100,000, 250,000 and 450,000 g·mol-1) added to the aqueous coagulation bath (0.4-2.0 wt.%) on the polysulfone membrane structure, surface roughness, water contact angle and zeta potential of the selective layer, as well as the separation and antifouling performance, was systematically studied. It was found that membranes obtained via the addition of PAA with higher molecular weight feature smaller pore size and porosity, extremely high hydrophilicity and higher values of negative charge of membrane surface. It was shown that the increase in PAA concentration from 0.4 wt.% to 2.0 wt.% for all studied PAA molecular weights yielded a substantial decrease in water contact angle compared with the reference membrane (65 ± 2°) (from 27 ± 2° to 17 ± 2° for PAA with Mn = 100,000 g·mol-1; from 25 ± 2° to 16 ± 2° for PAA with Mn = 250,000 g·mol-1; and from 19 ± 2° to 10 ± 2° for PAA with Mn = 450,000 g·mol-1). An increase in PAA molecular weight from 100,000 to 450,000 g·mol-1 led to a decrease in membrane permeability, an increase in rejection and tailoring excellent antifouling performance in the ultrafiltration of humic acid solutions. The fouling recovery ratio increased from 73% for the reference membrane up to 91%, 100% and 136% for membranes modified with the addition to the coagulation bath of 1.5 wt.% of PAA with molecular weights of 100,000 g·mol-1, 250,000 g·mol-1 and 450,000 g·mol-1, respectively. Overall, the addition of PAA of different molecular weights to the coagulation bath is an efficient tool to adjust membrane separation and antifouling properties for different separation tasks.

Assessing anti-transpiration potential of beeswax waste on Calendula officinalis under drought stress conditions

Beeswax waste, as a novel biostimulant, may be involved in anti-transpiration process in plants exposed to drought stress. Therefore, the aim of this study was to investigate the anti-transpiration effect of beeswax waste in comparison with chitosan, a known anti-transpiration substance. The treatments consisted of two drought stress conditions [no stress, 90% field capacity; and stress, 40% field capacity (FC)] together with four exogenous foliar applications [control (water), beeswax waste extract (BWE), chitosan, and BWE +chitosan]. Plants subjected to irrigation with 40% FC displayed a significant reduction in plant yield and physiological traits. In drought stress, foliar application with BWE and BWE + chitosan increased shoot dry weight, flower number and weight, net photosynthesis (Pn), essential oil percentage and yield, and decreased membrane permeability compared with water and chitosan spraying. Under drought stress, foliar treatment with BWE and chitosan decreased stomatal conductivity by about 8% and 31%, and transpiration (Tr) by 7% and 22%, respectively compared with water spraying. Under these conditions, the leaves sprayed with BWE and BWE + chitosan exhibited a lower temperature compared with water and chitosan treatments. Furthermore, foliar spraying with BWE + chitosan, BWE and chitosan increased the water use efficiency (WUE) by 104%, 92% and 56%, respectively, compared to control. Foliar application with BWE, chitosan and BWE + chitosan improved ascorbate peroxidase (APX) and catalase (CAT) activity and osmoregulation parameters (increased proline, proteins and soluble sugars) as plant adaptive mechanisms to drought. In conclusion, BWE can mitigate the drought stress similarly to chitosan, a better known anti-transpiration agent.

Interplay between membrane imperfections and external concentration polarization

Reverse osmosis membranes provide a highly effective and efficient barrier against various kinds of pollutants. Their reliability depends on the integrity of the active layer: in case the active layer is damaged and contains imperfections, unfiltered feed solution can contaminate the permeate. Various types of integrity monitoring techniques have been developed to verify membrane performance, of which the rejection of fluorescent dyes is a well-established technique. Fluorescent dyes are however relatively small solutes for which the membranes can display non-zero diffusive permeability, such that not all dye passage can be attributed to membrane imperfections. Additionally, fluorescent dyes are subject to external concentration polarization (ECP) during filtration, causing a flux-dependent enrichment at the membrane surface, further complicating the analysis of dye rejection data. This study presents a model to discern between membrane permeability, enrichment by ECP and passage through imperfections. The consequences of imperfections on solute passage are explored, showing that imperfections only contribute significantly to the passage of solutes with a low membrane permeability. This leads to underestimates of the external mass transfer coefficient, with the error being increasingly large with decreasing membrane permeability coefficient, relative to the case of an imperfection-free membrane. This error is then related to the proportionality of the Sherwood number, used to calculate external mass transfer coefficients, with solute diffusivity, allowing the quantification of the contribution of imperfections to water flux. The model was experimentally verified using Pyranine rejection in two membrane types, both operated in a lab-scale flat sheet crossflow test system, finding proof of imperfections in one membrane type.

Role of AlgC and GalU in the Intrinsic Antibiotic Resistance of Helicobacter pylori.

Helicobacter pylori is associated with the development of gastrointestinal diseases. However, its eradication is challenged by an increased rate of drug resistance. AlgC and GalU are important for the synthesis of UDP-glucose, which is a substrate for the synthesis of lipopolysaccharide (LPS) in H. pylori. In this study, we investigated the role of UDP-glucose in the intrinsic drug resistance in H. pylori. Gene knockout strains or complementation strains, including ΔalgC, ΔgalU, ΔgalE, Δhp0045, ΔalgC/algC* and ΔgalU/galU* were constructed in Hp26695; and ΔalgC and ΔgalU were also constructed in two clinical drug-resistant strains, Hp008 and Hp135. The minimum inhibitory concentrations (MIC) of H. pylori to amoxicillin (AMO), tetracycline (TET), clarithromycin (CLA), metronidazole (MNZ), levofloxacin (LEV), and rifampicin (RIF) were measured using MIC Test Strips. Silver staining was performed to examine the role of AlgC and GalU in LPS synthesis. Ethidium bromide (EB) accumulation assay was performed to assess the outer membrane permeability of H. pylori strains. Knockout of algC and galU in H. pylori resulted in increased drug sensitivity to AMO, MNZ, CLA, LEV, and RIF; whereas knockout of hp0045 and galE, which are involved in GDP-fucose and UDP-galactose synthesis, respectively, did not significantly alter the drug sensitivity of H. pylori. Knockout of algC and galU in clinically drug-resistant strains resulted in significantly increased drug sensitivity to all the antibiotics, except MNZ. The lipid A-core structure was altered in ΔalgC and ΔgalU when their EB accumulation was higher than that in the wild type and complementation strains. UDP-glucose may play an important role in increasing drug resistance to AMO, MNZ, CLA, LEV, TET, and RIF by maintaining the lipid A-core structure and decreasing membrane permeability. AlgC and GalU may serve as potential drug targets for decreasing antibiotic resistance in clinical isolates.

Effect of OH-Group Introduction on Gas and Liquid Separation Properties of Polydecylmethylsiloxane.

Membrane development for specific separation tasks is a current and important topic. In this work, the influence of OH-groups introduced in polydecylmethylsiloxane (PDecMS) was shown on the separation of CO2 from air and aldehydes from hydroformylation reaction media. OH-groups were introduced to PDecMS during hydrosilylation reaction by adding 1-decene with undecenol-1 to polymethylhydrosiloxane, and further cross-linking. Flat sheet composite membranes were developed based on these polymers. For obtained membranes, transport and separation properties were studied for individual gases (CO2, N2, O2) and liquids (1-hexene, 1-heptene, 1-octene, 1-nonene, heptanal and decanal). Sorption measurements were carried out for an explanation of difference in transport properties. The general trend was a decrease in membrane permeability with the introduction of OH groups. The presence of OH groups in the siloxane led to a significant increase in the selectivity of permeability with respect to acidic components. For example, on comparing PDecMS and OH-PDecMS (~7% OH-groups to decyl), it was shown that selectivity heptanal/1-hexene increased eight times.

The development of variation-based rifampicin resistance in Staphylococcus aureus deciphered through genomic and transcriptomic study.

Rifampicin (RIF) resistance imposes a challenge on the antimicrobial treatment of pathogen infections. Figuring out the development mechanism of RIF resistance is critical to improving antimicrobial therapy strategy in clinics and biological treatment strategy of RIF polluted sewage in environmental engineering. The RIF resistance development of Staphylococcus aureus (S. aureus) with exposure to RIF at sub-inhibitory concentrations was comprehensively investigated via genomic and transcriptomic approaches in this study. RIF minimal inhibitory concentration (MIC) for S. aureus rapidly increased from 0.032 to 256mg/L. Membrane permeability decrease, biofilm formation enhancement, and ROS production increase associated with RIF resistance were observed in RIF-induced strains. Through comparative genomic analysis, mutations in rpoB and rpoC were considered to be associated with RIF resistance in S. aureus mutants. Pan-genome-wide single-nucleotide variant analysis indicated that mutations at rpoB-1412, rpoB-1451, and rpoB-1457 were prevalent in 13849 public genomes of S. aureus, while mutations at rpoB-2256, and rpoC-3092 were first discovered in this study. The panorama of adaptative alteration of cellular physiological processes was observed via transcriptomic analysis. The oxidation pressure responses, metabolism, transporters, virulence factors, and multiple steps of DNA and RNA machinery were found to be perturbed by RIF in S. aureus.