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1.
Here we present a Zn transporter cDNA named MtZIP2 from the model legume Medicago truncatula. MtZIP2 encodes a putative 37 kDa protein with 8-membrane spanning domains and has moderate amino acid identity with the Arabidopsis thaliana Zn transporter AtZIP2p. MtZIP2 complemented a Zn-uptake mutant of yeast implying that the protein encoded by this gene can transport Zn across the yeast's plasma membrane. The product of a MtZIP2-GFP fusion construct introduced into onion cells by particle bombardment likewise localized to the plasma membrane. The MtZIP2 gene was expressed in roots and stems, but not in leaves of M. truncatula and, in contrast to all other plant Zn transporters characterized thus far, MtZIP2 was up-regulated in roots by Zn fertilization. Expression was highest in roots exposed to a toxic level of Zn. MtZIP2 expression was also examined in the roots of M. truncatula when colonized by the obligate plant symbiont, arbuscular mycorrhizal (AM) fungi, since AM fungi are renowned for their ability to supply plants with mineral nutrients, including Zn. Expression was down-regulated in the roots of the mycorrhizal plants and was associated with a reduced level of Zn within the host plant tissues. 相似文献
2.
Christopher A. Dieni Kenneth B. Storey 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2010,180(8):1133-1142
Glucose-6-phosphate dehydrogenase (G6PDH) and the pentose phosphate pathway play a key role in reductive biosynthesis and
antioxidant defense, while diverting glucose from other cellular functions. G6PDH was isolated from liver of the wood frog,
Rana sylvatica, a freeze tolerant species that uses glucose as a cryoprotectant. Analysis of kinetic parameters (K
m and V
max) of G6PDH showed a significant increase in K
m G6P (from 98.2 ± 3.8 to 121 ± 5.3 μM) and K
m NADP+ (from 65.5 ± 2.3 to 89.1 ± 4.8 μM) in frogs following freezing exposure, indicating lower affinity for G6PDH substrates in
this state. Subsequent analyses indicated that differential phosphorylation of G6PDH between the two states was responsible
for the altered kinetic properties. Thus, two differentially charged forms of G6PDH were resolved by DEAE ion-exchange chromatography
and, compared with controls, the proportion of G6PDH activity in peak I decreased and in peak II increased in liver from frozen
frogs. G6PDH in peak I had a K
m G6P of 94.1 ± 1.1 μM and K
m NADP+ of 61.2 ± 3.5 μM, whereas Peak II G6PDH showed higher values (K
m G6P was 172 ± 4.3 μM, K
m NADP+ was 98.2 ± 3.3 μM). G6PDH from each peak was incubated with ions and second messengers to stimulate the actions of protein
kinases with results indicating that G6PDH can be phosphorylated by protein kinase G, protein kinase C, AMP-activated protein
kinase, or calmodulin-dependent protein kinase. The data indicate that in control frogs, G6PDH is in a high phosphate form
and displays a high substrate affinity, whereas in frozen frogs G6PDH is less phosphorylated, with lower substrate affinity. 相似文献
3.
1-Naphthol 2-hydroxylase (1-NH) which catalyzes the conversion of 1-naphthol to 1,2-dihydroxynaphthalene was purified to homogeneity
from carbaryl-degrading Pseudomonas sp. strain C6. The enzyme was found to be a homodimer with subunit molecular weight of 66 kDa. UV, visible and fluorescence
spectral properties, identification of flavin moiety by HPLC as FAD, and reconstitution of apoenzyme by FAD suggest that enzyme
is FAD-dependent. 1-NH accepts electron from NADH as well as NADPH. Besides 1-naphthol (K
m, 9.1 μM), the enzyme also accepts 5-amino 1-naphthol (K
m, 6.4 μM) and 4-chloro 1-naphthol (K
m, 2.3 μM) as substrates. Enzyme showed substrate inhibition phenomenon at high concentration of 1-naphthol (K
i, 283 μM). Stoichiometric consumption of oxygen and NADH, and biochemical properties suggest that 1-NH belongs to FAD containing
external flavomonooxygenase group of oxido-reductase class of enzymes. Based on biochemical and kinetic properties, 1-NH from
Pseudomonas sp. strain C6 appears to be different than that reported earlier from Pseudomonas sp. strain C4. Chemical modification and protection by 1-naphthol and NADH suggest that His, Arg, Cys, Tyr and Trp are at
or near the active site of 1-NH. 相似文献
4.
5.
Sunita R. Nadella Carrie C. Y. Hung Chris M. Wood 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(1):27-41
An in vitro gut-sac technique and 64Cu as a radiotracer were used to characterize gastric copper (Cu) transport. Cu transport was stimulated by low luminal pH
(4.0 vs. 7.4), to a greater extent than explained by the increased availability of the free Cu2+ ion. At pH = 4.0, uptake kinetics were indicative of a low affinity (K
m = 525 μmol L−1), saturable carrier-mediated component superimposed on a large linear (diffusive and/or convective) component, with about
50% occurring by each pathway at Cu = 50 μmol L−1. Osmotic gradient experiments showed that solvent drag via fluid transport may play a role in Cu uptake via the stomach,
in contrast to the intestine. Also unlike the intestine, neither the Na+ gradient, high Ag, nor phenamil had any influence on gastric Cu transport, and a tenfold excess of Fe and Zn failed to inhibit
Cu uptake. These findings indicate that neither Na+-dependent pathways nor DMT1 are likely candidates for carrier-mediated Cu transport in the stomach. We have cloned a partial
cDNA sequence for the copper transporter Ctr1, and show its mRNA expression in all segments of the trout gastrointestinal tract, including the stomach. Based on the fact
that this transporter is functional at low pH conventionally found in the stomach lumen, we suggest Ctr1 is a pathway for gastric Cu transport in trout. Extreme hypoxia inhibited Cu uptake. High
P\textCO2 P_{{{\text{CO}}_{2} }} levels (7.5 torr) increased Cu uptake and acetazolamide (100 μmol L−1) significantly inhibited Cu uptake, indicating carbonic anhydrase activity was involved in gastric Cu transport. Transport of Cu was insensitive to bafilomycin (10 μmol L−1) suggesting a V-ATPase did not play a direct role in the process. Expression (mRNA) of H
+
, K
+-ATPase, carbonic anhydrase 2, and the α-3 isoform of Na
+–K
+-ATPase were observed in the stomach. We suggest these enzymes facilitate Cu transport in the stomach indirectly as part of a physiological
mechanism exporting H+ to the cell exterior. However, pre-treatment with the H
+
, K
+-ATPase proton pump blocker omeprazole did not affect gastric Cu transport, suggesting that other mechanisms must also be involved. 相似文献
6.
Effects of zinc (12–180 μM) alone and in mixtures with 12 μM Cd on metal accumulation, dry masses of roots and shoots, root
respiration rate, variable to maximum fluorescence ratio (FV/FM), and content of photosynthetic pigments were studied in hydroponically cultivated chamomile (Matricaria recutita) plants. The content of Zn in roots and shoots increased with the increasing external Zn concentration and its accumulation
in the roots was higher than that in the shoots. While at lower Zn concentrations (12 and 60 μM) the presence of 12 μM Cd
decreased Zn accumulation in the roots, treatment with 120 and 180 μM Zn together with 12 μM Cd caused enhancement of Zn content
in the root. Presence of Zn (12–120 μM) decreased Cd accumulation in roots. On the other hand, Cd content in the shoots of
plants treated with Zn + Cd exceeded that in the plants treated only with 12 μM Cd. Only higher Zn concentrations (120 and
180 μM) and Zn + Cd mixtures negatively influenced dry mass, chlorophyll (Chl) and carotenoid content, FV/FM and root respiration rate. Chl b was reduced to a higher extent than Chl a. 相似文献
7.
Nzengue Y Steiman R Rachidi W Favier A Guiraud P 《Biological trace element research》2012,146(3):410-419
In this report, we have investigated the role of copper (Cu) and zinc (Zn) in oxidative stress induced by cadmium (Cd) in
C6 cells. Cells were exposed to 20 μM Cd, 500 μM Cu, and 450 μM Zn for 24 h. Then, toxic effects, cellular metals levels,
oxidative stress parameters, cell death, as well as DNA damage were evaluated. Cd induced an increase in cellular Cd, Cu,
and Zn levels. This results not only in the inhibition of GSH-Px, GRase, CAT, and SOD activities but also in ROS overproduction,
oxidative damage, and apoptotic cell death not related to Cu and Zn mechanisms. The thiol groups and GSH levels decreased,
whereas the lipid peroxidation and DNA damage increased. The toxicity of Zn results from the imbalance between the inhibition
of antioxidant activities and the induction of MT synthesis. The increase in Cu and Zn levels could be explained by the disruption
of specific transporter activities, Cd interference with signaling pathways, and metal displacement. Our results suggest that
the alteration of Cu and Zn homeostasis is involved in the oxidative stress induced by Cd. 相似文献
8.
Hana Nůsková Marek Vrbacký Zdeněk Drahota Josef Houštěk 《Journal of bioenergetics and biomembranes》2010,42(5):395-403
The mechanism of cyanide’s inhibitory effect on the mitochondrial cytochrome c oxidase (COX) as well as the conditions for its recovery have not yet been fully explained. We investigated three parameters
of COX function, namely electron transport (oxygen consumption), proton transport (mitochondrial membrane potential Δψ
m) and the enzyme affinity to oxygen (p
50
value) with regard to the inhibition by KCN and its reversal by pyruvate. 250 μM KCN completely inhibited both the electron
and proton transport function of COX. The inhibition was reversible as demonstrated by washing of mitochondria. The addition
of 60 mM pyruvate induced the maximal recovery of both parameters to 60–80% of the original values. When using low KCN concentrations
of up to 5 μM, we observed a profound, 30-fold decrease of COX affinity for oxygen. Again, this decrease was completely reversed
by washing mitochondria while pyruvate induced only a partial, yet significant recovery of oxygen affinity. Our results demonstrate
that the inhibition of COX by cyanide is reversible and that the potential of pyruvate as a cyanide poisoning antidote is
limited. Importantly, we also showed that the COX affinity for oxygen is the most sensitive indicator of cyanide toxic effects. 相似文献
9.
Diaphanosoma brachyurum (Cladocera: Sididae) is a common limnetic species in summer-temperate and tropical water bodies. Few studies have investigated
the sensitivity of D. brachyurum to toxic chemicals despite this species often being dominant in natural lakes and ponds. We performed acute toxicity tests
of three heavy metals, copper (Cu), zinc (Zn), and cadmium (Cd), to D. brachyurum. For D. brachyurum, the lethal concentration (LC)50 values of Cu (24-h LC50 = 16.4 μg/L, 48-h LC50 = 10.4 μg/L) and Zn (24-h LC50 = 253.4 μg/L, 48-h LC50 = 174.1 μg/L) were lower than those for D. magna, one of the most used test organisms for toxic chemicals. On the other hand, for D. brachyurum the 24-h LC50 of Cd (166.4 μg/L) was much greater than that for D. magna, and the 48-h LC50 of Cd (69.8 μg/L) was comparable. Our results indicate that D. brachyurum may be more strongly influenced by Zn and Cu than is D. magna. It is likely that the summer plankton community in which Diaphanosoma species is dominant is more sensitive to heavy metals than a community in which Daphnia species are dominant. 相似文献
10.
Copper, Cd and Zn can be found at elevated concentrations in contaminated estuarine and coastal waters and have potential
toxic effects on phytoplankton species. In this study, the effects of these metals on the intracellular production of the
polypeptides phytochelatin and glutathione by the marine diatom Phaeodactylum tricornutum were examined in laboratory cultures. Single additions of Cu and Cd (0.4 μM Cu2 and 0.45 μM Cd2+) to the culture medium induced the production of short-chained phytochelatins ((γ-Glu-Cys)n-Gly where n = 2–5), whereas a single addition of Zn (2.2 μM Zn2+) did not stimulate phytochelatin production. Combination of Zn with Cu resulted in a similar phytochelatin production compared
with a single Cu addition. The simultaneous exposure to Zn and Cd led to an antagonistic effect on phytochelatin production,
which was probably caused by metal competition for cellular binding sites. Glutathione concentrations were affected only upon
exposure to Cd (85% increase) or the combination of Cd with Zn (65% decrease), relative to the control experiment. Ratios
of phytochelatins to glutathione indicated a pronounced metal stress in response to exposures to Cu or Cd combined with Zn.
This study indicates that variabilities in phytochelatin and glutathione production in the field can be explained in part
by metal competition for cellular binding sites. 相似文献
11.
OATP1B1 and 1B3 are related transporters mediating uptake of numerous compounds into hepatocytes. A putative model of OATP1B3
with a “positive binding pocket” containing conserved positively charged amino acids was predicted (Meier-Abt et al. J Membr
Biol 208:213–227, 2005). Based on this model, we tested the hypothesis that these positive amino acids are important for OATP1B1
function. We made mutants and measured surface expression and uptake of estradiol-17β-glucuronide, estrone-3-sulfate and bromosulfophthalein
in HEK293 cells. Two of the mutants had low surface expression levels: R181K at 10% and R580A at 30% of wild-type OATP1B1.
A lysine at position 580 (R580K) rescued the expression of R580A. Mutations of several amino acids resulted in substrate-dependent
effects. The largest changes were seen for estradiol-17β-glucuronide, while estrone-3-sulfate and bromosulfophthalein transport
were less affected. The wild-type OATP1B1 K
m value for estradiol-17β-glucuronide of 5.35 ± 0.54 μM was increased by R57A to 30.5 ± 3.64 μM and decreased by R580K to 0.52 ± 0.18 μM.
For estrone-3-sulfate the wild-type high-affinity K
m value of 0.55 ± 0.12 μM was increased by K361R to 1.8 ± 0.47 μM and decreased by R580K to 0.1 ± 0.04 μM. In addition, R580K
reduced the V
max values for all three substrates to <25% of wild-type OATP1B1. Mutations at intracellular K90, H92 and R93 mainly affected
V
max values for estradiol-17β-glucuronide uptake. In conclusion, the conserved amino acids R57, K361 and R580 seem to be part
of the substrate binding sites and/or translocation pathways in OATP1B1. 相似文献
12.
Growth of three strains of Tetracladium marchalianum was inhibited by Cd-, and, to a lesser extent, by Cu-and Zn-chloride. In the presence of 50 μM Cd(II), all strains increased
total thiol and glutathione production to 6, 11, and 21 μmoles · mg−1 dry mass, respectively. Cd(II) also induced the synthesis of one to several compounds reacting with 5,5′-dithio-bis-(2-nitrobenzoic
acid). In order to identify buffer-soluble thiolic compounds other than cysteine, γ-EC and γ-ECG (glutathione) were analyzed
and confirmed by mass spectrometry. No water soluble sulfides were detectable in any of the culture filtrates, but Cd(II)
exposure at a concentration of 50 μM raised sulfide levels in the mycelia of two of the strains between 3 and 7-fold, Cu(II)
and Zn(II) had no effect. Energy Dispersive X-ray-analysis (EDX) and Electron Spectrometry-Images (ES-I) of one strain revealed
increased levels of Cu and Zn in the cytoplasm and even higher levels in vacuolar precipitates. Zn and Cu are accumulated
in the vacuoles as polyphosphates, identified by Electron Energy Loss-Spectrometry (EELS). Cd was found only in the vacuoles. 相似文献
13.
Ectoenzymatic Activity and Uptake of Monomers in Marine Bacterioplankton Described by a Biphasic Kinetic Model 总被引:4,自引:0,他引:4
Abstract
The kinetics of bacterial hydrolytic ectoenzymatic activity and the uptake of monomeric compounds were investigated in the
Northwestern Mediterranean Sea. Aminopeptidase and α- and β-glucosidase activities were analyzed by using fluorogenic substrates
at 15–22 concentrations ranging from 1 nM to 500 μM. Radiolabeled glucose and a mixture of amino acids were chosen as representatives
of monomeric compounds, and the bacterial uptake rates (assimilation plus respiration) were determined over a wide range of
substrate concentrations (from 0.2 nM to 3 μM). We found biphasic kinetics both for hydrolytic enzymes and uptake systems:
high affinity enzymes at low concentrations of substrates (K
m values ranged from 48 nM to 2.7 μM for ectoenzymes and from 1.4 nM to 42 nM for uptake systems), and low affinity enzymes
at high concentrations of substrates (K
m values ranged from 18 μM to 142 μM for ectoenzymes and from 0.1 μM to 1.3 μM for uptake systems). Transition between high
and low affinity enzymes was observed at 10 μM for aminopeptidase and from 1 μM to 25 μM for glucosidases, and it was more
variable and less pronounced for the uptake of glucose (40 nM–0.28 μM) and amino acids (10 nM–0.16 μM). Results showed that
the potential rates of hydrolysis and uptake are tightly coupled only if the high affinity hydrolytic ectoenzymes and the
low affinity uptake systems are operating simultaneously.
Received: 5 March 1998; Accepted: 31 July 1998 相似文献
14.
Effects of zinc ex vivo and intracellular zinc chelator in vivo on taurine uptake in goldfish retina
Taurine and zinc exert neurotrophic effects. Zinc modulates Na+/Cl−-dependent transporters. This study examined the effect of zinc (ZnSO4) ex vivo and zinc chelator N,N,N′,N′-tetrakis-(2-pyridylmethyl) ethylenediamine (TPEN) in vivo on [3H]taurine transport in goldfish retina. The effect of TPEN in vivo on taurine and zinc levels was determined. Isolated cells
were incubated in Ringer with zinc (0.1–100 μM). Taurine transport was done with taurine (0.001–1 mM) and 50 nM [3H]taurine. Zinc (100 μM) noncompetitively inhibited taurine transport. TPEN was administered intraocularly and retinas extracted
3, 5 and 10 days later. Taurine was determined by HPLC (nmol/mg protein) and zinc by spectrophotometry ICP (mg/mg protein).
Taurine and zinc levels decreased at 3 days and increased at 10 days after TPEN administration. At 10 days after intraocular
TPEN, taurine transport affinity increased (K
s = 0.018 ± 0.006 vs. 0.028 ± 0.008 mM). Apparently, zinc deficiency affects the taurine–zinc complex and taurine availability.
The increased taurine uptake affinity by TPEN was possibly associated with a response to maximize retinal taurine content
at low zinc concentration. 相似文献
15.
Mucosal crude microsomes, prepared from proximal rat small intestine, exhibited significant Mg-dependent, Zn-ATPase activity;
V
max
= 23 μmoles Pi/mg protein/hr, K
m
= 160 nm, and Hill Coefficient, n= 1.5. Partial purification (∼10-fold) was achieved by detergent extraction, and centrifugation through 250 mm sucrose: V
max
= 268 units, K
m
= 1 nm, and n= 6. In partially purified preparations, the assay was linear with time to 60 min, and with protein concentration to 1 μg/300
μl. Activities at pH 8 and 8.5 were higher than at pH 7.2. The ATP K
m
was 0.7 mm, with an optimal ATP/Mg ratio of ∼2. Ca elicited ATPase activity but did not augment the Zn-dependent activity. In partially
purified preparations, the homologous salts of Co, Cd, Cu, and Mn exhibited no detectable activity. Vanadate inhibition studies
yielded two component kinetics with a K
i
of 12 μm for the first component, and 96 μm for the second component, in partially purified preparations. Tissue distribution analyses revealed gradients of activity.
In the proximal half of the small intestine, Mg/Zn activity increased progressively from crypt to villus tip. In long axis
studies, this activity decreased progressively from proximal to distal small bowel.
Received: 12 September 2000/Revised 6 January 2001 相似文献
16.
Summary. Spermine is taken up by Ehrlich ascites tumour cells through a specific, saturable, temperature and energy-dependent transport
system with a remarkably low affinity constant for spermine (around 1 μM). In the absence of a potassium ion gradient through the plasma membrane, spermine uptake remains saturable but the value
of the Km for spermine is much higher (153 μM). Difluormethylornithine treatment (3 mM for 48 h) induces significant increases in Vmax values (up to 9-fold) and changes in the Km values with scarce statistical significance. Among the biogenic amines tested, only spermidine and, partly, agmatine seem
to share the same transport system with spermine. No difference is observed in the rate of spermine transport when assays
are carried out in the presence of 50-fold excess of ornithine or calcium, or 100-fold excess of glutamine.
Received April 25, 2000 Accepted November 1, 2000 相似文献
17.
Three fenamates—niflumic, flufenamic and mefenamic acids—were tested for effects on substrate-induced currents of glutamate
and glycine transporters (EAAT1, EAAT2, GLYT1b and GLYT2a) expressed in Xenopus laevis oocytes. All fenamates inhibited EAAT1 currents; 100 μM flufenamic acid produced the most inhibition, decreasing the I
max by 53 ± 4% (P < 0.001). EAAT2 currents were less sensitive, but 100 μM flufenamic acid inhibited the I
max by 34 ± 5% (P = 0.006). All fenamates inhibited GLYT1b currents; 100 μM flufenamic acid produced the most inhibition, decreasing the I
max by 61 ± 1% (P < 0.001). At 100 μM, effects on the GLYT2a I
max were mixed: 13 ± 2% inhibition by flufenamic acid (P = 0.002), 30 ± 6% enhancement by niflumic acid (P = 0.002), and no effect by mefenamic acid. Minor effects on substrate affinity suggested non-competitive mechanisms. These
data could contribute to the development of selective transport modulators. 相似文献
18.
M. G. Sá G. A. Ahearn F. P. Zanotto 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(5):605-615
Gills are the first site of impact by metal ions in contaminated waters. Work on whole gill cells and metal uptake has not
been reported before in crustaceans. In this study, gill filaments of the American lobster, Homarus americanus, were dissociated in physiological saline and separated into several cell types on a 30, 40, 50, and 80% sucrose gradient.
Cells from each sucrose solution were separately resuspended in physiological saline and incubated in 65Zn2+ in order to assess the nature of metal uptake by each cell type. Characteristics of zinc accumulation by each kind of cell
were investigated in the presence and absence of 10 mM calcium, variable NaCl concentrations and pH values, and 100 μM verapamil,
nifedipine, and the calcium ionophore A23187. 65Zn2+ influxes were hyperbolic functions of zinc concentration (1–1,000 μM) and followed Michaelis–Menten kinetics. Calcium reduced
both apparent zinc binding affinity (K
m) and maximal transport velocity (J
max) for 30% sucrose cells, but doubled the apparent maximal transport velocity for 80% sucrose cells. Results suggest that calcium,
sodium, and protons enter gill epithelial cells by an endogenous broad-specificity cation channel and trans-stimulate metal
uptake by a plasma membrane carrier system. Differences in zinc transport observed between gill epithelial cell types appear
related to apparent affinity differences of the transporters in each kind of cell. Low affinity cells from 30% sucrose were
inhibited by calcium, while high affinity cells from 80% sucrose were stimulated. 65Zn2+ transport was also studied by isolated, intact, gill filament tips. These intact gill fragments generally displayed the same
transport properties as did cells from 80% sucrose and provided support for metal uptake processes being an apical phenomenon.
A working model for zinc transport by lobster gill cells is presented. 相似文献
19.
Tarasova MV Kuznetsov VV Netesova NA Gonchar DA Degtyarev SKh 《Biochemistry. Biokhimii?a》2010,75(12):1484-1490
A restriction-modification system from Bacillus psychrodurans AC (recognition sequence 5′-CCGC-3′) comprises two DNA methyltransferases: M1.BspACI and M2.BspACI. The bspACIM1 gene was cloned in the pJW2 vector and expressed in Escherichia coli cells. High-purity M1.BspACI preparation has been obtained by chromatography on different carriers. M1.BspACI has a temperature
optimum of 30°C and demonstrates maximum activity at pH 8.0. M1.BspACI modifies the first cytosine in the recognition sequence
5′-CCGC-3′. The kinetic parameters of M1.BspACI DNA methylation are as follows: K
m for phage λ DNA is 0.053 μM and K
m for S-adenosyl-L-methionine is 5.1 μM. The catalytic constant (k
cat) is 0.095 min−1. 相似文献
20.
A study was carried out to evaluate the sensitivity of different chlorophyll-a (chl-a) fluorescence parameters measured in freshwater biofilms as metal pollution biomarkers of short- and long-term metal exposures
at environmentally realistic concentrations. A microcosm experiment was performed using indoor channels. Mature biofilms were
exposed from hours to weeks to three different treatments: No-Metal, Zn (400 μg l−1); and Zn plus Cd (400 μg l−1 and 20 μg l−1, respectively). Metal concentration was based on a real case study: the Riou-Mort River (France). Biofilms exposed to Zn
bioaccumulated similar Zn contents per dry weight to those exposed to the mixture (Zn plus Cd) causing a similar inhibition
of the effective quantum yield
(\Upphi\textM¢)(\Upphi_{\text{M}}^{\prime}) during the first hours of exposure. A reduction of the algal biomass, a shift in the community composition (a high reduction
of diatoms), a reduction of the maximal quantum yield (ΦM) and a strong reduction of non-photochemical quenching (NPQ) were observed from day 14 until the end of the experiment (35 days).
The results indicate that the effects of the metal mixture present in the Riou-Mort on biofilms could be attributed to Zn
toxicity. The use of a set of chl-a fluorescence measurements, including photochemical and NPQ parameters, are recommended as a reliable biomarker tool box to
evaluate both short- and long-term effects of metals on biofilms containing oxygenic photoautotrophs, suggesting its use in
field applications. 相似文献