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1.
Abstract Transport of Mn2+ was repressed in Candida utilis cells grown in continuous culture in high-Mn2+ (100 μM Mn2+) medium as compared to cells grown in basic (0.45 μM Mn2+) and low-Mn2+ (< 0.05 μM Mn2+) media. In contrast, no repression of Cu2+ uptake occurred in high-Cu2+-grown (25 μM Cu2+) cells as compared to cells grown in basic medium (0.54 μM Cu2+). Cu2+-limited cells did not hyperaccumulate Cu2+ and there was not significant difference in initial uptake rates for all 3 Cu2+ conditions. Mn2+ uptake appears to be regulated by a mechanism sensitive to the external Mn2+ concentration, whereas Cu2+ transport is not governed in this way by the external Cu2+.  相似文献   

2.
A phage K3-resistant isolate from Escherichia coli P678-54 was devoid of both the OmpA and OmpC proteins but had high levels of the OmpF protein. Associated with these changes, the strain showed increased sensitivity to inhibition by detergents and greatly increased sensitivity to Cu2+. Introduction of the ColV, I-K94 plasmid into this mutant produced a derivative with markedly increased resistance to Cu2+ ions but unchanged detergent sensitivity. Analysis of membranes showed that the ColV, I-K94+ derivative had essentially no OmpF protein in its outer membrane. A ca 36 K outer membrane protein was present which resembled the OmpC protein in size and failure to dissociate in SDS at low temperature. It was distinct from the OmpC protein, however, in failing to allow either tetracycline uptake or the adsorption of T4-type phages. The possible significance of OmpF porin derepression (and its reversal by ColV, I-K94) for enterobacterial survival in aquatic situations is discussed.  相似文献   

3.
Pyoverdine (PvdI) is the major siderophore secreted by Pseudomonas aeruginosa PAOI in order to get access to iron. After being loaded with iron in the extracellular medium, PvdI is transported across the bacterial outer membrane by the transporter, FpvAI. We used the spectral properties of PvdI to show that in addition to Fe3+, this siderophore also chelates, but with lower efficiencies, all the 16 metals used in our screening. Afterwards, FpvAI at the cell surface binds Ag+, Al3+, Cd2+, Co2+, Cu2+, Fe3+, Ga3+, Hg2+, Mn2+, Ni2+ or Zn2+ in complex with PvdI. We used Inductively Coupled Plasma-Atomic Emission Spectrometry to monitor metal uptake in P. aeruginosa : TonB-dependent uptake, in the presence of PvdI, was only efficient for Fe3+. Cu2+, Ga3+, Mn2+ and Ni2+ were also transported into the cell but with lower uptake rates. The presence of Al3+, Cu2+, Ga3+, Mn2+, Ni2+ and Zn2+ in the extracellular medium induced PvdI production in P. aeruginosa . All these data allow a better understanding of the behaviour of the PvdI uptake pathway in the presence of metals other than iron: FpvAI at the cell surface has broad metal specificity at the binding stage and it is highly selective for Fe3+ only during the uptake process.  相似文献   

4.
Washed Escherichia coli ATCC11775 cells were killed by (–)-epigallocatechin (EGC) in the presence of a non- lethal concentration of Cu2+ (1 μmol l−1) without additional H2O2, but not by (–)-epicatechin (EC). EGC alone (< 0·1 mmol l−1) did not reduce the viability of the cells. The survival curve obtained in the presence of EGC and Cu2+ was similar to that obtained in the presence of (–)-adrenaline (EN) and Cu2+.  相似文献   

5.
Effects of mixtures of chloride salts of cadmium, copper and zinc on survival, whole body residues, and histopathology of mummichog, Fundulus heteroclitus (L.), were investigated in synthetic sea water at 20‰ salinity and 20°C. Mixtures of Cu2+ and Zn2+ as indicated by 96 h bioassay studies produced more deaths than expected on the basis of toxicities of individual components. Concentrations of Cd2+ not ordinarily lethal exerted a negative effect on survival of fish intoxicated by salts of copper, zinc, or both.
Atomic absorption determinations of Cd, Cu, and Zn residues in mummichog which survived 96 h exposures to each of these toxicants provided useful indices of total body burdens for these metals. Residues from survivors held in mixtures, especially Cd2+ and Zn2+ mixtures, did not conform to patterns observed for single elements. Whole body aggregates of Cd, Cu, and Zn from dead mummichogs were of limited worth owing to possible accumulation of these metals from the medium after death.
Renal and lateral line canal lesions were noted in all fish subjected to copper concentrations of 1 mg/1 and higher. Renal lesions observed in fish immersed in mixtures of Cu2+ and Cd2+ assumed a damage pattern characteristic of Cd2+; with mixtures of Cu2+ and Zn2+, lesion were typical of Cu2+-induced damage. Lesions induced in lateral line epithelium by Cu2+ were not affected by either Cd2+ or Zn2+. Epithelia lining the oral cavity were necrotized by the caustic action of high levels of Zn2+ (60 mg/1) and of Cu2+ (8 mg/1).  相似文献   

6.
In Escherichia coli , lacZ operon fusions were isolated that were derepressed under iron repletion and repressed under iron depletion. Two fusions were localized in genes that formed an operon whose gene products had characteristics of a binding protein-dependent transport system. The growth defect of these mutants on TY medium containing 5 mM EGTA was compensated for by the addition of Zn2+. In the presence of 0.5 mM EGTA, only the parental strain was able to take up 65Zn2+. This high-affinity transport was energized by ATP. The genes were named znuACB (for zinc uptake; former name yebLMI ) and localized at 42 min on the genetic map of E. coli . At high Zn2+ concentrations, the znu mutants took up more 65Zn2+ than the parental strain. The high-affinity 65Zn2+ uptake was repressed by growth in the presence of 10 μM Zn2+. A znuA–lacZ operon fusion was repressed by 5 μM Zn2+ and showed a more than 20-fold increase in β-galactosidase activity when Zn2+ was bound to 1.5 μM TPEN [tetrakis-(2-pyridylmethyl) ethylenediamine]. To identify the Zn2+-dependent regulator, constitutive mutants were isolated and tested for complementation by a gene bank of E. coli . A complementing gene, yjbK of the E. coli genome, was identified and named zur (for zinc uptake regulation). The Zur protein showed 27% sequence identity with the iron regulator Fur. High-affinity 65Zn2+ transport of the constitutive zur mutant was 10-fold higher than that of the uninduced parental strain. An in vivo titration assay suggested that Zur binds to the bidirectional promoter region of znuA and znuCB .  相似文献   

7.
The effect of hydrogen peroxide on spores of Clostridium perfringens   总被引:3,自引:2,他引:1  
Dithiothreitol (DTT)-treated spores of Clostridium perfringens were much more sensitive to lysis by H2O2 in the presence of Cu2+ than untreated spores. Lysis was greatly inhibited by hydroxyl radical (.OH) scavengers such as thiourea, dimethylthiourea and dimethylsulfoxide, suggesting that lysis of spores by H2O2 involves formation of OH by Cu2+-catalysed decomposition of the peroxide. DTT-treated spores took up Cu2+ at almost the same rate and extent as did isolated cortical fragments. Hydrogen peroxide caused both the decrease in optical density and the hexosamine solubilization of cortical fragments which bound Cu2+.  相似文献   

8.
Copper (Cu)-polluted and unpolluted soils were used to study the effect of initial pollution on soil biological resistance and resilience by measuring the responses to perturbation using different parameters. Microbial biomass carbon, substrate-induced respiration and copy numbers of 16S rRNA gene were grouped as general parameters, while potential ammonia oxidation rate and copy numbers of amo A gene were grouped as specific functions. In addition, to illustrate how initial pollution affects soil biological resistance and resilience following secondary perturbation, the microbial community structure, together with free Cu2+ activities ([Cu2+]) in soil pore water and soil pH were also measured after secondary perturbation. Results showed that general parameters were more stable than specific ones. High [Cu2+] and low pH in soil pore water induced by Cu addition may lead to apparently low resistance and resilience, whereas the formation of a tolerant community after Cu pollution, secondary perturbation and Cu aging may contribute to resistance and resilience. Analysis of the phospholipid fatty acids profile showed that microbial community structure shifted along with the [Cu2+] gradient. The microbial community structure of the control soil was both resistant and resilient to 400 mg kg−1 Cu perturbation, whereas other treatments were neither resistant nor resilient.  相似文献   

9.
Six-month-old water cultures of Pinus radiataI D. Don seedlings showed optimal growth, and the highest CO2 assimilation and photosystem I-dependent ascorbate/dichlorophenolindophenol → NADP+ electron flow, at 3.0 uM Cu2+ (excess) in the hydroponic media. In the nine-month-old water cultures, when the early Cu deprivation has been overcome, the optimum for plant growth and CO2 fixation shifts to 0.3 u M Cu2+ (normal); at that time, the 3.0 uM Cu2+ water cultures showed toxic symptoms of foliar chlorosis. Under Cu2+ deficient levels (0.03 uM) a clear decrease in the photosystem I-linked electron transport and CO2 assimilation rates, as well as in the whole plant development, could be observed. Both six- and nine-month-old water cultures showed a close relationship between the Cu2+ concentration of the media and the foliar Cu content. However, leaf chlorophyll and the Cu content of thylakoid lamellae showed such a correlation only in the Cu2+ deficient and Cu2+ normal water cultures. The conclusion from these results is that the electron transport rate ascorbate/dicblorophenolindophenol → NADP+, and the Cu content of the photosynthetic membranes, can be used to diagnose a Cu deficiency in Pinus radiata plants.  相似文献   

10.
Abstract Pseudomonas syringae cells were exposed to Cu2+ alone or in the precence of acetate, proline or cysteine, at concentrations that reduced free Cu2+ to 1/10 of the total copper. Ligand concentrations (designated as isoeffective) were determined experimentally using a Cu2+-selective electrode and confirmed by computer calculations using published stability constants. Exposure of P. syringae cells to Cu2+ alone resulted in rapid and pronounced cell death, and binding of most of the copper in solution. The addition of acetate, proline or cysteine, a few minutes after Cu2+ treatment, resulted in a significant reduction in cell death, and in the amount of copper bound to the cells. For short exposures to Cu2+, cysteine was more effective than acetate or proline, but after 60 min of treatment, similar results were observed with these ligands. The addition of ligands before Cu2+ resulted in even more reduced copper toxicity. The results showed that, at isoeffective concentrations, weak and moderate copper-ligands can effectively antagonize copper toxicity, and that this protective effect does not require previously equilibrated copper-ligand solutions and is not very dependent of the nature of the ligand.  相似文献   

11.
The activities of 5'-methylthioadenosine (MTA) nucleosidase (EC 2.2.2.28) and 5-methylthioribose (MTR) kinase (EC 2.7.1.100) were related to changes in ethylene biosynthesis in tomato ( Lycopersicon esculentum Mill. cv. Rutgers) and cucumber ( Cucumis sativus Mill. cv. Poinsett 76) fruit following wounding and chemically induced stresses. Stress ethylene formation in wounded tomato and cucumber tissue continued to increase after wounding, reached its peak by 3h, and then declined. The activities of MTA nucleosidase and MTR kinase increased parallel to stress ethylene in both tissues. At peak ethylene formation, MTA and MTR kinase activities were 2- to 4-fold higher in wounded than in intact tissue. Wounded, mature-green tomato tissue treated with specific inhibitors of MTA nucleosidase and MTR kinase showed a significant reduction in the activities of these enzymes, which was concomitant with a decline in stress ethylene biosynthesis. When mature-green tomato discs were infiltrated with [14CH3] MTA and wounded, radioactive MTR and methionine were formed. Incubation of mature-green tomato discs with Cu2+ and Li+ in the presence of kinetin increased ethylene biosynthesis. MTA nucleosidase activity was higher than that of the control in the presence of Cu2+ but not in the presence of Li+, while MTR kinase activity was lower than that of the control in both Cu2+ and Li+ treatments. Data indicate that MTA nucleosidase and MTR kinase are required for wound-induced ethylene biosynthesis but not for chemical stress-induced ethylene by Cu2+ or Li+ treatments.  相似文献   

12.
Dehydrins are hydrophilic proteins that accumulate during embryogenesis and osmotic stress responses in plants. Here, we report an interaction between citrus dehydrin Citrus unshiu cold-regulated 15 kDa protein (CuCOR15) and DNA. Binding of CuCOR15 to DNA was detected by an electrophoretic mobility shift assay, a filter-binding assay and Southwestern blotting. The binding was stimulated by physiological concentrations of Zn2+, but little stimulation occurred when other divalent cations, such as Mg2+, Ca2+, Mn2+, Ni2+ and Cu2+, were substituted for Zn2+. Ethylenediaminetetraacetic acid cancelled the Zn2+-stimulated binding. A binding curve and competitor experiments suggested that the DNA binding of CuCOR15 exhibited low affinity and non-specificity. Moreover, tRNA competed with the DNA binding. Histidine-rich domains and a polylysine segment-containing domain participated in the DNA binding. These results suggest that CuCOR15 can interact with DNA, and also RNA, in the presence of Zn2+. Dehydrin may protect nucleic acids in plant cells during seed maturation and stress responses.  相似文献   

13.
Abstract: Nations were found to inhibit the uptake of L-tryptophan into synaptosomes with a shallow dose-response curve. Almost maximal inhibition was obtained with 10 mM-Na+. The divalent cations Ca2+ and Mg2+ were shown to be responsible for the increased uptake of L-tryptophan in the absence of Na+ ions. Other divalent cations also promoted tryptophan uptake under this condition (Ca2+ < Mg2+ < Mn2+ < Fe2+ < Zn2+ < Cu2+). It was concluded that monovalent chelate complexes were responsible for this enhancing effect. The measured L-tryptophan uptake was the net product of membrane bound and unbound tryptophan. Both bound and unbound tryptophan were increased in the presence of divalent cations. If no divalent cations were added to the incubation medium, Na+ ions decreased the unbound tryptophan but were without effect on bound tryptophan. Under these circumstances D-tryptophan had no effect on binding of the L-isomer and affected the transport of 1.-tryptophan only at very high does (100 x conc. L-tryptophan). These results suggest that I -tryptophan binds to a stereospecific transport carrier located in the synaptosomal membrane and that Na+ ions prevent the translocation of this carrier amino acid complex from the outer to the inner site of the neuronal membrane.  相似文献   

14.
Abstract: The activities mediated by the N -methyl-D-aspartate (NMDA) receptor were studied in cultured rat cerebellar granule cells. Micromolar concentrations of the metal binding compounds, EDTA, cysteine, and histidine, as well as serum albumin strongly potentiated receptor activity in the presence of millimolar concentrations of Ca2+ and Mg2+. The findings indicated that these agents remove an endogenous metal, probably Zn2+, which attenuates NMDA receptor-mediated 45Ca uptake and toxicity. Several added metal ions were therefore tested at low micromolar concentrations. Zn2+ was found to be the most potent inhibitor of NMDA-induced 45Ca uptake, followed by Cu2+ and Fe2+. Co2+, Cd2+, Fe3+, and AI3+ had no significant effect, whereas Ni2+ potentiated the 45Ca uptake but inhibited at much higher concentrations. The potentiating agents that remove the endogenous metal had a particularly dramatic effect in the presence of Mg2+, the voltage-dependent suppressor of the NMDA receptor. Mg2+ also played an important role in the inhibitory effect of added Zn2+. Much lower concentrations of Zn2+ were needed to achieve inhibition of NMDA-induced 45Ca uptake in the presence of Mg2+. Under a variety of conditions, a very good correlation was found between NMDA receptor-mediated 45Ca uptake and the magnitude of acute neurotoxicity.  相似文献   

15.
Wet mass and water content of four lots of whole eggs did not change throughout embryonic development of rainbow trout Oncorhynchus mykiss. Eggs in all four lots accumulated Na+. Eggs in lots 2 and 4 also accumulated Ca2+ and Cl-, whereas eggs in lot 1 showed no significant change in Ca2+ or Cl- and eggs in lot 3 showed no change in Cl-and a small loss of Ca2+. Although the Na+ content of embryonic tissues increases in the later stages of development, the yolk sac content remained constant, indicating uptake of Na+ from the environment. Na+ uptake by whole eggs was non-saturable, consistent with diffusion of Na+ across the chorion into the perivitelline fluid. Na+ uptake in dechorionated embryos was saturable, as was Ca2+ uptake by both whole eggs and dechorionated embryos, consistent with active uptake or facilitated diffusion mechanisms at the surface of embryos. Very low Ca2+ uptake rates in dechorionated embryos suggest that the Ca2+ uptake mechanism is not fully developed until after hatching.  相似文献   

16.
Mechanism of copper-enhanced photoinhibition in thylakoid membranes   总被引:2,自引:0,他引:2  
The effect of copper on photoinhibition of photosystem II (PSII) in vitro was studied in bean ( Phaseolus vulgaris L. cv. Dufrix) and pumpkin ( Cucurbita pepo L.) thylakoids. The thylakoids were illuminated at 200–2 000 μmol photons m−2 s−1 in the presence of 70–1 830 added Cu2+ ions per PSII. Three lines of evidence show that the irreversible damage of PSII caused by illumination of thylakoids in the presence of Cu2+ was mainly due to donor-side photoinhibition resulting from inhibition of the PSII donor side by Cu2+. First, addition of an artificial electron donor partially restored PSII activity of thylakoids that had been illuminated in the presence of Cu2+. Second, already moderate light was enough to cause rapid inhibition of PSII, and the inhibition could be saturated by light. Third, the extrinsic polypeptides of the oxygen-evolving complex were found to become oxidized by the combined effect of Cu2+ and light. The presence of oxygen was not necessary for the copper-induced enhancement of photoinhibition of PSII. When the illumination was prolonged, copper caused a gradual collapse of the thylakoid structure by increasing degradation of thylakoid proteins.  相似文献   

17.
Aim:  The capacities of live and heat-killed cells of Saccharomyces cerevisiae at 45°C for the removal of copper, nickel and zinc from the solution were compared.
Methods and Results:  Kinetic studies have shown a maximum accumulation of Ni2+ and Zn2+ after 10 min for both types of cells, while for Cu2+ this was attained after 30 and 60 min for dead and live cells, respectively. Equilibrium studies have shown that inactivated biomass displayed a greater Zn2+ and Ni2+ accumulation than live yeasts. For Cu2+, live and dead cells showed similar accumulation. Fluorescence, scanning electron microscopy and infrared spectroscopy studies have shown that no appreciable structural or molecular changes occurred in the cells during the killing process. The increased metal uptake observed in dead cells can be most likely explained by the loss of membrane integrity, which allows the exposition of further metal-binding sites present inside the cells.
Conclusions:  Heat-killed cells showed a higher degree of heavy metal removal than live cells, being more suitable for further bioremediation works.
Significance and Impact of the Study:  Dead flocculent cells can be used in a low cost technology for detoxifying metal-bearing effluents as this approach combines an efficient metal removal with the ease of cell separation.  相似文献   

18.
Abstract: Zn2+-glycerophosphocholine cholinephosphodiesterase, responsible for the conversion of glycerophosphocholine into glycerol and phosphocholine, was inactivated during incubation with ascorbic acid at 38°C. The inclusion of copper ions or Fe2+ accelerated the ascorbate-induced inactivation, with Cu2+ or Cu+ being much more effective than Fe2+, suggestive of ascorbate-mediated oxidation. Dehydroascorbic acid had no effect on the phosphodiesterase, but H2O2 inactivated the enzyme in a concentration-dependent manner. Also, the enzyme was inactivated partially by a superoxide anion-generating system but not an HOCl generator. In support of involvement of H2O2 in the ascorbate action, catalase and superoxide dismutase expressed a complete and a partial protection, respectively. However, hydroxy radical scavengers such as mannitol, benzoate, or dimethyl sulfoxide were incapable of preventing the ascorbate action, excluding the participation of extraneous OH. Although p -nitrophenylphosphocholine exhibited a modest protection against the ascorbate action, a remarkable protection was expressed by amino acids, especially by histidine. In addition, imidazole, an electron donor, showed a partial protection. Separately, when Cu2+-induced inactivation of the phosphodiesterase was compared with the ascorbate-mediated one, the protection and pH studies indicate that the mechanism for the ascorbate action is different from that for the Cu2+ action. Here, it is proposed that Zn2+-glycerophosphocholine cholinephosphodiesterase is one of brain membrane proteins susceptible to oxidative inactivation.  相似文献   

19.
Growth inhibition of the green alga Dunalietla parva Lerche has been observed during cultivation in low Cu2+ media. A minimum endogenous Cu concentration for unrestricted growth of 100 to 200 nmol ml−1 packed cell volume was estimated. At lower concentrations, Cu deficiency causes a decrease in photosynthesis and respiration. Assay of photosynthetic electron transport rates as well as the determination of several redox components showed that the target of Cu deprivation in the photosynthetic apparatus is the synthesis of Cu-containing plastocyanin. Consequently, inhibited formation of plastocyanin resulted in low activities of photosynthetic electron transport. A secondary, indirect effect of Cu deficiency is the reduction of thylakoid formation resulting in an additional decrease of photosynthesis compared to cultures with sufficient Cu2+.
The inhibitory influence of low Cu2+ on respiration was located at the site of cytochrome oxidase. In contrast to blue-green algae, a strong coordination of the biosynthesis of the cytochrome oxidase complex was evident. During restricted Cu2+ supply the formation of cytochiome aa3 , another component besides Cu, was stalled. The resulting low activities of cytochrome oxidase are responsible for decreased respiratory electron transfer activity from NADPH to oxygen. At Cu2+ concentrations which exert only moderate effects on Dunalietla , the cytochrome oxidase reaction was more strongly affected than the photosystem I reaction.  相似文献   

20.
The mechanism of cobalt uptake was investigated using cells of the giant alga Chara corallina in which it is possible to resolve separately uptake by the cell wall and actual influx across the cell membrane. The absorption of 60Co by Chara cells appeared to saturate within 2 h, but this was mainly due to rapid uptake into the cell wall which accounted for 87–92% of the total activity. Even after prolonged desorption most of the cell‐associated 60Co was found on the cell wall. The intracellular distribution of absorbed 60Co was investigated by fractionating the cell into cytoplasm and vacuole. It was shown that 60Co influx to the vacuole occurs simultaneously with influx to the cytoplasm. The transported species appears to be Co2+ rather than the less charged Co(OH)+ or Co(OH)2. 60Co influx is pH dependent (optimum pH 7–9), and is sensitive to some other divalent metals. Influx from solutions containing 1 µ M 60Co was inhibited by 5 µ M Cd2+, Cu2+, and Zn2+, but Mn2+ and Ni2+ had no significant effect. The sensitivity of Co uptake to N ‐ethyl maleimide (NEM) and cysteine suggests that the transport system involves direct binding of CO2+ to ‐SH groups.  相似文献   

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