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1.
We report here that the Leishmania major ascorbate peroxidase (LmAPX), having similarity with plant ascorbate peroxidase, catalyzes the oxidation of suboptimal concentration of ascorbate to monodehydroascorbate (MDA) at physiological pH in the presence of added H2O2 with concurrent evolution of O2. This pseudocatalatic degradation of H2O2 to O2 is solely dependent on ascorbate and is blocked by a spin trap, α-phenyl-n-tert-butyl nitrone (PBN), indicating the involvement of free radical species in the reaction process. LmAPX thus appears to catalyze ascorbate oxidation by its peroxidase activity, first generating MDA and H2O with subsequent regeneration of ascorbate by the reduction of MDA with H2O2 evolving O2 through the intermediate formation of O2. Interestingly, both peroxidase and ascorbate-dependent pseudocatalatic activity of LmAPX are reversibly inhibited by SCN in a concentration dependent manner. Spectral studies indicate that ascorbate cannot reduce LmAPX compound II to the native enzyme in presence of SCN. Further kinetic studies indicate that SCN itself is not oxidized by LmAPX but inhibits both ascorbate and guaiacol oxidation, which suggests that SCN blocks initial peroxidase activity with ascorbate rather than subsequent nonenzymatic pseudocatalatic degradation of H2O2 to O2. Binding studies by optical difference spectroscopy indicate that SCN binds LmAPX (Kd = 100 ± 10 mM) near the heme edge. Thus, unlike mammalian peroxidases, SCN acts as an inhibitor for Leishmania peroxidase to block ascorbate oxidation and subsequent pseudocatalase activity.  相似文献   

2.
Catalase-peroxidases (KatGs) are unique bifunctional heme peroxidases that exhibit peroxidase and substantial catalase activities. Nevertheless, the reaction pathway of hydrogen peroxide dismutation, including the electronic structure of the redox intermediate that actually oxidizes H2O2, is not clearly defined. Several mutant proteins with diminished overall catalase but wild-type-like peroxidase activity have been described in the last years. However, understanding of decrease in overall catalatic activity needs discrimination between reduction and oxidation reactions of hydrogen peroxide. Here, by using sequential-mixing stopped-flow spectroscopy, we have investigated the kinetics of the transition of KatG compound I (produced by peroxoacetic acid) to its ferric state by trapping the latter as cyanide complex. Apparent bimolecular rate constants (pH 6.5, 20 °C) for wild-type KatG and the variants Trp122Phe (lacks KatG-typical distal adduct), Asp152Ser (controls substrate access to the heme cavity) and Glu253Gln (channel entrance) are reported to be 1.2 × 104 M− 1 s− 1, 30 M− 1 s− 1, 3.4 × 103 M− 1 s− 1, and 8.6 × 103 M− 1 s− 1, respectively. These findings are discussed with respect to steady-state kinetic data and proposed reaction mechanism(s) for KatG. Assets and drawbacks of the presented method are discussed.  相似文献   

3.
4.
Grapefruit is one of the most susceptible citrus genotypes to Asiatic Citrus Canker, caused by Xanthomonas axonopodis pv. citri (Xac), that can cause severe losses in citrus yield and quality. Although much is known about citrus response to Xac, little is known of the role of antioxidant metabolism. Grapefruit leaves were artificially injected with a strain of Xac obtained from a commercial grove in Florida and components of oxidative metabolism were measured. Symptoms observed included water soaking (2 dai; days after inoculation), raised and ruptured epidermis (6-8 dai), formation of necrotic lesions (16 dai), and leaf abscission (21 dai). The Xac population increased to a maximum (≈109 CFU/cm2) 8 dai and then declined to ≈107 CFU/cm2 by 20 dai. Lipid peroxidation was higher in infected leaves than uninoculated controls from 4 to 21 dai indicating greater oxidative stress. H2O2 concentration demonstrated a biphasic pattern with peak concentrations at 4 and 13 dai and minimum concentrations that were lower than the controls at 10 and 20 dai. The H2O2 concentration somewhat corresponded with superoxide dismutase (SOD) activity, which generates H2O2 via dismutase of superoxide ions. Total SOD activity in Xac-infected leaves increased to a maximum at 4 dai, the day of highest H2O2 concentration, and then declined and remained at or below controls. Mn-SOD and Fe-SOD activities both increased to maximum activities at 4 dai. Mn-SOD had four isoforms in Xac-infected leaves but only three in the controls. Fe-SOD had three isoforms in both infected and control plants. Suppression of H2O2 in Xac-infected leaves also corresponded to higher activities of the H2O2 catabolising enzymes catalase (CAT), ascorbate peroxidase (APOD), and peroxidase (POD). Two additional CAT isoforms were detected in infected leaves and not the controls. Three POD isoforms were detected in both control and infected leaves. Previous research has shown that Xac is sensitive to intraplant H2O2 concentration, however, the pattern of Xac in this study did not correspond to H2O2 concentration, which initially increased due to enhanced SOD activity, but was later suppressed apparently with the aid of peroxidases. In conclusion, Xac infection altered H2O2 metabolism in grapefruit leaves by changes in the activities and isoforms of SODs, CATs, PODs and APOD.  相似文献   

5.
This article describes the employment of a novel p-phenol derivative, 4-(1,2,4-triazol-1-yl)phenol (TRP), as a highly potent signal enhancer of the luminol-hydrogen peroxide (H2O2)-horseradish peroxidase (HRP) chemiluminescence (CL) system. The CL reaction conditions were optimized, and the enhancement characteristics of TRP were compared with those of p-iodophenol (PIP). TRP produced a strong enhancement of the CL with the effect of prolonging the light emission. The developed system was then applied to the determination of H2O2 with immobilized HRP using magnetic beads as a solid support. The linear range for H2O2 was 2.0 × 10−6 to 1.0 × 10−3 M. The detection limit for H2O2 was 2.0 × 10−6 M. The proposed sensor was applied successfully to the determination of H2O2 in rainwater.  相似文献   

6.
During infection, Mycobacterium leprae is faced with the host macrophagic environment limiting the growth of the bacilli. However, (pseudo-)enzymatic detoxification systems, including truncated hemoglobin O (Ml-trHbO), could allow this mycobacterium to persist in vivo. Here, kinetics of peroxynitrite (ONOOH/ONOO) detoxification by ferryl Ml-trHbO (Ml-trHbOFe(IV)O), obtained by treatment with H2O2, is reported. Values of the second-order rate constant for peroxynitrite detoxification by Ml-trHbOFe(IV)O (i.e., of Ml-trHbOFe(III) formation; kon), at pH 7.2 and 22.0 °C, are 1.5 × 104 M−1 s−1, and 2.2 × 104 M−1 s−1, in the absence of and presence of physiological levels of CO2 (∼1.2 × 10−3 M), respectively. Values of kon increase on decreasing pH with a pKa value of 6.7, this suggests that ONOOH reacts preferentially with Ml-trHbOFe(IV)O. In turn, peroxynitrite acts as an antioxidant of Ml-trHbOFe(IV)O, which could be responsible for the oxidative damage of the mycobacterium. As a whole, Ml-trHbO can undertake within the same cycle H2O2 and peroxynitrite detoxification.  相似文献   

7.
An enzyme preparation from suspension cultured tobacco cells oxidized IAA only in the presence of added cofactors, Mn2+ and 2,4-dichlorophenol, and showed two pH optima for the oxidation at pH 4·5 and 5·5. Effects of various phenolic compounds and metal ions on IAA oxidase activity were examined. The properties of seven peroxidase fractions separated by column chromatography on DEAE-cellulose and CM-Sephadex, were compared. The peroxidases were different in relative activity toward o-dianisidine and guaiacol. All the peroxidases catalysed IAA oxidation in the presence of added cofactors. The pH optima for guaiacol peroxidation were very similar among the seven isozymes, but the optima for IAA oxidation were different. The anionic and neutral fractions showed pH optima near pH 5·5, but the cationic isozymes showed optima near pH 4·5. With guaiacol as hydrogen donor, an anionic peroxidase (A-1) and a cationic peroxidase (C-4) were very different in H2O2 concentration requirements for their activity. Peroxidase A-1 was active at a wide range of H2O2 concentrations, while peroxidase C-4 showed a more restricted H2O2 requirement. Gel filtration and polyacrylamide gel studies indicated that the three cationic peroxidases have the same molecular weight.  相似文献   

8.
9.
Two extracellular humic acids peroxidases called HaP1 and HaP2 were isolated from the Streptomyces sp. strain AM2 and, based on MALDI-TOF MS analysis. The purified enzymes were determined as monomers with molecular masses of 40,351.11 and 25,175.19 Da, respectively. The N-terminal amino acid sequences of HaP1 and HaP2 were identified, and their optimum pH values were determined as 6 and 7.5, respectively. Standard 2,4-dichlorophenol (2,4-DCP) assays showed that both enzymes had maximal activity at 55 °C. HaP2 was stable at 55 °C for more than 24 h and had a half-life of 90 min at 65 °C. Although the catalytic properties of HaP1 and HaP2 were nearly identical, their stabilities and Reinheitzahl (RZ) values were substantially different. Both peroxidases were found to be heme proteins that catalyzed the oxidation of a wide range of substrates in the presence of hydrogen peroxide (H2O2), with HaP2 exhibiting a broader range of substrate specificity. The characterization of peroxidase activity revealed activity against humic acids, guiacol, 2,4-DCP, l-3,4-dihydroxyphenylalanine, and 2,4,5-trichlorophenol as well as other chlorophenols in the presence of H2O2. However, the inhibition of peroxidase activity by the addition of potassium cyanide and sodium azide also indicated the presence of heme components in the tertiary structure of these enzymes.  相似文献   

10.
Three kinds of copper(II) azide complexes have been synthesised in excellent yields by reacting Cu(ClO4)2 · 6H2O with N,N-bis(2-pyridylmethyl)amine (L1); N-(2-pyridylmethyl)-N′,N′-dimethylethylenediamine (L2); and N-(2-pyridylmethyl)-N′,N′-diethylethylenediamine (L3), respectively, in the presence of slight excess of sodium azide. They are the monomeric Cu(L1)(N3)(ClO4) (1), the end-to-end diazido-bridged Cu2(L2)2(μ-1,3-N3)2(ClO4)2 (2) and the single azido-bridged (μ-1,3-) 1D chain [Cu(L3)(μ-1,3-N3)]n(ClO4)n (3). The crystal and molecular structures of these complexes have been solved. The variable temperature magnetic moments of type 2 and type 3 complexes were studied. Temperature dependent susceptibility for 2 was fitted using the Bleaney-Bowers expression which led to the parameters J = −3.43 cm−1 and R = 1 × 10−5. The magnetic data for 3 were fitted to Baker’s expression for S = 1/2 and the parameters obtained were J = 1.6 cm−1 and R = 3.2 × 10−4. Crystal data are as follows. Cu(L1)(N3)(ClO4): Chemical formula, C12H13ClN6O4Cu; crystal system, monoclinic; space group, P21/c; a = 8.788(12), b = 13.045(15), c = 14.213(15) Å; β = 102.960(10)°; Z = 4. Cu(L2)(μ-N3)(ClO4): Chemical formula, C10H17ClN6O4Cu: crystal system, monoclinic; space group, P21/c; a = 10.790(12), b = 8.568(9), c = 16.651(17) Å; β = 102.360(10)°; Z = 4. [Cu(L3)(μ-N3)](ClO4): Chemical formula, C12H21ClN6O4Cu; crystal system, monoclinic; space group, P21/c; a = 12.331(14), b = 7.804(9), c = 18.64(2) Å; β = 103.405(10)°; Z = 4.  相似文献   

11.
In order to examine the effects of coordinated hydroxide ion and free hydroxide ion in configurational conversion of a tetraamine macrocyclic ligand complex, the kinetics of the cis-to-planar interconversion of cis-[Ni(isocyclam)(H2O)2]2+ (isocyclam, 1,4,7,11-tetraazacyclotetradecane) has been studied spectrophotometrically in basic aqueous solution. The interconversion requires the inversion of one sec-NH center of the folded cis-complex to have the planar species. Kinetic data are satisfactorily fitted by the rate law, R = kOH[OH][cis-[Ni(isocyclam)(H2O)2]2+], where kOH = 3.84 × 103 dm3 mol−1 s−1 at 25.0 ± 0.1 °C with I = 0.10 mol dm−3 (NaClO4). The large ΔH, 61.7 ± 3.2 kJ mol−1, and the large positive ΔS, 30.2 ± 10.8 J K−1 mol−1, strongly support a free-base-catalyzed mechanism for the reaction.  相似文献   

12.
Reaction of [Ru2(O2CMe)4]Cl with K3[Cr(CN)5NO] in water forms Hx[RuII/III2(O2CMe)4]3−x-[Cr(CN)5NO]·zH2O (x = 0.2) that magnetically orders at 4.0 K and possesses an interpenetrating body centered cubic [a = 13.2509(2) Å] structure with random locations of the bridging nitrosyl ligands, and x/3 vacant cation sites. Similarly, the aqueous reaction of [Ru2(O2CMe)4]Cl with Na2[Fe(CN)5NO] forms paramagnetic [Ru2(O2CMe)4]2[Fe(CN)5NO]·H2O, which has a similar tetragonal interpenetrating structure [a = 13.0186(1) Å, c = 13.0699(2) Å] where the NO ligands are presumably nonbridging and 1/3 of the expected cation sites are unoccupied. The presence of uncoordinated NO sites in addition to missing neighboring [Ru2(O2CMe)4]+ units, results in significant vacancies (or holes) in the lattice.  相似文献   

13.
Basal metabolic rate (BMR) is thought to be a major hub in the network of physiological mechanisms connecting life history traits. Evaporative water loss (EWL) is a physiological indicator that is widely used to measure water relations in inter- or intraspecific studies of birds in different environments. In this study, we examined the physiological responses of summer-acclimatized Hwamei Garrulax canorus to temperature by measuring their body temperature (Tb), metabolic rate (MR) and EWL at ambient temperatures (Ta) between 5 and 40 °C. Overall, we found that mean body temperature was 42.4 °C and average minimum thermal conductance (C) was 0.15 ml O2 g−1 h−1 °C−1 measured between 5 and 20 °C. The thermal neutral zone (TNZ) was 31.8–35.3 °C and BMR was 181.83 ml O2 h−1. Below the lower critical temperature, MR increased linearly with decreasing Ta according to the relationship: MR (ml O2 h−1)=266.59–2.66 Ta. At Tas above the upper critical temperature, MR increased with Ta according to the relationship: MR (ml O2 h−1)=−271.26+12.85 Ta. EWL increased with Ta according to the relationship: EWL (mg H2O h−1)=−19.16+12.64 Ta and exceeded metabolic water production at Ta>14.0 °C. The high Tb and thermal conductance, low BMR, narrow TNZ, and high evaporative water production/metabolic water production (EWP/MWP) ratio in the Hwamei are consistent with the idea that this species is adapted to warm, mesic climates, where metabolic thermogenesis and water conservation are not strong selective pressures.  相似文献   

14.
In our study, we showed that at a relatively low concentration, H2O2 can irreversibly inactivate the human brain type of creatine kinase (HBCK) and that HBCK is inactivated in an H2O2 concentration-dependent manner. HBCK is completely inactivated when incubated with 2 mM H2O2 for 1 h (pH 8.0, 25 °C). Inactivation of HBCK is a two-stage process with a fast stage (k1 = 0.050 ± 0.002 min−1) and a slow (k2 = 0.022 ± 0.003 min−1) stage. HBCK inactivation by H2O2 was affected by pH and therefore we determined the pH profile of HBCK inactivation by H2O2. H2O2-induced inactivation could not be recovered by reducing agents such as dl-dithiothreitol, N-acetyl-l-cysteine, and l-glutathione reduced. When HBCK was treated with DTNB, an enzyme substrate that reacts specifically with active site cysteines, the enzyme became resistant to H2O2. HBCK binding to Mg2+ATP and creatine can also prevent H2O2 inactivation. Intrinsic and 1-anilinonaphthalene-8-sulfonate-binding fluorescence data showed no tertiary structure changes after H2O2 treatment. The thiol group content of H2O2-treated HBCK was reduced by 13% (approximately 1 thiol group per HBCK dimer, theoretically). For further insight, we performed a simulation of HBCK and H2O2 docking that suggested the CYS283 residue could interact with H2O2. Considering these results and the asymmetrical structure of HBCK, we propose that H2O2 specifically targets the active site cysteine of HBCK to inactivate HBCK, but that substrate-bound HBCK is resistant to H2O2. Our findings suggest the existence of a previously unknown negative form of regulation of HBCK via reactive oxygen species.  相似文献   

15.
The assay conditions for the spectrophotometric quantification of horseradish peroxidase (HRP) with the chromogenic substrate o-phenylenediamine (OPD) at 25 °C in the presence of hydrogen peroxide (H2O2) were optimized. With [OPD]0 = 3.14 mM and [H2O2]0 = 80 μM at pH 7.2, the initial formation of only one of the possible reaction products and intermediates, 2,3-diaminophenazine (DAP, λmax = 417 nm), was observed. The rate of DAP formation during the first 30 min of reaction was followed spectrophotometrically and found to linearly depend on the HRP concentration between 5 and 45 pM under the conditions used.  相似文献   

16.
Joachim Reimann  Pia Ädelroth 《BBA》2007,1767(5):362-373
Nitric oxide reductase (NOR) from P. denitrificans is a membrane-bound protein complex that catalyses the reduction of NO to N2O (2NO + 2e + 2H+ → N2O + H2O) as part of the denitrification process. Even though NO reduction is a highly exergonic reaction, and NOR belongs to the superfamily of O2-reducing, proton-pumping heme-copper oxidases (HCuOs), previous measurements have indicated that the reaction catalyzed by NOR is non-electrogenic, i.e. not contributing to the proton electrochemical gradient. Since electrons are provided by donors in the periplasm, this non-electrogenicity implies that the substrate protons are also taken up from the periplasm. Here, using direct measurements in liposome-reconstituted NOR during reduction of both NO and the alternative substrate O2, we demonstrate that protons are indeed consumed from the ‘outside’. First, multiple turnover reduction of O2 resulted in an increase in pH on the outside of the NOR-vesicles. Second, comparison of electrical potential generation in NOR-liposomes during oxidation of the reduced enzyme by either NO or O2 shows that the proton transfer signals are very similar for the two substrates proving the usefulness of O2 as a model substrate for these studies. Last, optical measurements during single-turnover oxidation by O2 show electron transfer coupled to proton uptake from outside the NOR-liposomes with a τ = 15 ms, similar to results obtained for net proton uptake in solubilised NOR [U. Flock, N.J. Watmough, P. Ädelroth, Electron/proton coupling in bacterial nitric oxide reductase during reduction of oxygen, Biochemistry 44 (2005) 10711-10719]. NOR must thus contain a proton transfer pathway leading from the periplasmic surface into the active site. Using homology modeling with the structures of HCuOs as templates, we constructed a 3D model of the NorB catalytic subunit from P. denitrificans in order to search for such a pathway. A plausible pathway, consisting of conserved protonatable residues, is suggested.  相似文献   

17.
Reactive oxygen species play a dual role in host-pathogen interaction. They impede the spread of biotrophic pathogens via stimulating cell death and hypersensitive response (HR), and, on the other hand, they provide access to nutrients for necrotrophic pathogens feeding on dead tissues and facilitate their colonizing the host. The participation of ROS in defending plants from pathogens with a combined lifestyle (hemibiotrophs) is not yet understood, and it varies in its dependence on the particular host-pathogen combination. In the present study, we inoculated rapeseed plants (Brassica napus) with a hemibiotrophic fungus, Leptosphaeria maculans, and manipulated the H2O2 content in cotyledons by infiltrating catalase and/or H2O2 into tissues. The action of catalase resulted in a significant decrease in lesions development, but when H2O2 was applied instead, lesion formation was only moderately stimulated compared to the untreated control. When H2O2 toxicity to L. maculans was tested in vitro, concentrations above 5 mM and 10 mM H2O2 were lethal for germinating conidia and growing mycelia of L. maculans, respectively. We can assume that L. maculans behaves as a necrotroph during this early stage of infection even though its resistance to H2O2 does not exceed standard concentrations. To investigate antioxidant mechanisms implicated in the response of B. napus to L. maculans, the cotyledons were both inoculated with conidia and treated with L. maculans elicitor. Increased activities of guaiacol peroxidase, ascorbate peroxidase, glutathione reductase and superoxide dismutase were recorded both in L. maculans-infected and elicitor-treated cotyledons. The results indicate the importance of these enzymes for ROS scavenging in B. napus-L. maculans interaction.  相似文献   

18.
The in-situ formed hydrazone Schiff base ligand (E)-N′-(2-oxy-3-methoxybenzylidene)benzohydrazide (L2−) reacts with copper(II) acetate to a tetranuclear open cubane [Cu(L)]4 complex which crystallizes as two symmetry-independent (Z′ = 2) S4-symmetrical molecules in different twofold special positions with a homodromic water tetramer. The two independent (A and B) open- or pseudo-cubanes with Cu4O4 cores of 4 + 2 class (Ruiz classification) each have three different magnetic exchange pathways leading to an overall antiferromagnetic coupling with J1B = J2B = −17.2 cm−1, J1A = −36.7 cm−1, J2A = −159 cm−1, J3A = J3B = 33.5 cm−1, g = 2.40 and ρ = 0.0687. The magnetic properties have been analysed using the H = −Σi,jJij(SiSj) spin Hamiltonian.  相似文献   

19.
Outdoor pot experiments were conducted in California to quantify differences in rice and Schoenoplectus mucronatus susceptibility to drought and to identify morphological and physiological traits that would favor rice over S. mucronatus under drought. Plants were grown in flooded soil for approximately 5 weeks, and then subjected to different drought periods after which pots were re-flooded. Chlorophyll fluorescence assays revealed that rice and S. mucronatus Fv/Fm first became <0.8 after leaf water potential (Ψleaf) had decreased to approximately −4 MPa and −2 MPa, respectively. Thus, by suffering less photosynthetic damage from drought, rice had better recovery after re-flooding than S. mucronatus. When drought reduced Ψleaf to −3 MPa, S. mucronatus re-growth was nearly suppressed but that of rice was unaffected. Rice plants depleted soil moisture 1.6 faster than S. mucronatus due to larger and deeper roots and a high water-spending strategy (when Ψleaf decreased from approximately −0.5 MPa to −2.5 MPa, 13δ increased from −27.8 to −27.4 and from −28.1 to −26.0 for rice and S. mucronatus, respectively). Rice under interspecific competition sustained its Ψleaf by extracting more water from greater depths, while causing severe moisture stress and photosynthetic damage to S. mucronatus. Thus temporary drought enhanced rice competitiveness over S. mucronatus, supporting the concept of using brief drought as a tool for S. mucronatus suppression in rice. The Ψleaf developed by the end of the drought period predicted rice yields (R2 = 0.77, P < 0.0001) and the capacity of S. mucronatus to recover from drought upon irrigation resumption (R2 = 0.62, P < 0.001). Brief (8-10 d) drought imposed on 5-week-old rice did not significantly depress late-season rice biomass growth or grain yields, while S. mucronatus never fully recovered from drought. Rice yields were only reduced after Ψleaf reached values below approximately −2.5 MPa. Longer drought (∼20 d) delayed maturity and reduced rice yields by approximately 60-80%. The dry-down approach could help suppress weeds similar to S. mucronatus in organic rice where premium prices can compensate for lower grain yield.  相似文献   

20.
This experimental study quantified and compared particle-mixing and solute transport by the polychaetes Marenzelleria neglecta (2 g ww, 3200 ind. m− 2) and Hediste diversicolor (2 g ww, 800 ind. m− 2) in Baltic Sea sediments. Particle tracers (luminophores) were added to the sediment surface and their vertical distribution in the sediment was measured after 10 d. The rate of particle mixing was quantified using a gallery-diffusion model calculating the biodiffusion coefficient Db and the non-local transport parameter r. Bioirrigation was measured by adding an inert solute tracer (bromide) to the overlying water 1, 1.5 and 2 d before the end of the experiment, and quantified by calculating the net bromide flux and fitting the bromide profiles to a 1D diffusion model providing an apparent biodiffusion coefficient Da. The two polychaete worms displayed similar particle-mixing and solute transport efficiencies (based on total biomass) despite different modes of bioturbation. However, H. diversicolor was a more efficient particle-reworker and M. neglecta a more efficient bioirrigator, on an individual level. H. diversicolor buried a higher percentage (13%) of luminophores below the top 0.5 cm surface layer than M. neglecta (6%). Db did not differ between the two species (2.4 × 10− 3 cm2 d− 1) indicating a similar rate of diffusive mixing of the top sediment, however, the non-local transport parameter r was 2.5 y− 1 for H. diversicolor and zero for M. neglecta, suggesting no significant particle-transport below the biodiffusive layer by M. neglecta. The average individual net bromide fluxes obtained were ca. 0.01 mL min− 1 for H. diversicolor and 0.003 mL min− 1 for M. neglecta, corresponding to an area-specific rate of ca. 12 L m− 2 d− 1 at the used densities. Da did not differ between the two polychaetes, suggesting a higher individual solute exchange efficiency of M. neglecta considering the much higher ventilation rates reported for H. diversicolor than for Marenzelleria sp. The ongoing colonization of Baltic Sea sediments by M. neglecta at high densities may thus lead to an enhanced soluble release of both nutrients and contaminants. These results add information to the understanding of the potential effects of the invasion of M. neglecta on sediment biogeochemistry when competing with and/or replacing native species.  相似文献   

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