Destruction Of Cell Membrane Research Articles

Cytosporone B as a Biological Preservative: Purification, Fungicidal Activity and Mechanism of Action against Geotrichum citri-aurantii.

To prevent citrus decay caused by Geotrichum citri-aurantii, 12 natural products were isolated from two endophytic fungi, in which cytosporone B was shown to have excellent bioactivity for control of G. citri-aurantii with median effect concentration (EC50) of 26.11 μg/mL and minimum inhibitory concentration (MIC) of 105 μg/mL, and also significantly reduced the decay of sugar orange during the in vivo trials. In addition, cytosporone B could alter the morphology of G. citri-aurantii by causing distortion of the mycelia and loss of membrane integrity. Differentially expressed genes (DEGs) between cytosporone B-treated and -untreated samples were revealed by Illumina sequencing, including 3540 unigenes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that most DEGs were related to metabolic production and cell membrane. These findings suggest cytosporone B is a promising biological preservative to control citrus decay and reveal the action mechanism of cytosporone B in relation to the destruction of the fungal cell membrane at both morphological and molecular levels.

Increased Resistance of Salmonella enterica Serovar Typhimurium and Escherichia coli O157:H7 to 222-Nanometer Krypton-Chlorine Excilamp Treatment by Acid Adaptation.

In this study, we examined the change in resistance of Salmonella enterica serovar Typhimurium and Escherichia coli O157:H7 to 222-nm krypton-chlorine (KrCl) excilamp treatment as influenced by acid adaptation and identified a mechanism of resistance change. In addition, we measured changes in apple juice quality indicators, such as color, total phenols, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity, during treatment. Non-acid-adapted and acid-adapted pathogens were induced by growing the cells in tryptic soy broth without dextrose (TSB w/o D) at pH 7.3 and in TSB w/o D at pH 5.0 (adjusted with HCl), respectively. For the KrCl excilamp treatment, acid-adapted pathogens exhibited significantly (P < 0.05) higher D5d values, which indicate dosages required to achieve a 5-log reduction, than those for non-acid-adapted pathogens in both commercially clarified apple juice and phosphate-buffered saline (PBS), and the pathogens in the juice showed significantly (P < 0.05) higher D5d values than those for pathogens in PBS because of the UV-absorbing characteristics of apple juice. Through mechanism identification, it was found that the generation of lipid peroxidation in the cell membrane, inducing cell membrane destruction, was significantly (P < 0.05) lower in acid-adapted cells than in non-acid-adapted cells for the same amount of reactive oxygen species (ROS) generated at the same dose because the ratio of unsaturated to saturated fatty acids (USFA/SFA) in the cell membrane was significantly (P < 0.05) decreased as a result of acid adaptation. Treated apple juice showed no significant (P > 0.05) difference in quality indicators compared to those of untreated controls during treatment at 1,773 mJ/cm2IMPORTANCE There is a need for novel, mercury-free UV lamp technology to replace germicidal lamps containing harmful mercury, which are routinely utilized for UV pasteurization of apple juice. In addition, consideration of the changes in response to antimicrobial treatments that may occur when pathogens are adapted to the acid in an apple juice matrix is critical to the practical application of this technology. Based on this, an investigation using 222-nm KrCl excilamp technology, an attractive alternative to mercury lamps, was conducted. Our study demonstrated increased resistance to 222-nm KrCl excilamp treatment as pathogens adapted to acids, and this was due to changes in reactivity to ROS with changes in the fatty acid composition of the cell membrane. Despite increased resistance, the 222-nm KrCl excilamp achieved pathogen reductions of 5 log or more at laboratory scale without affecting apple juice quality. These results provide valuable baseline data for application of 222-nm KrCl excilamps in the apple juice industry.

Antifungal activity and mechanism of citral, limonene and eugenol against Zygosaccharomyces rouxii

The aim of this study was to investigate the antifungal activity and mechanisms of citral, limonene and eugenol against Zygosaccharomyces rouxii. All the three essential oil ingredients presented strong antifungal activities against Z. rouxii. Minimum inhibitory concentrations of citral, limonene and eugenol were 0.188, 0.75 and 0.4 μL/mL, and the minimum fungicidal concentrations were 0.375, 3 and 0.8 μL/mL, respectively. Scanning electron microscopy showed that the tested essential oil compounds had destructive effects on the yeast cell surface. After treated by citral, limonene and eugenol, the relative electric conductivity and leakage of nucleic acid were increased significantly. SDS-PAGE analysis indicated that the essential oil components could result in the loss of soluble proteins and might also destroy the yeast protein or inhibit their expression. These results demonstrated that citral, limonene and eugenol exerted their antifungal action against Z. rouxii through cell membrane damage and destruction of cellular proteins. This study provided a theoretical possibility that citral, limonene and eugenol could be used as natural food preservatives for the control of Z. rouxii-related spoilage in the fruit juice industry.

Conformational-transited protein corona regulated cell-membrane penetration and induced cytotoxicity of ultrasmall Au nanoparticles.

Nanoparticles (NP) in biological fluids almost invariably become coated with proteins to form protein coronas. It is the NP–protein corona rather than the bare nanoparticle that determines the nanoparticle's bio-behavior. Here, ultrasmall gold nanoparticles (AuNPs) coated by a human serum albumin (HSA) corona were studied by Fourier transform infrared spectroscopy, denature experiments, fluorescence quenching. Moreover, the intracellular fate of AuNPs and the AuNP–HSA corona has also been investigated. The results show that HSA corona undergo a conformational transition (partial β-sheet changed to α-helicity) when they adsorb on AuNPs, which lead to an enhanced thermal stability. Importantly, we observed that the conformation-transited protein corona–AuNP complex could induce cell apoptosis. Meanwhile, for the first time, the conformation-transited HSA on the AuNPs surface are shown to disrupt living cell membranes. The results obtained here not only provide the detailed conformational behavior of HSA molecules on nanoparticles, but also reveal the structure–function relationship of protein corona, which is of utmost importance in the safe application of nanoscale objects in living organisms.

Epidural Anesthesia for Caesarean Section in a Patient with Risk of Malignant Hyperthermia

Abstract Malignant hyperthermia is a hypermetabolic disorder of skeletal muscle that occurs in genetically susceptible individuals after exposure to anesthetic. Basic disorder is an increase of calcium ions inside the skeletal muscle, increasing metabolism and reducing cell energy supplies leading to development of acidosis, cell membrane destruction and cell death. Due to the increased metabolism occurs hypercarbia and strong stimulation of the sympathetic nervous system (tachycardia, hypertension, ventricular arrhythmia, tachypnea dropped for the neuromuscular blockade). Sweating, cyanosis, muscle rigidity and hyperthermia are also present. This work presents the case of a female patient aged 32 who was heterozygous for the mutation RYR1 gene and therefore has an increased risk of malignant hyperthermia. Per anamnesis we got data that patient’s brother suffers from central core disease (myopathy). Patient has no muscle disease, 41st week of pregnancy and was admitted to the hospital for childbirth. Vaginal delivery in epidural analgesia was planned. Epidural catheter is placed in the space L3 - L4, through which she received 0.25% levobupivacaine 10 ml. Due to adverse obstetric findings cesarean section underwent after two hours. Given the increased risk of malignant hyperthermia, the safest type of anesthesia for cesarean is epidural anesthesia. Over the epidural catheter has received 0.5% levobupivacaine 18 ml. Anesthesia machine was verified, hoses were replaced with new ones, CO2 absorber system was replaced, and whole system is flushed with pure oxygen, before surgery started. During the operation the patient had stable vital parameters that are monitored. She got a male child Apgar score of 9/10 and saw her child at birth. After the operation was transferred to the intensive care unit where we monitored the vital parameters, laboratory analysis, the amount and color of urine. Since all parameters were satisfactory, following day she was transferred to the ward, and she was discharged with a child on the fourth day after the surgery.

Study of cancer cells response row K562 to Low-Dose- Beta irradiation and determination of absorbed dose using Monte Carlo method

Introduction: Cancer is, in essence, a genetic disease and is the second leading cause of death globally. Fortunately, many common types of cancer are treatable if detected early and of course there are many medications and treatments available today. Among the new methods to treat cancer, radiotherapy seems to be hopeful in patients with malignancies. This work investigates the strontium beta irradiation (90Sr) dose response on the clonogenicity of Animal blood cancer cell row K562. Scope of this work is the survey of cells survival for three time periods of irradiations and calculating absorbed doses of cancer cells by Monte Carlo simulation. Materials and Methods: The K562 cells were cultured and irradiated with β-particle emitted from 90Sr, daily 30 minutes, 1 hour and 2 hours for 3 days. Cells survival was evaluated by three methods of MTT assay, cell visual survey and DNA electrophoresis after irradiation. To compare the results of cells survival after irradiation, determination of absorbed dose of cancer cells is necessary. But, the short ranges of the emitted beta particles and the associated large dose gradients make experimental measurements particularly difficult. In this circumstance, we have motivated by using of Monte Carlo simulation techniques. To calculate absorbed doses of cancer cells via Monte Carlo, the problem was simulated with MCNP code. Of course, to verify results of simulation with results experimental, we used a Geiger Muller counter and estimated a Scaling Factor. Results: cell visual survey presents photomicrographs of blood cancer cells sections indicating the number of the survive cells after irradiations. Survival percent were obtained for three time periods of irradiations in MTT assay. The survival of cells was described as a function of dose and these absorbed doses were determined using MCNPX code. Finally, to recognize that The cells death was been only due to the destruction of the cell membrane, or the irradiation affect DNA and break it, we did DNA electrophoresis assay. Conclusion: Cell visual survey indicates the positive effectiveness of beta particles on cancer cells. Also, Comparing the survival curves, that hypersensitivity component and dose rate effects are small or absent in high LET, we estimated α component. Eventually, checking the DNA electrophoresis, we understood that in very low-dose- rate up to 2.213±0.0015cGy, cells death Arises from destructing the cell membrane but form 2.213±0.0015 cGy to top, ray begin to effect on DNA.

Hydroxytyrosol (HT) Analogs Act as Potent Antifungals by Direct Disruption of the Fungal Cell Membrane.

Fungal infections constitute an emerging threat and a prevalent health problem due to increasing number of immunocompromised people and pharmacological or other treatments aiming at viral infections, cancer or allergies. Currently used antifungals suffer from inefficiency, toxic side effects and developing drug-resistance. Additionally, over the last two decades no new classes of antifungals have been approved, emphasizing the urgent need for developing a novel generation of antifungals. Here, we investigate the antifungal activity of a series of chemically synthesized Hydroxytyrosol (HT) analogs. HT is one of the major phenolic compounds in olive oil, shown to possess radical-scavenging antioxidant, antiproliferative, proapoptotic and anti-inflammatory activities. No previous report has studied HT analogs as antifungals. We show that specific analogs have broad and strong antifungal activity, significantly stronger than the parent compound HT. Using Aspergillus nidulans as an in vivo cellular model system, we show that antifungal HT analogs have an unprecedented efficiency in fungal plasma membrane destruction. Importantly, antifungal HT analogs did not show toxicity in a mammalian cell line, whereas no resistance to HT analogs was obtained by standard mutagenesis. Our results open the way for the development of a novel, efficient and safer class of antifungals.

Detection and Inhibition of Bacteria on a Dual-Functional Silver Platform.

Detection and inhibition of bacteria are universally required in clinics and daily life for health care. Developing a dual-functional material is challenging and in demand, engaging advanced applications for both defined bioanalysis and targeted biotoxicity. Herein, magnetic silver nanoshells are designed as a multifunctional platform for the detection and inhibition of bacteria. The optimized magnetic silver nanoshells enable direct laser desorption/ionization mass spectrometry based metabolic analysis of bacteria (≈10 µL-1 ), in complex biofluids. The serum infection process (0-10 h) is monitored by statistics toward clinical classification. Moreover, magnetic silver nanoshells facilitate surface adhesion on bacteria due to nanoscale surface roughness and thus display long-term antibacterial effects. Bacteria metabolism is studied with metabolic biomarkers (e.g., malate and lysine) identified during inhibition, showing cell membrane destruction and dysfunctional protein synthesis mechanisms. This work not only guides the design of material-based approaches for bioanalysis and biotoxicity, but contributes to bacteria-related diagnosis by using specific metabolic biomarkers for sensitive detection and new insights by monitoring metabolomic change of bacteria for antibacterial applications.

Activity of Thioallyl Compounds From Garlic Against Giardia duodenalis Trophozoites and in Experimental Giardiasis.

Fresh aqueous extracts (AGEs) and several thioallyl compounds (TACs) from garlic have an important antimicrobial activity that likely involves their interaction with exposed thiol groups at single aminoacids or target proteins. Since these groups are present in Giardia duodenalis trophozoites, in this work we evaluated the anti-giardial activity of AGE and several garlic's TACs. In vitro susceptibility assays showed that AGE affected trophozoite viability initially by a mechanism impairing cell integrity and oxidoreductase activities while diesterase activities were abrogated at higher AGE concentrations. The giardicidal activities of seven TACs were related to the molecular descriptor HOMO (Highest Occupied Molecular Orbital) energy and with their capacity to modify the –SH groups exposed in giardial proteins. Interestingly, the activity of several cysteine proteases in trophozoite lysates was inhibited by representative TACs as well as the cytopathic effect of the virulence factor giardipain-1. Of these, allicin showed the highest anti-giardial activity, the lower HOMO value, the highest thiol-modifying activity and the greatest inhibition of cysteine proteases. Allicin had a cytolytic mechanism in trophozoites with subsequent impairment of diesterase and oxidoreductase activities in a similar way to AGE. In addition, by electron microscopy a marked destruction of plasma membrane and endomembranes was observed in allicin-treated trophozoites while cytoskeletal elements were not affected. In further flow cytometry analyses pro-apoptotic effects of allicin concomitant to partial cell cycle arrest at G2 phase with the absence of oxidative stress were observed. In experimental infections of gerbils, the intragastric administration of AGE or allicin decreased parasite numbers and eliminated trophozoites in experimentally infected animals, respectively. These data suggest a potential use of TACs from garlic against G. duodenalis and in the treatment of giardiasis along with their additional benefits in the host's health.

Systematic Assessment of the Toxicity and Potential Mechanism of Graphene Derivatives In Vitro and In Vivo.

Graphene is a two-dimensional crystal that is stripped from pristine graphite and made of single layer of carbon atoms. Containing numerous functional groups, graphene derivatives (GDs) could be easily modified and have aroused great attention for potential applications in biomedicine. However, pristine graphene and graphene oxide (GO) could arouse cell and animal toxicity. To screen GDs with high biocompatibility applied for biomedicine, general comparison was performed about the toxicities of six GDs with diverse types of surface modification, size, and redox state, including GO, reduced GO (rGO), graphene quantum dot (GQD), aminated GQD (GQD-NH2), carboxyl GQD (GQD-COOH), and graphene oxide quantum dot (GOQD). In contrast, it was found that large particle size, oxidation state, high concentration, and long exposure time were unfavorable factors affecting the cell viability. We further explored the mechanism of different toxicity, which could be contribute to cell membrane destruction by sharpened edges of GDs (LDH release, hemolysis), ROS production, immuno-inflammatory responses, and activation of apoptotic pathways (IKK/IκBα/NF-κB and BAX/BCL-2). Overall, our combined data primarily explored the related biochemical and molecular mechanism underlying the biological behaviors and toxicity of GDs, and we also identified GQD, GQD-NH2, GQD-COOH, and GOQD could be safely used for biomedical application as drug carriers.

Application and Simplification of Cell-Based Equivalent Circuit Model Analysis of Electrical Impedance for Assessment of Drop Shock Bruising in Japanese Pear Tissues

This study was conducted with the objective of applying cell-based electrical equivalent circuit analysis for the assessment of bruising of tissues in Japanese pears after drop tests, as well as to simplify the analysis. The equivalent circuit analysis of electrical impedance values was conducted on the bruised regions of the pear tissues. The analysis showed that the resistance of the protoplasm of the injured tissues slightly increases, and the capacitance of cell membranes and the resistance of apoplastic fluids significantly decrease. Thus, it was theorized that these parameters are influenced by cell membrane destruction. Further, it was found that Cole-Cole plot parameter obtained from the frequency characteristics of the impedance of the tissues can express changes in the apoplastic fluid resistance. These results show that equivalent circuit analysis can be used to assess bruising of pear cells caused by drop shock, and the analysis can be simplified using Cole-Cole plots. We expect these results to aid in the development of physical damage assessment methods for distributed fruits.

Discovery of β-Carboline Oxadiazole Derivatives as Fungicidal Agents against Rice Sheath Blight.

A series of β-carboline oxadiazoles were synthesized, and their fungicidal activities and mechanism of action against rice sheath blight caused by Rhizoctonia solani was evaluated. The results showed that all of these compounds exhibited significant in vitro fungicidal activity. Significantly, compound 5i (EC50 = 4.2 μg/mL) displayed the best efficacy and superior fungicidal activity compared to validamycin A (EC50 = 197.6 μg/mL). Moreover, the in vivo test also demonstrated that compound 5i could effectively control rice sheath blight and showed higher in vivo protective and curative activities against R. solani than validamycin A. Preliminary mechanism studies revealed that compound 5i caused the loss of mitochondrial membrane potential, reactive oxygen species accumulation, cell membrane destruction, and DNA synthesis interference. These findings indicated that compound 5i displayed superior fungicidal activities against R. solani and could be a potential fungicidal candidate against rice sheath blight.

Inhibitory effect and mechanism of linoleic acid sustained-release microspheres on Microcystis aeruginosa at different growth phases

Environment-friendly algaecides based on allelopathy have been extensively studied to control harmful algal blooms (HABs). The inhibitory effects of linoleic acid (LA) sustained-release microspheres on different cell densities of Microcystis aeruginosa (M. aeruginosa) at different growth phases were studied. The results showed that the growth of M. aeruginosa could be inhibited within 4 days and the constant inhibitory rate with initial algal density of 8 × 105 cells∙mL−1 (exponential phase) was up to 96% compared with control. The chlorophyll-a content in the treatment group had the same change trend with the algal density and declined significantly at day 20th, which suggested that the microspheres could promote the degradation of chlorophyll-a. The activities of superoxide dismutase (SOD) and catalase (CAT) increased gradually within 5 days but then declined sharply, which indicated that LA microspheres could cause oxidative damage to M. aeruginosa during the process of inhibition and reduce the activities of antioxidant enzymes. In addition, the concentration of oxygen free radical (O2−) increased at day 10th and rose constantly, and the content of malodialdehyde (MDA) increased to 2.7 times as much as control at day 20th. Furthermore, the content of protein, nucleic acid and the conductivity in culture solution showed a significant rise. These results showed that algal cell membrane lipid peroxidation occurred and the membrane permeability increased, accompanied by the damage of cell membrane. To sum up, the destruction of algal cell membrane is the main mechanism of LA microspheres inhibiting algal growth.

Inactivation of two Mycobacteria by free chlorine: Effectiveness, influencing factors, and mechanisms

Chlorination is one of the most widely used disinfection techniques, and the problem of “chlorine-resistant bacteria” (CRB) has attracted more attention recently. In this study, the deactivation of typical CRB in water, Mycobacterium fortuitum (M. fortuitum) and Mycobacterium mucogenicum (M. mucogenicum), by free chlorine was investigated with Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) as the reference. The chlorination effectiveness of chlorine on M. fortuitum and M. mucogenicum and the effect of chlorine concentration, pH, and humic acid were studied. It was found that M. mucogenicum was more resistant to chlorine than M. fortuitum, both of which were much more resistant than E. coli and B. subtilis. The effect of disinfectant concentration on the inactivation efficiency was positive, whereas the influence of pH and humic acid was negative. The inactivation mechanisms were explored by analyzing the bacteria morphology, the destruction of cell membrane, the cell hydrophobicity, as well as total adenosine triphosphate (ATP), superoxide dismutase (SOD) activity. The slight destruction of the cell membrane was observed after deactivation with chlorine, and high hydrophobicity of the cell membrane combined with metabolic changes might lead to the chlorine tolerance of Mycobacteria.

Mercaptopyrimidine-Conjugated Gold Nanoclusters as Nanoantibiotics for Combating Multidrug-Resistant Superbugs.

Widespread bacterial resistance induced by the abuse of antibiotics eagerly needs the exploitation of novel antimicrobial agents and strategies. Gold nanoclusters (Au NCs) have recently emerged as an innovative nanomedicine, but study on their antibacterial properties especially toward multidrug resistant (MDR) bacteria is scarce. Herein, we demonstrate that a novel class of Au NCs, mercaptopyrimidine conjugated Au NCs, can act as potent nanoantibiotics targeting these intractable superbugs in vitro and in vivo, without induction of bacterial antibiotic resistance and noticeable cytotoxicity to mammalian cells. The Au NCs kill these superbugs through a combined mechanism including cell membrane destruction, DNA damage, and reactive oxygen species (ROS) generation, and exhibit excellent treatment effects in both macrophages and animal infection models induced by methicillin-resistant Staphylococcus aureus as representative. Moreover, the induction of intracellular ROS production in bacterial cells mainly attributed to the Au NCs' intrinsic oxidase- and peroxidase-like catalytic activities has been demonstrated for the first time.

Inactivation of Salmonella Typhimurium and Listeria monocytogenes on ham with nonthermal atmospheric pressure plasma.

The application of cold atmospheric pressure plasma (CAP) for decontamination of sliced ready-to-eat (RTE) meat products (in this case, rolled fillets of ham), inoculated with Salmonella (S.) Typhimurium and Listeria (L.) monocytogenes was investigated. Cold atmospheric plasma (CAP) is an ionised gas that includes highly reactive species and ozone, interacting with cell membranes and DNA of bacteria. The mode of action of CAPs includes penetration and disruption of the outer cell membrane or intracellular destruction of DNA located in the cytoplasm. Inoculated ham was treated for 10 and 20 min with CAP generated by a surface-micro-discharge-plasma source using cost-effective ambient air as working gas with different humidity levels of 45–50 and 90%. The chosen plasma modes had a peak-to-peak voltage of 6.4 or 10 kV and a frequency of 2 and 10 kHz. Under the tested conditions, the direct effectiveness of CAP on microbial inactivation was limited. Although all treated samples showed significant reductions in the microbial load subsequent to plasma treatment, the maximum inactivation of S. Typhimurium was 1.14 lg steps after 20 min of CAP-treatment (p<0.05), and L. monocytogenes was reduced by 1.02 lg steps (p<0.05) using high peak-to-peak voltage of 10 kV and a frequency of 2 kHz regardless of moisture content. However, effective inactivation was achieved by a combination of CAP-treatment and cold storage at 8°C ± 0.5°C for 7 and 14 days after packaging under sealed high nitrogen gas flush (70% N2, 30% CO2). Synergistic effects of CAP and cold storage for 14 days led to a clearer decrease in the microbial load of 1.84 lg steps for S. Typhimurium (p<0.05) and 2.55 lg steps for L. monocytogenes (p<0.05). In the case of L. monocytogenes, subsequent to CAP-treatment (10 kV, 2 kHz) and cold storage, microbial counts were predominantly below the detection limit. Measurement showed that after CAP-treatment, surface temperature of ham did not exceed the room temperature of 22°C ± 2°C. With the application of humidity levels of 45–50%, the colour distance ΔE increased in CAP treated samples due to a decrease in L* values. In conclusion, effectiveness of CAP-treatment was limited. However, the combination of CAP-treatment and cold storage of samples under modified-atmospheric-conditions up to 14 days could significantly reduce microorganisms on RTE ham. Further investigations are required to improve effectiveness of CAP-treatment.

Regulation of phytosterol biosynthetic pathway during drought stress in rice

Plants respond to drought stress in the form of various physio-biochemical and molecular changes at both cellular and molecular levels. Drought stress causes the destruction of cell membranes by disintegration of membrane lipids. One of the major groups of membrane lipids that plays important role in preserving the integrity of cell membranes is phytosterols. HMG-CoA reductase (HMGR) is the principal enzyme in the biosynthesis of plant sterols, synthesized via mevalonic acid pathway. Phospholipid: sterol acyltransferase (PSAT) is another important enzyme that plays an important role in turnover of phytosterols into steryl esters and helps maintain homeostasis of membrane lipids. In this study, the expression of both HMGR and PSAT genes in drought sensitive (IR64) and drought tolerant (N22) rice cultivars under applied drought conditions were found to be elevated. The increase in expression of these genes was proportional to the level of severity of applied drought stress. This is substantiated by the negative correlation of HMGR and PSAT expression to relative water content (RWC) and membrane stability index (MSI). Expression of PSAT was also found to be positively correlated to ABA content and HMGR expression.

Chitosan and Pichia membranaefaciens control anthracnose by maintaining cell structural integrity of citrus fruit

This work evaluated effects of chitosan and Pichia membranaefaciens treatments on anthracnose control of cell membrane and cell wall structure in citrus fruit (Citrus sinensis L. Osbeck). Pathogen infection can cause cell membrane destruction and cell wall degradation. The disease incidence and lesion diameter on chitosan- and P. membranaefaciens- treated citrus was significantly reduced, especially P. membranaefaciens. Moreover, those treatments all could regulate reactive oxygen species (ROS) to induce defense system, control the cell membrane damage, increase phenylalanine ammonia-lyase (PAL) activity to accumulate lignin, reduce cell wall related enzymes activities (PG, PME, CEL) to maintain the cell wall related compounds (pectin, cellulose) to maintain cellular integrity. These results indicated that chitosan and P. membranaefaciens treatments can control Colletotrichum gloeosporioides in citrus fruit via the maintenance of host cell structure integrity.

Biotoxicity assessment and toxicity mechanism on coal gasification wastewater (CGW): A comparative analysis of effluent from different treatment processes

Even though coal gasification wastewater (CGW) treated by various biochemical treatment processes generally met the national discharge standard, its potential biotoxicity was still unknown. Therefore, in this study, bioassay with Tetrahymena thermophila (T. thermophila) was conducted to comprehensively evaluate the variation of biotoxicity in raw CGW and the treated effluent from lab-scale micro-electrolysis integrated with biological reactor (MEBR), single iron-carbon micro-electrolysis (ICME) and conventional activated sludge (CAS) processes. The results illustrated that raw CGW presented intensive acute toxicity with 24 h EC50 value of 8.401% and toxic unit (TU) value of 11.90. Moreover, it performed significant cell membrane destruction and DNA damage even at 10% dilution concentration. The toxicant identification results revealed that multiple toxic polar compounds such as phenolic, heterocyclic and polycyclic aromatic compounds were the main contributors for biotoxicity. Furthermore, these compounds could accelerate oxidative stress, thereby inducing oxidative damage of cell membrane and DNA. As for treated effluent, TU value was decreased by 90.58% in MEBR process. An effective biotoxicity reduction was achieved in MEBR process owing to high removal efficiency in polar organic toxicants. In contrast, effluent from ICME and CAS processes presented relatively high acute toxicity and genotoxicity, because various heterocyclic and polycyclic aromatic compounds were difficult to be degraded in these processes. Therefore, it was suggested that MEBR was a potential and feasible process for improving CGW treatment and minimizing ecological risk.

Bactericidal activity and mechanisms of BiOBr-AgBr under both dark and visible light irradiation conditions.

BiOBr-AgBr hybrid photocatalysts were synthesized via a facile precipitation and in-situ ion exchange method at room temperature. The as-synthesized photocatalysts were well characterized with different techniques. The disinfection activities of BiOBr-AgBr towards model bacterial strain Gram-negative Escherichia coli (E. coli) were tested under both dark and visible light irradiation conditions. 1 × 107 CFU/mL of E. coli cells could be completely inactivated by BiOBr-AgBr with the optimal silver amount (BiOBr-0.5AgBr) in 24 min under visible light irradiation, while 1.5 log CFU/mL decrease of viable cell density was achieved at the same experiment duration under dark condition. Obviously, with the visible light irradiation, the bactericidal efficiency BiOBr-0.5AgBr was significantly enhanced. The subsequent disinfection mechanism analysis showed that Ag+ released from BiOBr-0.5AgBr did not contribute to E. coli inactivation, while reactive oxygen species including h+, surfaced bounded OH, O2-, and H2O2 were found to play important roles in the disinfection process. The presence of dissolved O2 and the direct contact of cells with photocatalysts was found to be essential for the disinfection process. The reactive species induced the destruction of cell membrane, thus led to the death of bacteria. In addition, BiOBr-0.5AgBr exhibited good bactericidal activity within a wide pH range (5-9) and contained effective antibacterial activity even in fifth consecutive reuse cycles.