Peroxide Resistance Research Articles

The Physiological Status of Acclimatized Simmental Cattle of the Austrian Selection in the Biogeochemical Conditions of the Lower Volga Region

The Lower Volga region, including Astrakhan, Volgograd and Saratov regions of the Russian Federation, is characterized by a deficit of iodine, selenium and cobalt in the main components of biogeocenoses. In 2000-2016 in soil, plants, water, organs and tissues of ruminants (total 2911 samples), selected in the Astrakhan region, the atomic adsorption spectrophotometry (Hitachi 180-50, Japan) was used to determine the content of manganese, cobalt, zinc, copper, selenium, iodine, calcium, phosphorus. In addition to iodine, selenium and cobalt deficiency, low copper (from 1.1 to 19.0 mg/kg of dry matter) and molybdenum (within 0.2±12.8 mg/kg of dry matter) were found in the plants of the region. In the hay of natural lands an increased content of calcium and phosphorus was found – 2.6 and 1.2 times higher compared to the recommended norms. In the studied water samples the excess of hydrochemical parameters on hardness – in 4.4 times, magnesium content – 2.4 times, chlorides – 1.4 times, and the presence of ammonia salt was established. The current biogeochemical situation in Astrakhan region is stressful for Simmental cattle imported from Austria, where the climate and composition of plant feed is different. To assess the physiological status of imported animals 5 different age groups of Simmentals were selected 10 heads in each: 1-4 months old calves, bulls on fattening, heifers and cows. The hematological parameters, alkaline reserve, total calcium content in the blood plasma (serum), inorganic phosphorus, vitamins A, E, ascorbic acid, total protein, total lipids, cholesterol, glucose, adrenocorticosterone, cortisol, thyroxine, diene conjugates, malonic dialdehyde, Schiff bases, catalase activity, superoxide dismutase and glutathione peroxidase in blood, peroxide resistance of erythrocytes were determined in the animals. The number of erythrocytes in the blood of cows exceeded the upper limit of the physiological norm by 17.2%, the concentration of hemoglobin – by 42.1, in all observed animals there was a shift of leukoformula to the right. Biochemical parameters of blood in all age groups of cattle were on the lower limit of norm (vitamin A, total protein, alkaline reserve, and the antioxidant enzymes activity) or below norm (glucose, thyroxine, total calcium, inorganic phosphorus), that along with an imbalance in the system “lipid peroxidation-antioxidant protection” was the evidence of incomplete adaptation to new climatic and geochemical conditions of the environment. Changes in the endocrine and metabolic profile of animals are considered as the main reasons for reducing their milk production and incomplete use of genetic potential.

Fruits of plants of Amelanchier genus (Amelanchier Medic) as source of biologically active substances and minerals

An interest in plants of Amelanchier genus is stimulated by the necessity of search for plant sources rich in biologically active substances and possessing the ability to influence different physiological processes in a human organism. The article gives information about places of growth of different species of Amelanchier (Amelanchier Medic) and about the fact that its fruits contain high concentration of free sugars, relatively low level of organic acids, sufficient amounts of various vitamins and provitamins and a complex of mineral substances. Nutritive and biological value of Amelanchier fruits in complex may produce a beneficial effect on different biochemical and physiological processes of normal vital activity of a human organism. The data are given about a positive influence of enteral introduction of polysaccharides isolated from Amelanchier fruits, on different physiological processes that enhance adaptational reserves of an organism of experimental animals. In particular, it was shown that watersoluble polysaccharide complex (WSPC) of Amelanchier fruits activates erythropoiesis increasing the amount of erythrocytes and hemoglobin in blood of experimental animals and raises concentration of iron. WSPC improves physical working capacity and increases the body mass of experimental animals. Addition of watersoluble polysaccharide complex of Amelanchier fruits to blood of a healthy donor increases thermal, osmotic and peroxide resistance of erythrocyte membranes thus protecting cells against damage under action of adverse factors in the experiment. Fruits of plants of Amelanchier genus may be recommended to be used as a food additive or a product in dietary and prophylactic therapy.

Fruits of plants of Amelanchier genus (Amelanchier Medic) as source of biologically active substances and minerals

An interest in plants of Amelanchier genus is stimulated by the necessity of search for plant sources rich in biologically active substances and possessing the ability to influence different physiological processes in a human organism. The article gives information about places of growth of different species of Amelanchier (Amelanchier Medic) and about the fact that its fruits contain high concentration of free sugars, relatively low level of organic acids, sufficient amounts of various vitamins and provitamins and a complex of mineral substances. Nutritive and biological value of Amelanchier fruits in complex may produce a beneficial effect on different biochemical and physiological processes of normal vital activity of a human organism. The data are given about a positive influence of enteral introduction of polysaccharides isolated from Amelanchier fruits, on different physiological processes that enhance adaptational reserves of an organism of experimental animals. In particular, it was shown that watersoluble polysaccharide complex (WSPC) of Amelanchier fruits activates erythropoiesis increasing the amount of erythrocytes and hemoglobin in blood of experimental animals and raises concentration of iron. WSPC improves physical working capacity and increases the body mass of experimental animals. Addition of watersoluble polysaccharide complex of Amelanchier fruits to blood of a healthy donor increases thermal, osmotic and peroxide resistance of erythrocyte membranes thus protecting cells against damage under action of adverse factors in the experiment. Fruits of plants of Amelanchier genus may be recommended to be used as a food additive or a product in dietary and prophylactic therapy.

GlnR Activation Induces Peroxide Resistance in Mycobacterial Biofilms.

Mycobacteria spontaneously form surface-associated multicellular communities, called biofilms, which display resistance to a wide range of exogenous stresses. A causal relationship between biofilm formation and emergence of stress resistance is not known. Here, we report that activation of a nitrogen starvation response regulator, GlnR, during the development of Mycobacterium smegmatis biofilms leads to peroxide resistance. The resistance arises from induction of a GlnR-dependent peroxide resistance (gpr) gene cluster comprising of 8 ORFs (MSMEG_0565-0572). Expression of gpr increases the NADPH to NADP ratio, suggesting that a reduced cytosolic environment of nitrogen-starved cells in biofilms contributes to peroxide resistance. Increased NADPH levels from gpr activity likely support the activity of enzymes involved in nitrogen assimilation, as suggested by a higher threshold of nitrogen supplement required by a gpr mutant to form biofilms. Together, our study uniquely interlinks a nutrient sensing mechanism with emergence of stress resistance during mycobacterial biofilm development. The gpr gene cluster is conserved in several mycobacteria that can cause nosocomial infections, offering a possible explanation for their resistance to peroxide-based sterilization of medical equipment.

Disruption of a Novel Iron Transport System Reverses Oxidative Stress Phenotypes of a dpr Mutant Strain of Streptococcus mutans.

The Dps-like peroxide resistance protein (Dpr) is essential for H2O2 stress tolerance and aerobic growth of the oral pathogen Streptococcus mutans Dpr accumulates during oxidative stress, protecting the cell by sequestering iron ions and thereby preventing the generation of toxic hydroxyl radicals that result from the interaction of iron with H2O2 Previously, we reported that the SpxA1 and SpxA2 regulators positively regulate expression of dpr in S. mutans Using an antibody raised against S. mutans Dpr, we confirmed at the protein level the central and cooperative nature of SpxA1 and SpxA2 regulation in Dpr production. During phenotypic characterization of the S. mutans Δdpr strain, we observed the appearance of distinct colony variants, which sometimes lost the oxidative stress sensitivity typical of Δdpr strains. Whole-genome sequencing of these phenotypically distinct Δdpr isolates revealed that a putative iron transporter operon, smu995-smu998, was a genomic hot spot with multiple single nucleotide polymorphisms identified within the different isolates. Deletion of smu995 or the entire smu995-smu998 operon in the Δdpr background strain completely reversed the oxidative stress-sensitive phenotypes associated with dpr inactivation. Conversely, inactivation of genes encoding the ferrous iron transport system FeoABC did not alleviate phenotypes of the Δdpr strain. Preliminary characterization of strains lacking smu995-smu998, feoABC, and the iron/manganese transporter gene sloABC revealed the interactive nature of these three systems in iron transport but also indicated that there may be additional iron uptake systems in S. mutansIMPORTANCE The dental caries-associated pathogen Streptococcus mutans routinely encounters oxidative stress within the human plaque biofilm. Previous studies revealed that the iron-binding protein Dpr confers protection toward oxidative stress by limiting free iron availability, which is associated with the generation of toxic hydroxyl radicals. Here, we report the identification of spontaneously occurring mutations within Δdpr strains. Several of those mutations were mapped to the operon smu995-smu998, revealing a previously uncharacterized system that appears to be important in iron acquisition. Disruption of the smu995-smu998 operon resulted in reversion of the stress-sensitive phenotype typical of a Δdpr strain. Our data suggest that the Smu995-Smu998 system works along with other known metal transport systems of S. mutans, i.e., FeoABC and SloABC, to coordinate iron uptake.

The roles of two O-donor ligands in the Fe2+-binding and H2O2-sensing by the Fe2+-dependent H2O2 sensor PerR

PerR is a metal-dependent peroxide sensing transcription factor which controls the expression of genes involved in peroxide resistance. The function of Bacillus subtilis PerR is mainly dictated by the regulatory metal ion (Fe2+ or Mn2+) coordinated by three N-donor ligands (His37, His91, and His93) and two O-donor ligands (Asp85 and Asp104). While H2O2 sensing by PerR is mediated by Fe2+-dependent oxidation of N-donor ligand (either His37 or His91), one of the O-donor ligands (Asp104), but not Asp85, has been proposed as the key residue that regulates the sensitivity of PerR to H2O2. Here we systematically investigated the relative roles of two O-donor ligands of PerR in metal-binding affinity and H2O2 sensitivity in vivo and in vitro. Consistent with the previous report, in vitro the D104E-PerR could not sense low levels of H2O2 in the presence of excess Fe2+ sufficient for the formation of the Fe2+-bound D104E-PerR. However, the expression of PerR-regulated reporter fusion was not repressed by D104E-PerR in the presence of Fe2+, suggesting that Fe2+ is not an effective corepressor for this mutant protein in vivo. Furthermore, in vitro metal titration assays indicate that D104E-PerR has a significantly reduced affinity for Fe2+, but not for Mn2+, when compared to wild type PerR. These data indicate that the type of O-donor ligand (Asp vs. Glu) at position 104 is an important determinant in providing high Fe2+-binding affinity required for the sensing of the physiologically relevant Fe2+-levels, in addition to its role in rendering PerR highly sensitive to physiological levels of H2O2. In comparison, the D85E-PerR did not show a perturbed change in Fe2+-binding affinity, however, it displayed a slightly decreased sensitivity to H2O2 both in vivo and in vitro, suggesting that the type of O-donor ligand (Asp vs. Glu) at position 85 may be important for the fine-tuning of H2O2 sensitivity.

Biofilm formation and transcriptome analysis of Streptococcus gallolyticus subsp. gallolyticus in response to lysozyme.

Streptococcus gallolyticus subsp. gallolyticus is a commensal bacterium of the human gastrointestinal tract, and a pathogen causing infective endocarditis and other biofilm-associated infections via exposed collagen. This study focuses on the characterization of the biofilm formation and collagen adhesion of S. gallolyticus subsp. gallolyticus under different conditions. In this study, it has been observed that the isolate UCN 34 is resistant to 20 mg/ml lysozyme in BHI medium, whereas the strain BAA-2069 builds more biofilm in the presence of lysozyme compared to in a control of BHI without lysozyme. A transcriptome analysis with whole genome microarrays of these two isolates in BHI medium with lysozyme compared to control without lysozyme revealed changes in gene expression levels. In the isolate BAA-2069, 67 genes showed increased expression in the presence of lysozyme, while in the isolate UCN 34, 165 genes showed increased expression and 30 genes showed decreased expression through lysozyme treatment. Products of genes which were higher expressed are in involved in transcription and translation, in cell-wall modification, in hydrogen peroxide resistance and in bacterial immunity. Furthermore, the adhesion ability of different strains of S. gallolyticus subsp. gallolyticus to collagen type I and IV was analyzed. Thereby, we compared the adhesion of 46 human isolates with 23 isolates from animals. It was shown that the adhesion ability depends significantly on whether the isolate was isolated from human or animal. For example, high adhesion ability was observed for strain UCN 34 isolated from an infective endocarditis patient, whereas strain DSM 16831 isolated from koala feces adhered only marginally to collagen. Full genome microarray analysis of these two strains revealed strain-dependent gene expression due to adhesion. The expression of 25 genes of a transposon and 15 genes of a phage region in strain DSM 16831 were increased, which corresponds to horizontal gene transfer. Adherence to collagen in strain UCN 34 led to higher expression of 27 genes and lower expression of 31 genes. This was suggestive of a change in nutrient uptake.

The ceramide activated protein phosphatase Sit4 impairs sphingolipid dynamics, mitochondrial function and lifespan in a yeast model of Niemann-Pick type C1

The Niemann-Pick type C is a rare neurodegenerative disease that results from loss-of-function point mutations in NPC1 or NPC2, which affect the homeostasis of sphingolipids and sterols in human cells. We have previously shown that yeast lacking Ncr1, the orthologue of human NPC1 protein, display a premature ageing phenotype and higher sensitivity to oxidative stress associated with mitochondrial dysfunctions and accumulation of long chain bases. In this study, a lipidomic analysis revealed specific changes in the levels of ceramide species in ncr1Δ cells, including decreases in dihydroceramides and increases in phytoceramides. Moreover, the activation of Sit4, a ceramide-activated protein phosphatase, increased in ncr1Δ cells. Deletion of SIT4 or CDC55, its regulatory subunit, increased the chronological lifespan and hydrogen peroxide resistance of ncr1Δ cells and suppressed its mitochondrial defects. Notably, Sch9 and Pkh1-mediated phosphorylation of Sch9 decreased significantly in ncr1Δsit4Δ cells. These results suggest that phytoceramide accumulation and Sit4-dependent signaling mediate the mitochondrial dysfunction and shortened lifespan in the yeast model of Niemann-Pick type C1, in part through modulation of the Pkh1-Sch9 pathway.

Enhancing oxidative stress resistance in Bifidobacterium thermophilum using a novel overexpression vector and transformation protocol

Bifidobacterium thermophilum is encountered in the GI-tract of pigs and infants. Here we provide a transformation protocol for B. thermophilum and a novel expression vector for this species. The protocol resulted in transformation rates of 1×103 transformed cells per μg DNA. Transformation was shown to be dependent on the presence of fructo-oligosaccharides during growth, polyethylene glycol in the electroporation buffer, and on methylation of the vector.The Escherichia coli - B. thermophilum shuttle vector pLFB1012 for heterologous gene expression was constructed harbouring the glyceraldehyde 3-phosphate dehydrogenase promoter from Bifidobacterium longum (Pgap). Activity of the β-glucoronidase gene gusA under control of Pgap could be detected at a 20-fold higher rate compared to the wild type, showing activity of the promoter in B. thermophilum. Thereafter, the B. longum gene bl_1404, previously proposed to be involved in oxidative stress resistance, was cloned under control of the Pgap. The wild type cell numbers of B. thermophilum RBL 67 decreased at least 9 log after a 20-mM H2O2 treatment for 60min whereas the mutant strain expressing bl_1404 showed an increased survival of 2 logs compared to the wild type strain. To our knowledge this is the first report on transformation of B. thermophilum. Further, it is shown that pLFB1002 is suitable for engineering B. thermophilum and that bl_1404 from B. longum is involved in peroxide resistance in bifidobacteria.

STUDY OF COMPOSITION, PHYSICAL AND CHEMICAL PROPERTIES AND BIOLOGICAL ACTIVITY OF POLYSACCHARIDE COMPLEX OF ARCTIUM LAPPA LEAVES

A method of isolation of polysaccharide complex from the leaves of Burdock (Arctium lappa L.) is described in the article. For the first time the qualitative composition of this complex was determined, belonging to the group of heteroglycans. Some of physical and chemical properties of polysaccharide complex were studied. It is shown that polysaccharide complex increases catalase activity and peroxide resistance of the erythrocyte membranes of healthy donors. The study found that polysaccharide complex of Burdock improves physical performance of test animals.

The Staphylococcus aureus SrrAB Regulatory System Modulates Hydrogen Peroxide Resistance Factors, Which Imparts Protection to Aconitase during Aerobic Growth.

The SrrAB two-component regulatory system (TCRS) positively influences the transcription of genes involved in aerobic respiration in response to changes in respiratory flux. Hydrogen peroxide (H2O2) can arise as a byproduct of spontaneous interactions between dioxygen and components of respiratory pathways. H2O2 damages cellular factors including protein associated iron-sulfur cluster prosthetic groups. We found that a Staphylococcus aureus strain lacking the SrrAB two-component regulatory system (TCRS) is sensitive to H2O2 intoxication. We tested the hypothesis that SrrAB manages the mutually inclusive expression of genes required for aerobic respiration and H2O2 resistance. Consistent with our hypothesis, a ΔsrrAB strain had decreased transcription of genes encoding for H2O2 resistance factors (kat, ahpC, dps). SrrAB was not required for the inducing the transcription of these genes in cells challenged with H2O2. Purified SrrA bound to the promoter region for dps suggesting that SrrA directly influences dps transcription. The H2O2 sensitivity of the ΔsrrAB strain was alleviated by iron chelation or deletion of the gene encoding for the peroxide regulon repressor (PerR). The positive influence of SrrAB upon H2O2 metabolism bestowed protection upon the solvent accessible iron-sulfur (FeS) cluster of aconitase from H2O2 poisoning. SrrAB also positively influenced transcription of scdA (ytfE), which encodes for a FeS cluster repair protein. Finally, we found that SrrAB positively influences H2O2 resistance only during periods of high dioxygen-dependent respiratory activity. SrrAB did not influence H2O2 resistance when cellular respiration was diminished as a result of decreased dioxygen availability, and negatively influenced it in the absence of respiration (fermentative growth). We propose a model whereby SrrAB-dependent regulatory patterns facilitate the adaptation of cells to changes in dioxygen concentrations, and thereby aids in the prevention of H2O2 intoxication during respiratory growth upon dixoygen.

The difference in in vivo sensitivity between Bacillus licheniformis PerR and Bacillus subtilis PerR is due to the different cellular environments

PerR, a member of Fur family of metal-dependent regulators, is a major peroxide sensor in many Gram positive bacteria, and controls the expression of genes involved in peroxide resistance. Bacillus licheniformis, a close relative to the well-studied model organism Bacillus subtilis, contains three PerR-like proteins (PerRBL, PerR2 and PerR3) in addition to Fur and Zur. In the present study, we characterized the role of PerRBL in B. licheniformis. In vitro and in vivo studies indicate that PerRBL, like PerRBS, uses either Fe2+ or Mn2+ as a corepressor and only the Fe2+-bound form of PerRBL senses low levels of H2O2 by iron-mediated histidine oxidation. Interestingly, regardless of the difference in H2O2 sensitivity, if any, between PerRBL and PerRBS, B. licheniformis expressing PerRBL or PerRBS could sense lower levels of H2O2 and was more sensitive to H2O2 than B. subtilis expressing PerRBL or PerRBS. This result suggests that the differences in cellular milieu between B. subtilis and B. licheniformis, rather than the intrinsic differences in PerRBS and PerRBLper se, affect the H2O2 sensing ability of PerR inside the cell and the H2O2 resistance of cell. In contrast, B. licheniformis and B. subtilis expressing Staphylococcus aureus PerR (PerRSA), which is more sensitive to H2O2 than PerRBL and PerRBS, were more resistant to H2O2 than those expressing either PerRBL or PerRBS. This result indicates that the sufficient difference in H2O2 susceptibility of PerR proteins can override the difference in cellular environment and affect the resistance of cell to H2O2.

Functional analysis of a novel hydrogen peroxide resistance gene in Lactobacillus casei strain Shirota.

Lactic acid bacteria have a variety of mechanisms for tolerance to oxygen and reactive oxygen species, and these mechanisms differ among species. Lactobacillus casei strain Shirota grows well under aerobic conditions, indicating that the various systems involved in oxidative stress resistance function in this strain. To elucidate the mechanism of oxidative stress resistance in L. casei strain Shirota, we examined the transcriptome response to oxygen or hydrogen peroxide exposure. We then focused on an uncharacterized gene that was found to be up-regulated by both oxygen and hydrogen peroxide stress; we named the gene hprA1 (hydrogen peroxide resistance gene). This gene is widely distributed among lactobacilli. We investigated the involvement of this gene in oxidative stress resistance, as well as the mechanism of tolerance to hydrogen peroxide. Growth of L. casei MS105, an hprA1-disrupted mutant, was not affected by oxygen stress, whereas the survival rate of MS105 after hydrogen peroxide treatment was markedly reduced compared to that of the wild-type. However, the activity of MS105 in eliminating hydrogen peroxide was similar to that of the wild-type. We cloned hprA1 from L. caseiShirota and purified recombinant HprA1 protein from Escherichia coli. We demonstrated that the recombinant HprA1 protein bound to iron and prevented the formation of a hydroxyl radical in vitro. Thus, HprA1 protein probably contributes to hydrogen peroxide tolerance in L. casei strain Shirota by binding to iron in the cells and preventing the formation of a hydroxyl radical.

DNA Phosphorothioate Modification Plays a Role in Peroxides Resistance in Streptomyces lividans.

DNA phosphorothioation, conferred by dnd genes, was originally discovered in the soil-dwelling bacterium Streptomyces lividans, and thereafter found to exist in various bacterial genera. However, the physiological significance of this sulfur modification of the DNA backbone remains unknown in S. lividans. Our studies indicate that DNA phosphorothioation has a major role in resistance to oxidative stress in the strain. Although Streptomyces species express multiple catalase/peroxidase and organic hydroperoxide resistance genes to protect them against peroxide damage, a wild type strain of S. lividans exhibited two-fold to 10-fold higher survival, compared to a dnd− mutant, following treatment with peroxides. RNA-seq experiments revealed that, catalase and organic hydroperoxide resistance gene expression were not up-regulated in the wild type strain, suggesting that the resistance to oxidative stress was not due to the up-regulation of these genes by DNA phosphorothioation. Quantitative RT-PCR analysis was conducted to trace the expression of the catalase and the organic hydroperoxide resistance genes after peroxides treatments. A bunch of these genes were activated in the dnd− mutant rather than the wild type strain in response to peroxides. Moreover, the organic hydroperoxide peracetic acid was scavenged more rapidly in the presence than in the absence of phosphorothioate modification, both in vivo and in vitro. The dnd gene cluster can be up-regulated by the disulfide stressor diamide. Overall, our observations suggest that DNA phosphorothioate modification functions as a peroxide resistance system in S. lividans.

Nucleoid clumping is dispensable for the Dps-dependent hydrogen peroxide resistance in Staphylococcus aureus.

Dps family proteins have the ferroxidase activity that contributes to oxidative stress resistance. In addition, a part of Dps family proteins including Escherichia coli Dps and Staphylococcus aureus MrgA (metallo regulon gene A) bind DNA and induce the structural change of the nucleoid. We previously showed that a mutated MrgA with reduced ferroxidase activity was unable to contribute to the hydrogen peroxide (H2O2) and UV resistance in S. aureus, suggesting that the nucleoid clumping by MrgA is not sufficient for the resistance. However, it remained elusive whether the nucleoid clumping is dispensable for the resistance. Here, we aimed to clarify this question by employing the E. coli Dps lacking DNA-binding activity, DpsΔ18. Staphylococcal nucleoid was clumped by E. coli Dps, but not by DpsΔ18. H2O2 stress assay indicated that Dps and DpsΔ18 restored the reduced susceptibility of S. aureus ΔmrgA. Thus, we concluded that the staphylococcal nucleoid clumping is dispensable for the Dps-mediated H2O2 resistance. In contrast, Dps was unable to complement S. aureus ΔmrgA in the UV resistance, suggesting the MrgA function that cannot be compensated for by E. coli Dps.

Sulfonated poly(ether imide)s with fluorenyl and trifluoromethyl groups: Application in microbial fuel cell (MFC)

A series of fluorenyl and trifluoromethyl groups containing co-poly(ether imide)s (S-co-PIs) have been prepared from a new diamine monomer; 9,9-bis(3-methoxy-4-(4-amino(3-trifluoro-methyl)biphenoxy)phenyl)-9H-fluorene (APHPF). The polymers were prepared by the polycondensation reaction of 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA) with two different diamines; APHPF and 4,4′-diaminostilbene-2,2′-disulfonicacid (DSDSA) as a co-monomer. The monomer and polymers were well characterized by 1H NMR and ATR-FTIR spectroscopies. The co-polymers were soluble in various organic solvents and membranes were prepared from solution cast route. The S-co-PIs showed high thermal and mechanical stability. TEM and AFM results supports the formation of phase separated morphology with well separated ionic-clusters. All these S-co-PIs displayed reasonably high proton conductivity. One of the copolymers (DAN-80; IECw ∼2.27meqg−1) exhibited a proton conductivity as high as 149mScm−1 which was comparable to that of Nafion® 117 (165mScm−1) at 80°C. The co-polymers maintain a good balance between water-uptake and swelling ratios and peroxide resistance. Microbial Fuel Cell (MFC) performance of the co-polymers were evaluated DAN-80 exhibited a similar performance like Nafion® 117 under similar test condition.

Dual promoters of the major catalase (KatA) govern distinct survival strategies of Pseudomonas aeruginosa.

KatA is the major catalase required for hydrogen peroxide (H2O2) resistance and acute virulence in Pseudomonas aeruginosa PA14, whose transcription is driven from the promoter (katAp1) located at 155 nucleotide (nt) upstream of the start codon. Here, we identified another promoter (katAp2), the +1 of which was mapped at the 51 nt upstream of the start codon, which was responsible for the basal transcription during the planktonic culture and down-regulated upon H2O2 treatment under the control by the master regulator of anaerobiosis, Anr. To dissect the roles of the dual promoters in conditions involving KatA, we created the promoter mutants for each -10 box (p1m, p2m, and p1p2m) and found that katAp1 is required for the function of KatA in the logarithmic growth phase during the planktonic culture as well as in acute virulence, whereas katAp2 is required for the function of KatA in the stationary phase as well as in the prolonged biofilm culture. This dismantling of the dual promoters of katA sheds light on the roles of KatA in stress resistance in both proliferative and growth-restrictive conditions and thus provides an insight into the regulatory impacts of the major catalase on the survival strategies of P. aeruginosa.

Involvement of FST1 from Fusarium verticillioides in virulence and transport of inositol.

Fumonisin B1 (FB1), a polyketide mycotoxin produced by Fusarium verticillioides during the colonization of maize kernels, is detrimental to human and animal health. FST1 encodes a putative protein with 12 transmembrane domains; however, its function remains unknown. The FST1 gene is highly expressed by the fungus in the endosperm of maize kernels compared with the levels of expression in germ tissues. Previous research has shown that FST1 affects FB1 production, virulence, hydrogen peroxide resistance, hydrophobicity and macroconidia production. Here, we examine the phylogeny of FST1, its expression in a Saccharomyces cerevisiae strain lacking a functional myo-inositol transporter (ITR1) and the effect of amino acid changes in the central loop and C-terminus regions of FST1 on functionality. The results indicate that expression of FST1 in an ITR1 mutant strain restores growth on myo-inositol medium to wild-type levels and restores the inhibitory effects of FB1, suggesting that FST1 can transport both myo-inositol and FB1 into yeast cells. Our results with engineered FST1 also indicate that amino acids in the central loop and C-terminus regions are important for FST1 functionality in both S. cerevisiae and F. verticillioides. Overall, this research has established the first characterized inositol transporter in filamentous fungi and has advanced our knowledge about the global regulatory functions of FST1.

Hydrogen peroxide, nitric oxide and UV RESISTANCE LOCUS8 interact to mediate UV-B-induced anthocyanin biosynthesis in radish sprouts.

The cross talk among hydrogen peroxide (H2O2), nitric oxide (NO) and UV RESISTANCE LOCUS8 (UVR8) in UV-B-induced anthocyanin accumulation in the hypocotyls of radish sprouts was investigated. The results showed that UV-B irradiation significantly increased the anthocyanin accumulation and the expression of UVR8, and a similar trend appeared in radish sprouts subjected to cadmium, chilling and salt stresses regardless of light source. However, these responses disappeared under dark exposure. These results suggest that abiotic stress-induced anthocyanin accumulation and UVR8 expression were light-dependent. Moreover, abiotic stresses all enhanced the production of H2O2 and exogenous H2O2 addition significantly increased the anthocyanin concentration and UVR8 transcription, while these increases were severely inhibited by addition of dimethylthiourea (DMTU, a chemical trap for H2O2). It seems to suggest that H2O2 played an important role in the anthocyanin biosynthesis. Furthermore, addition of 0.5 mM sodium nitroprusside (SNP, a NO-releasing compound) substantially induced the anthocyanin accumulation, and H2O2-induced anthocyanin accumulation and UVR8 expression were significantly suppressed by co-treatment with 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl (PTIO, a NO scavenger), which was parallel with the expression of anthocyanin biosynthesis-related transcription factors and structural genes. All these results demonstrate that both H2O2 and NO are involved in UV-B-induced anthocyanin accumulation, and there is a crosstalk between them as well as a classical UVR8 pathway.

OXIDATIVE STRESS AND RESISTANCE OF ERYTHROCYTES MEMBRANES IN PATIENTS WITH CHRONIC KIDNEY DISEASE STAGE VD DEPENDING ON MODALITY OF RENAL REPLACEMENT THERAPY

The aim of the research was to study the effect ofoxidative factors impact and modality of renal replacement therapy (BBT) on indices ofoxidative stress (OS) and resistance of erythrocytes membranes in patients with chronic kidney disease stage V(CKD VD) and anemie.
 Material and methods. The study involved 68 patients with CKD VD: 14 patients were treated by hemodiafiltration (HDF), 25 patients by hemodialysis (HD) and 29 patients by peritoneal dialysis (PD). The severity ofanemia was assessed according to the KDIGO (2012) criteria. The control group consisted of 30 healthy people of the same age and sex. Along with the standard diagnostic methods, we defined the content of malonic dialdehyde in serum (MDAs) and in erythrocytes (MDAe), the content of ceruloplasmin (CPs), transferrin (TBs) and SH-groups in the blood serum, the index of the OS (IOS), catalase activity in serum (CATs), glucose-6-phosphate dehydrogenase (G-6-PDHe) and total peroxidase activity (TPA) in erythrocyte, peroxide resistance (PR) of red blood cells and erythrocyte membrane permeability (EMP). Statistical analysis was performed using the programs of Microsoft Excel 7.0.
 Results. It has been stated that in the CKD VD patients in compatison with control group the MDAs content increased by 3.3 times and MDAe - 1.2 times, TBs content reduced by 34%, SH-groups - by 31%, TPAe - by 41% and G- 6-FDGe - by 58%, PB-by 60%; 4.6 times increased CATs activity and OSI; 2 times grew peroxide hemolysis (PH) and 1.3 times - EMP. The analysis (depending on the BBT modality) showed that the patients treated by HDF had typical MDAs increase by 3.9 times on a background of CPs by 24%, TBs - 33%, SH-groups - 25%, TPAe - 51%, G-6-PDHe - 42%; the increase in serum OSI - 5.4 times and 2.6 times in erythrocytes, PB - by 3.6 times and CATs activity by 3.5 times; HD group was characterized by the highest value of MDAe, OSI, PH and CATs, along with more expressed decrease of TBs indices, SH-groups, TPA and G-6-FDHe activity compared with rates in patients with HDF. The patients treated with PD had the lowest content of MDAs and the highest values on the background ofTPAe, the significant increase of CPs by 1.7 times and lowest TBs and G-6-PDHe. The patients with PD showed twice lower OS activity by OSI.
 Conclusion. Thus, in patients with CKD VD, who had HD, HDF or PD an anemie was associated with high OS activity and the increased degree of hemolysis. These changes are stipulated by BBT methods: for patients receiving HDF were typical the lowest rates of hemolysis and the highest degree ofprotection for erythrocytes, and for patients treated with HD - the highest OS.