Bacterial Metabarcoding of Raw Palm Sap Samples from Bangladesh with Nanopore Sequencing.

The traditional practice of harvesting and processing raw date palm sap is not only culturally significant but also provides an essential nutritional source in South Asia. However, the potential for bacterial or viral contamination from animals and environmental sources during its collection remains a serious and insufficiently studied risk. Implementing improved food safety measures and collection techniques could mitigate the risk of these infections. Additionally, the adoption of advanced food analytical methods offers the potential to identify pathogens and uncover the natural bacterial diversity of these products. The advancement of next-generation sequencing (NGS) technologies, particularly nanopore sequencing, offers a rapid and highly mobile solution. In this study, we employed nanopore sequencing for the bacterial metabarcoding of a set of raw date palm sap samples collected without protective coverage against animals in Bangladesh in 2021. We identified several bacterial species with importance in the natural fermentation of the product and demonstrated the feasibility of this NGS method in the surveillance of raw palm sap products. We revealed two fermentation directions dominated by either Leuconostoc species or Lactococcus species in these products at the first 6 h from harvest, along with opportunistic human pathogens in the background, represented with lower abundance. Plant pathogens, bacteria with the potential for opportunistic human infection and the sequences of the Exiguobacterium genus are also described, and their potential role is discussed. In this study, we demonstrate the potential of mobile laboratory solutions for food safety purposes in low-resource areas.

Plasmid sequence dataset of multidrug-resistant Enterobacterales isolated from hospital effluents and wastewater treatment plant.

We present plasmid sequences of 21 multidrug resistant isolates of Enterobacterales belonging to Escherichia coli (n=10), Klebsiella pneumoniae (n=9), Klebsiella oxytoca (n=1), and Citrobacter freundii (n=1). The isolates originated from effluent collected from hospital sewer pipes and from a wastewater treatment plant (WWTP) in a southwestern Hungarian city. Isolation was carried out using eosin methylene blue agar supplemented with ceftriaxone and the isolates were identified with MALDI-TOF MS. Screening for multidrug resistance was conducted by determining susceptibility to four chemical classes namely, beta-lactams, aminoglycoside, fluoroquinolone, and sulfonamide. Plasmid DNA was isolated by alkaline lysis method using the Monarch plasmid DNA miniprep kit from freshly grown pure colonies. Molecular typing and Illumina sequencing of plasmid DNA of multiresistant strains were performed. After the assembly of contigs, genes localized on plasmid sequences were determined and functionally annotated. These reconstructed plasmid sequences supplemented with gene functional annotations were deposited in the Mendeley data. Using these datasets different plasmid incompatibility groups were identified. These conjugative plasmids appear to play a key role in the transmission of multiple resistance genes in enteric bacteria via wastewater. The presented data may provide useful insight on the correlations between environmental antibiotic contamination and the development of bacterial resistance, which poses a serious public health threat.

Well-Trained Elders Have Antioxidant Responses and an Equal Magnitude of EIMD as Young Adults.

Aim The aim of the study was to investigate acute and chronic effects of a two-week eccentric concentric, dynamometric training concerning the time-course changes of blood antioxidant parameters (total antioxidant capacity, catalase enzyme activity, thiol concentration), and to compare the adaptability of young and older muscle to this type of training. Methods Seventeen moderately trained young and older men participated in this research. Subjects performed six eccentric concentric exercise bouts during the training period and maximal voluntary isometric contraction torque, plasma CK and intensity of muscle soreness were determined before and 24 h after the first exercise. During five testing sessions (baseline, 24 h, 48 h, week 1, week 2) the level of blood antioxidants were measured. Results No significant changes were registered in total antioxidant capacity and catalase enzyme activity for any time points; furthermore, no difference was found between groups during the training period. However, total thiol concentrations measured two weeks after the first exercise bout significantly differed between the young and elderly groups. Plasma CK and the subjective intensity of soreness elevated significantly 24 h following the first training, while maximal voluntary isometric contraction torque decreased at the same time. Conclusions Our results do not support previous findings that chronic, short-term eccentric concentric training programs enhance the antioxidant defense of well-trained older and young men. This type and setting of exercise did not cause a different time course of changes in the markers of exercise-induced muscle damage (EIMD) in the studied population. Subjects may already have adapted to maintain constant levels of antioxidants and isometric torque due to their active lifestyle.

Occurrence of antibiotics and bacterial resistance genes in wastewater: resistance mechanisms and antimicrobial resistance control approaches.

Antimicrobial pharmaceuticals are classified as emergent micropollutants of concern, implying that even at low concentrations, long-term exposure to the environment can have significant eco-toxicological effects. There is a lack of a standardized regulatory framework governing the permissible antibiotic content for monitoring environmental water quality standards. Therefore, indiscriminate discharge of antimicrobials at potentially active concentrations into urban wastewater treatment facilities is rampant. Antimicrobials may exert selective pressure on bacteria, leading to resistance development and eventual health consequences. The emergence of clinically important multiple antibiotic-resistant bacteria in untreated hospital effluents and wastewater treatment plants (WWTPs) has been linked to the continuous exposure of bacteria to antimicrobials. The levels of environmental exposure to antibiotics and their correlation to the evolution and spread of resistant bacteria need to be elucidated to help in the formulation of mitigation measures. This review explores frequently detected antimicrobials in wastewater and gives a comprehensive coverage of bacterial resistance mechanisms to different antibiotic classes through the expression of a wide variety of antibiotic resistance genes either inherent and/or exchanged among bacteria or acquired from the reservoir of antibiotic resistance genes (ARGs) in wastewater systems. To complement the removal of antibiotics and ARGs from WWTPs, upscaling the implementation of prospective interventions such as vaccines, phage therapy, and natural compounds as alternatives to widespread antibiotic use provides a multifaceted approach to minimize the spread of antimicrobial resistance.

Characterization of ß-Lactamases and Multidrug Resistance Mechanisms in Enterobacterales from Hospital Effluents and Wastewater Treatment Plant.

Antimicrobials in wastewater promote the emergence of antibiotic resistance, facilitated by selective pressure and transfer of resistant genes. Enteric bacteria belonging to Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter cloacae, and Citrobacter species (n = 126) from hospital effluents and proximate wastewater treatment plant were assayed for susceptibility to four antimicrobial classes. The ß-lactamase encoding genes harbored in plasmids were genotyped and the plasmids were sequenced. A multidrug resistance phenotype was found in 72% (n = 58) of E. coli isolates, 70% (n = 43) of Klebsiella species isolates, and 40% (n = 25) of Enterobacter and Citrobacter species. Moreover, 86% (n = 50) of E. coli, 77% (n = 33) of Klebsiella species, and 25% (n = 4) of Citrobacter species isolates phenotypically expressed extended spectrum ß-lactamase. Regarding ESBL genes, blaCTX-M-27 and blaTEM-1 were found in E. coli, while Klebsiella species harbored blaCTX-M-15, blaCTX-M-30, or blaSHV-12. Genes coding for aminoglycoside modifying enzymes, adenylyltransferases (aadA1, aadA5), phosphotransferases (aph(6)-1d, aph(3″)-Ib), acetyltransferases (aac(3)-IIa), (aac(6)-Ib), sulfonamide/trimethoprim resistant dihydropteroate synthase (sul), dihydrofolate reductase (dfrA), and quinolone resistance protein (qnrB1) were also identified. Monitoring wastewater from human sources for acquired resistance in clinically important bacteria may provide a cheaper alternative in regions facing challenges that limit clinical surveillance.

Propolis ethanolic extract has double-face in vitro effect on the planktonic growth and biofilm formation of some commercial probiotics.

This study investigated the in vitro effect of propolis ethanolic extract (PEE) on planktonic growth and biofilm forming abilities of five commercial probiotics (Enterol, Protexin, Normaflore, BioGaia and Linex). Broth microdilution method was used to investigate the susceptibility of the microbes of five commercial probiotics to PEE. Crystal violet assay was used for the quantitative assessment of biofilm formation and mature biofilm eradication tests. Effect of PEE on autoaggregation ability and swarming motility of Normaflore microbes was determined. Planktonic forms of probiotics showed varied susceptibilities with minimal inhibitory concentration values in the range of 100-800 µg/mL of PEE. However, low PEE concentrations significantly enhanced the planktonic growth of Linex and BioGaia microbes. Biofilm studies revealed that Enterol and Protexin were non-biofilm formers, while BioGaia, Linex and Normaflore showed weak biofilms, which were inhibited by 12.5, 25, and 800 µg/mL of PEE, respectively. PEE revealed double-face effect on the biofilms of Normaflore and Linex, which were enhanced at low concentrations of PEE and inhibited at higher concentrations. Interestingly, Normaflore biofilms were shifted from weak to strong biofilms at low PEE concentrations (12.5, 25, and 50 µg/mL). In conclusion, PEE has strain dependent controversial effects on the planktonic growth and biofilm forming ability of the tested probiotics, although high concentrations have inhibitory effect on all of them, low concentrations may have strain dependent prebiotic effect.

Cytotoxic Action of Artemisinin and Scopoletin on Planktonic Forms and on Biofilms of Candida Species.

We investigated the antifungal activities of purified plant metabolites artemisinin (Ar) and scopoletin (Sc) including inhibition, effects on metabolic activities, viability, and oxidative stress on planktonic forms and on preformed biofilms of seven Candida species. The characteristic minimum inhibitory concentration (MIC90) of Ar and Sc against Candida species ranged from 21.83-142.1 µg/mL and 67.22-119.4 µg/mL, respectively. Drug concentrations causing ≈10% CFU decrease within 60 minutes of treatments were also determined (minimum effective concentration, MEC10) using 100-fold higher CFUs than in the case of MIC90 studies. Cytotoxic effects on planktonic and on mature biofilms of Candida species at MEC10 concentrations were further evaluated with fluorescent live/dead discrimination techniques. Candida glabrata, Candida guilliermondii, and Candida parapsilosis were the species most sensitive to Ar and Sc. Ar and Sc were also found to promote the accumulation of intracellular reactive oxygen species (ROS) by increasing oxidative stress at their respective MEC10 concentrations against the tested planktonic Candida species. Ar and Sc possess dose-dependent antifungal action but the underlying mechanism type (fungistatic and fungicidal) is not clear yet. Our data suggest that Ar and Sc found in herbal plants might have potential usage in the fight against Candida biofilms.

Antioxidant and antimicrobial properties of randomly methylated ß cyclodextrin - captured essential oils.

Free essential oils and their active components have a low physiochemical stability and low aqueous solubility which limit their applications as food preservatives and in packaging industry. The aim of this study was to characterize the physicochemical properties, antioxidant activities and antimicrobial activity of randomly methylated ß cyclodextrin (RAMEB) encapsulated thyme oil, lemon balm oil, lavender oil, peppermint oil and their active components that include thymol, citral, linalool, menthol and borneol. Inclusion complex formation of essential oils (EOs) and RAMEB were evaluated by several methods. Antioxidant capacities of RAMEB-EOs/components were reported to be more stable than free EOs/components (P < 0.05). Rapid SYBR green I/propidium iodide live/dead microbial cellular discrimination assay for Schizosaccharomyces pombe, Escherichia coli and Staphylococcus aureus showed similar results when compared with flow cytometry analysis (P < 0.01) suggesting that our novel microplate fluorescence method could be applied for the fast live/dead microbial discrimination in antimicrobial assays.

Transcriptome-Based Modeling Reveals that Oxidative Stress Induces Modulation of the AtfA-Dependent Signaling Networks in Aspergillus nidulans.

To better understand the molecular functions of the master stress-response regulator AtfA in Aspergillus nidulans, transcriptomic analyses of the atfA null mutant and the appropriate control strains exposed to menadione sodium bisulfite- (MSB-), t-butylhydroperoxide- and diamide-induced oxidative stresses were performed. Several elements of oxidative stress response were differentially expressed. Many of them, including the downregulation of the mitotic cell cycle, as the MSB stress-specific upregulation of FeS cluster assembly and the MSB stress-specific downregulation of nitrate reduction, tricarboxylic acid cycle, and ER to Golgi vesicle-mediated transport, showed AtfA dependence. To elucidate the potential global regulatory role of AtfA governing expression of a high number of genes with very versatile biological functions, we devised a model based on the comprehensive transcriptomic data. Our model suggests that an important function of AtfA is to modulate the transduction of stress signals. Although it may regulate directly only a limited number of genes, these include elements of the signaling network, for example, members of the two-component signal transduction systems. AtfA acts in a stress-specific manner, which may increase further the number and diversity of AtfA-dependent genes. Our model sheds light on the versatility of the physiological functions of AtfA and its orthologs in fungi.

Linalool-induced oxidative stress processes in the human pathogen Candida albicans.

The present study investigated the linalool (Lol)-induced effects in acute toxicity tests in the human pathogen Candida albicans (C. albicans). Lol treatments induced reduced germ tube formation of the pathogen, which plays a crucial role in the virulence. In comparison with the untreated control, the exposure of 107 cells ml-1 to 0.7 mM or 1.4 mM Lol for one hour induced 20% and 30% decrements, respectively, in the colony-forming ability. At the same time, these treatments caused dose-dependent decrease in the levels of superoxide anion radical and total reactive oxygen species, while there was 1.5 and 1.8-fold increases in the concentrations of peroxides and lipid peroxides, respectively, indicating oxidative stress induction in the presence of Lol. Lol treatments resulted in different adaptive modifications of the antioxidant system. In 0.7 mM-treated cells, decreased specific activities of superoxide dismutase and catalase were detected, while exposure to 1.4 mM Lol resulted in the up-regulation of catalase, glutathione reductase and glutathione peroxidases.

Effects of clary sage oil and its main components, linalool and linalyl acetate, on the plasma membrane of Candida albicans: an in vivo EPR study.

The effects of clary sage (Salvia sclarea L.) oil (CS-oil), and its two main components, linalool (Lol) and linalyl acetate (LA), on cells of the eukaryotic human pathogen yeast Candida albicans were studied. Dynamic and thermodynamic properties of the plasma membrane were investigated by electron paramagnetic resonance (EPR) spectroscopy, with 5-doxylstearic acid (5-SASL) and 16-SASL as spin labels. The monitoring of the head group regions with 5-SASL revealed break-point frequency decrease in a temperature dependent manner of the plasma membrane between 9.55 and 13.15 °C in untreated, in CS-oil-, Lol- and LA-treated membranes. The results suggest a significant increase in fluidity of the treated plasma membranes close to the head groups. Comparison of the results observed with the two spin labels demonstrated that CS-oil and LA induced an increased level of fluidization at both depths of the plasma membrane. Whereas Lol treatment induced a less (1 %) ordered bilayer organization in the superficial regions and an increased (10 %) order of the membrane leaflet in deeper layers. Acute toxicity tests and EPR results indicated that both the apoptotic and the effects exerted on the plasma membrane fluidity depended on the composition and chemical structure of the examined materials. In comparison with the control, treatment with CS-oil, Lol or LA induced 13.0, 12.3 and 26.4 % loss respectively, of the metabolites absorbing at 260 nm, as a biological consequence of the plasma membrane fluidizing effects. Our results confirmed that clary sage oil causes plasma membrane perturbations which leads to cell apoptosis process.

Regulation of the antioxidant system in cells of the fission yeast Schizosaccharomyces pombe after combined treatment with patulin and citrinin.

The effects of combined treatment with patulin (PAT) and citrinin (CTN) on Schizosaccharomyces pombe cells were investigated in acute toxicity tests. In comparison with the controls the exposure of fission yeast cells (10(7) cells ml(-1)) to PAT + CTN (250 µM each) for 1 h at a survival rate of 66.6% significantly elevated the concentration of total reactive oxygen species (ROS) via increased levels of peroxides without affecting the concentrations of superoxides or the hydroxyl radical. This treatment induced a 3.08-fold increase in the specific concentration of glutathione and elevated specific activities of catalase and glutathione S-transferase, while at the same time the activity of glutathione reductase decreased. The pattern of the ROS was the same as that induced by CTN (Máté et al., 2014), while the presence of PAT in the PAT + CTN combination treatment modified the activities of the antioxidant system (Papp et al., 2012) in comparison with the individual PAT or CTN treatment, suggesting toxin-specific regulation of glutathione and the enzymes of the antioxidant system and the possibility that the transcription factor (pap1 and atf1) -regulated processes might be influenced directly by ROS.

Regulation of unbalanced redox homeostasis induced by the expression of wild-type HIV-1 viral protein R (NL4-3Vpr) in fission yeast.

The wild-type viral protein R (Vpr) of human immunodeficiency virus type 1 exerts multiple effects on cellular activities during infection, including the induction of cell cycle G2 arrest and the death of human cells and cells of the fission yeast Schizosaccharomyces pombe. In this study, wild-type Vpr (NL4-3Vpr) integrated as a single copy gene in S. pombe chromosome was used to investigate the molecular impact of Vpr on cellular oxidative stress. NL4-3Vpr triggered an atypical response in early (14-h), and a wellregulated oxidative stress response in late (35-h) log-phase cultures. Specifically, NL4-3Vpr expression induced oxidative stress in the 14-h cultures leading, to decreased levels of superoxide anion (O(2)(·-)), hydroxyl radical (·OH) and glutathione (GSH), and significantly decreased activities of catalase, glutathione peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase and glutathione S-transferase. In the 35-h cultures, elevated levels of O(2)(·-) and peroxides were accompanied by increased activities of most antioxidant enzymes, suggesting that the Vpr-induced unbalanced redox state of the cells might contribute to the adverse effects in HIV-infected patients.

Regulation of oxidative stress-induced cytotoxic processes of citrinin in the fission yeast Schizosaccharomyces pombe.

In this study, the citrinin (CTN)-induced accumulation of reactive oxygen species (ROS) and the regulation of the activities of antioxidant enzymes were investigated in acute toxicity tests in Schizosaccharomyces pombe. 30% of the CTN was accumulated by the cells in 1000 µM CTN solution. In comparison with the control, exposure of 10(7) cells ml(-1) to 1000 µM CTN for 60 min at pH = 4.5 induced significantly (p < 1%) elevated levels of peroxides and total ROS, but not of superoxide or hydroxyl radicals, while there was a 3-fold increase in the concentration of glutathione. ROS-induced adaptation processes at cell and molecular levels via activation of the redox-sensitive transcription factors Pap1 and (in part) Atf1 resulted in significantly increased specific activities of glutathione peroxidases, glucose-6-phosphate dehydrogenase and glutathione S-transferase and in decreased levels of catalase and glutathione reductase, but no changes were detected in the activities of superoxide dismutases. This treatment caused a G2/M cell cycle arrest and elevated the number of fragmented nuclei, which is one of the markers of apoptosis. Comparison of these results with those for the positive control, 200 µM H2O2, suggested that CTN induced a medium level of oxidative stress.

tert-Butyl hydroperoxide-induced differing plasma membrane and oxidative stress processes in yeast strains BY4741 and erg5Δ.

The molecular mechanism of tert-butyl hydroperoxide (t-BuOOH) elicited cytotoxicity and the background of t-BuOOH sensitivity were studied in the Saccharomyces cerevisiae ergosterol-less gene deletion mutant erg5Δ and its parental strain BY4741. In comparison to BY4741, untreated erg5Δ cells exhibited alterations in sterol and fatty acid compositions of the plasma membrane, as reflected by the inherent amphotericin B resistance, an elevated level (31%) of plasma membrane rigidity and a decreased uptake of glycerol. Surprisingly, the untreated erg5Δ cells exhibited an unbalanced intracellular redox state, accompanied by the continuous upregulation of the antioxidant enzymes Mn superoxide dismutase, catalase, and glutathione S-transferase, which resulted in decreased specific concentrations of superoxide and peroxides and elevated levels of the hydroxyl radical and thiols. The 2.5-fold sensitivity of erg5Δ to t-BuOOH suggested that the oxidative stress adaptation processes of the mutant could not restore the redox homeostasis of the cells and there is an overlap between sterol and redox homeostases. t-BuOOH treatment of both strains induced adaptive modification of the sterol and fatty acid compositions, increased the plasma membrane fluidity and elevated the specific activities of most antioxidant enzymes through specific regulation processes in a strain-dependent manner.

Adaptation to tert-butyl hydroperoxide at a plasma membrane level in the fission yeast Schizosaccharomyces pombe parental strain and its t-BuOOH-resistant mutant.

The one-gene mutant hyd1-190 of the fission yeast Schizosaccharomyces pombe displayed four-fold resistance to tert-butyl hydroperoxide (t-BuOOH) in comparison with its parental strain hyd(+). The cells of hyd1-190 exhibited a quantitative alteration in the sterol content and hence in the fatty acid composition of the plasma membrane, reflected in a two-fold amphotericin B sensitivity, increased rigidity of the plasma membrane, revealed by an elevated (Δ7.9 °C) phase-transition temperature, measured by means of electron paramagnetic resonance spectroscopy, and a significantly decreased uptake of glycerol. Treatment of the strains with a subinhibitory concentration (0.2 mM) of t-BuOOH induced adaptation via modification of the sterol and fatty acid compositions, resulting in increased (Δ3.95 °C) and decreased (Δ6.83 °C) phase-transition temperatures of the hyd(+) and hyd1-190 strains, respectively, in order to defend the cells against the consequences of t-BuOOH-induced external oxidative stress. However, in contrast with hyd(+), hyd1-190 lacks the ability to adapt to t-BuOOH at a cell level.

Citrinin-induced fluidization of the plasma membrane of the fission yeast Schizosaccharomyces pombe.

Citrinin (CTN) is a toxic fungal metabolite that is a hazardous contaminant of foods and feeds. In the present study, its acute toxicity and effects on the plasma membrane of Schizosaccharomyces pombe were investigated. The minimum inhibitory concentration of CTN against the yeast cells proved to be 500 µM. Treatment with 0, 250, 500 or 1000 µM CTN for 60 min resulted in a 0%, 2%, 21% or 100% decrease, respectively, in the survival rate of the cell population. Treatment of cells with 0, 100, 500 or 1000 µM CTN for 20 min induced decrease in the phase-transition temperature of the 5-doxylstearic acid-labeled plasma membrane to 16.51, 16.04, 14.18 or 13.98°C, respectively as measured by electron paramagnetic resonance spectroscopy. This perturbation was accompanied by the efflux of essential K⁺ from the cells. The existence of an interaction between CTN and glutathione was detected for the first time by spectrofluorometry. Our observations may suggest a direct interaction of CTN with the free sulfhydryl groups of the integral proteins of the plasma membrane, leading to dose-dependent membrane fluidization. The change in fluidity disturbed the ionic homeostasis, contributing to the death of the cells, which is a novel aspect of CTN cytotoxicity.

Regulation of cytotoxic, non-estrogenic, oxidative stress-induced processes of zearalenone in the fission yeast Schizosaccharomyces pombe.

This study investigates the non-estrogenic mode of zearalenone (ZEA) toxicity in a novel aspect via accumulation of reactive oxygen species (ROS) and the regulation of the activities of antioxidant enzymes in the Schizosaccharomyces pombe in acute toxicity tests. In comparison with the control, 500 µM ZEA treatment caused 66% decrease in the concentration of glutathione (GSH), which was a consequence, in the absence of ZEA-GSH interaction, of the GSH-consuming processes of the antioxidant system; this depletion of GSH initiated a 1.8- and 2.0-fold accumulation of the superoxide anion and hydrogen peroxide, but did not increase the concentration of the hydroxyl radical; ROS-induced adaptation processes via activation of the Pap1 transcription factor resulted in significantly increased activities of superoxide dismutases, catalase, glutathione reductase and glutathione S-transferase, and decreased activities of glutathione peroxidase and glucose-6-phosphate dehydrogenase. This treatment altered the sterol composition of the cells by inducing decreased concentrations of ergosterol, squalene and 24-methylene-24,25-hydrolanosterol, and also elevated the number of fragmented nuclei. Cells strived to correct the unbalanced redox state by regulation of the antioxidant system, but this was not enough to defend the cells from the disturbed sterol composition, the cell cycle arrest, and the fragmentation of nuclei.

Overexpression of the YAP1, PDE2, and STB3 genes enhances the tolerance of yeast to oxidative stress induced by 7-chlorotetrazolo[5,1-c]benzo[1,2,4]triazine.

7-chlorotetrazolo[5,1-c]benzo[1,2,4]triazine (CTBT) is an antifungal agent that induces oxidative stress and enhances the activity of other antifungals with different modes of action. A genome-wide screening of Saccharomyces cerevisiae genomic library in the high-copy-number plasmid revealed three genes, YAP1, PDE2, and STB3, which increased the CTBT tolerance of the parental strain. The YAP1 gene is known to activate many genes in response to oxidants. The PDE2 and STB3 genes encode the high-affinity cAMP phosphodiesterase and the transcription factor recognizing the ribosomal RNA processing element in promoter sequences, respectively. The protective effects of their overexpression against CTBT toxicity was observed in the absence of certain proteins involved in stress responses, cell wall integrity signaling, and chromatin remodeling. The enhanced CTBT tolerance of the YAP1, PDE2, and STB3 transformants was a consequence of their high antioxidant enzyme activities at the beginning of CTBT treatment in comparison with that of the parental strain, for that they inactivated the CTBT-induced reactive oxygen species. These results point to the complex interplay among the oxidant sensing, cAMP-protein kinase A signaling, and transcription reprogramming of yeast cells, leading to their better adaptation to the stress imposed by CTBT.

Regulation of patulin-induced oxidative stress processes in the fission yeast Schizosaccharomyces pombe.

Patulin (PAT), is one of the most widely disseminated mycotoxins found in agricultural products. In this study the PAT-induced accumulation of reactive oxygen species (ROS) and the regulation of the specific activities of antioxidant enzymes were investigated in the single cell eukaryotic organism Schizosaccharomyces pombe. In comparison with the untreated cells, 500 µM PAT treatment caused a 43% decrease in the concentration of the main intracellular antioxidant, glutathione (GSH); this depletion of GSH initiated a 2.44- and a 2.6-fold accumulation of superoxide anion and hydrogen peroxide, respectively, but did not increase the concentration of hydroxyl radicals; the reduction of ROS-induced adaptation processes via the activation of Pap1 transcription factor resulted in significantly increased specific activities of Cu/Zn superoxide dismutase, catalase and glutathione S-transferase to protect the cells against the ROS-induced unbalanced redox state. However, no change was measured in the activities of glutathione reductase, glutathione peroxidase and glucose-6-phosphate dehydrogenase. It seems reasonable to assume that the temporary PAT-induced ROS accumulation plays a crucial role in adaptation processes. The adverse effects of PAT may be exerted mainly through the destruction of cellular membranes and protein/enzyme functions.