共查询到20条相似文献,搜索用时 21 毫秒
1.
Two chromium-resistant bacterial strains, Bacillus cereus S-6 and Ochrobactrum intermedium CrT-1, and two cyanobacterial strains, Oscillatoria sp. and Synechocystis sp., were used in this study. At initial chromate concentrations of 300 and 600 μg K2CrO4 mL−1, and an inoculum size of 9.6×107 cells mL−1, B. cereus S-6 completely reduced Cr(VI), while O. intermedium CrT-1 reduced Cr(VI) by 98% and 70%, respectively after 96 h. At 100 μg K2CrO4 mL−1, Synechocystis sp. MK(S) and Oscillatoria sp. BJ2 reduced 62.1% and 39.9% of Cr(VI), respectively, at 30°C and pH 8. Application of hexavalent chromate salts adversely affected wheat seedling growth and anatomical characters. However, bacterial inoculation alleviated the toxic effects, as reflected by significant improvements in growth as well as anatomical parameters. Cyanobacterial strains also led to some enhancement of various growth parameters in wheat seedlings. 相似文献
2.
Two chromium-resistant bacterial strains, CrT-1 and CrT-13, tolerant up to 40mg K 2CrO 4 ml –1 on nutrient agar, 25mgml –1 in nutrient broth, and up to 10mgml –1 in acetate-minimal media, were identified as Ochrobactrum intermedium and Brevibacterium sp., respectively, on the basis of 16S rRNA gene sequencing. Uptake of chromate was greater in living cells than in heat-killed on dried cells. CrT-1 reduced 82%, 28% and 16% of Cr(VI) at 100, 500, and 1000gml –1 after 24h while CrT-13 reduced 41%, 14% and 9%. Other heavy metals at low concentrations did not affect these reductions. At 150 and 300gml –1 in an industrial effluent sample Cr(VI) was reduced by 87% and 71%, respectively, with CrT-1 and by 68% and 47% with CrT-13.Revisions requested 17 May 2004; Revisions received 2 July 2004 相似文献
3.
Chromium (Cr) is a heavy metal risk to human health, and a contaminant found in agricultural soils and industrial sites. Phytoremediation, which relies on phytoextraction of Cr with biological organisms, is an important alternative to costly physical and chemical methods of treating contaminated sites. The ability of the arbuscular mycorrhizal fungus (AM), Glomus intraradices, to enhance Cr uptake and plant tolerance was tested on the growth and gas exchange of sunflower ( Helianthus annuus L.). Mycorrhizal-colonized (AM) and non-inoculated (Non-AM) sunflower plants were subjected to two Cr species [trivalent cation (Cr 3+) Cr(III) , and divalent dichromate anion (Cr 2O 7−) Cr(VI) ]. Both Cr species depressed plant growth, decreased net photosynthesis ( A) and increased the vapor pressure difference; however, Cr(VI) was more toxic. Chromium accumulation was greatest in roots, intermediate in stems and leaves, and lowest in flowers. Greater Cr accumulation occurred with Cr(VI) than Cr(III). AM enhanced the ability of sunflower plants to tolerate and hyperaccumulate Cr. At higher Cr levels greater mycorrhizal dependency occurred, as indicated by proportionally greater growth, higher A and reduced visual symptoms of stress, compared to Non-AM plants. AM plants had greater Cr-accumulating ability than Non-AM plants at the highest concentrations of Cr(III) and Cr(VI), as indicated by the greater Cr phytoextraction coefficient. Mycorrhizal colonization (arbuscule, vesicle, and hyphae formation) was more adversely affected by Cr(VI) than Cr(III), however high levels of colonization still occurred at even the most toxic levels. Arbuscules, which play an important role in mineral ion exchange in root cortical cells, had the greatest sensitivity to Cr toxicity. Higher levels of both Cr species reduced leaf tissue phosphorus (P). While tissue P was higher in AM plants at the highest Cr(III) level, tissue P did not account for mycorrhizal benefits observed with Cr(VI) plants. 相似文献
4.
Impact of four chromium resistant bacterial strains (S3, S4, S6, and S7) was studied on the different growth parameters of
sunflower ( Helianthus annuus var SF-187) in chromium free or under chromium stress. Strains used exhibited very high-level resistance to chromate (up
to 50 mg ml -1 on nutrient agar and 1-2 mg ml -1 in minimal medium). Application of Cr(VI) salt adversely affected the seed germination, root and shoot length, and fresh
weight of seedlings. Bacterial inoculations improved the growth parameters. The effects of Cr(VI) on the different biochemical
parameters were also very severe but seedlings inoculated with bacteria showed much improvements as compared to non-inoculated
controls. Uptake of Cr(VI) was higher than Cr(III) by the seedlings. Inoculated seedlings contained less chromium than non-inoculated
seedlings. Much improvement in the internal region of root and shoot was observed in inoculated plants especially in guard
cells. 相似文献
5.
We isolated four cultures of chromate resistant, unicellular, non-motile green algae from disposal sites of the paper-pulp
and electroplating industries. These algae were maintained in Tris-acetate-glycerophosphate medium containing 30 μM K 2Cr 2O 7. The morphological features as well as analysis of the 500-bp fragment of 18S rDNA (NS 12 region) showed that these isolates
belong to Chlorella spp. These isolates showed EC 50 values for chromate ranging from 60 to 125 μM. Uptake studies with radioactive 51Cr(VI) showed that 10–19% of total radioactivity was intracellular, and 1–2% was bound to the cell wall. The rest of the activity
remained in the medium, suggesting that resistance was not related to accumulation of Cr(VI) in the cells. Interestingly,
when these isolates were grown in the presence of 30 μM of K 2Cr 2O 7, a decrease in the Cr(VI) concentration in the medium was observed. Only live cells could deplete Cr(VI) from the supernatant,
suggesting the presence of chromium reduction activity in these Chlorella isolates. Cr(VI) reduction activity of the cells of Chlorella was stimulated by light as well as by acetate and glycerophosphate. Treatment of Chlorella cells with 3-(3,4 dichlorophenyl),1,1dimethyl urea (DCMU) did not affect the Cr(VI) reduction. However, if the cells were
treated with sodium azide, Cr(VI) reduction was severely affected. Though chromate resistance has been well documented in
algae, the information on chromate reduction by algae is scant. This paper discusses the Cr(VI) reduction by Cr(VI) resistant
Chlorella, which may find a use in the effective bioremediation of Cr(VI). 相似文献
6.
Two chromium-resistant bacterial strains, Bacillus cereus S-6 and Ochrobactrum intermedium CrT-1, and two cyanobacterial strains, Oscillatoria sp. and Synechocystis sp., were used in this study. At initial chromate concentrations of 300 and 600 microg K2CrO4 mL(-1), and an inoculum size of 9.6 x 10(7) cells mL(-1), B. cereus S-6 completely reduced Cr(VI), while O. intermedium CrT-1 reduced Cr(VI) by 98% and 70%, respectively after 96 h. At 100 microg K2CrO4 mL(-1), Synechocystis sp. MK(S) and Oscillatoria sp. BJ2 reduced 62.1% and 39.9% of Cr(VI), respectively, at 30 degrees C and pH 8. Application of hexavalent chromate salts adversely affected wheat seedling growth and anatomical characters. However, bacterial inoculation alleviated the toxic effects, as reflected by significant improvements in growth as well as anatomical parameters. Cyanobacterial strains also led to some enhancement of various growth parameters in wheat seedlings. 相似文献
7.
Summary The activity of antioxidative enzymes after inoculation of pepper ( Capsicum annuum L. Chungok) with a pathogen, Phytophthora capsici (P), the causal agent of Phytophtora blight and dual inoculation of pathogen and an antagonist, Paenibacillus illinoisensis KJA-424 (P+A), were measured and compared with that of non-inoculated (C) roots. Root mortality was significantly reduced by about 84% in P+A treatment compared with P treatment alone. When compared to the non-inoculated (C) roots, malondialdehyde (MDA) concentration gradually decreased by 52.4% in 7 days only in P-treated roots and hydrogen peroxide (H 2O 2) was not significantly affected by the treatment for 5 days but significantly decreased in the P+A-treated roots at day 7. P-treatment continuously induced peroxidase (POD) and superoxide dismutase (SOD), resulting in significant increases of 36.7% and 27.7% at day 7, respectively, compared to the control. In P+A-treated roots, the activities of POD and SOD also increased for 5 days but returned to the control level at day 7. Catalase activity fluctuated but again increased over the 7-day period following P+A inoculation. These results indicate that an antagonist P. illinoisensis KJA-424 alleviated root mortality and suppressed the elevated activities of POD and SOD in the root of pepper plant root caused by P.␣capsici infection. 相似文献
8.
AIMS: This study assessed the plant growth-promoting ability of the bacterial strains Ochrobactrum intermedium (isolate CrT-1) and Bacillus cereus (isolate S-6). METHODS AND RESULTS: Two chromium resistant bacterial strains isolated from chromium-contaminated wastewater and soils were identified as O. intermedium CrT-1 and B. cereus S-6. These strains were inoculated on seeds of mungbean Vigna radiata var NM-92, which were germinated and grown under chromate salts (300 microg ml(-1) of CrCl(3)or K(2)CrO(4)). The data show that Cr(VI) was more toxic because of its better availability to plants roots when compared with Cr(III). The major part of Cr(VI) supplied to the seedlings was reduced to Cr(III) in the rhizosphere by the bacterial strains, thus lowering the toxicity of chromium to seedlings. CONCLUSIONS: Strains have significant Cr(VI) resistance and reduction potential and have ability to enhance mungbean plant growth under chromium stress. SIGNIFICANCE AND IMPACT OF THE STUDY: These strains could be utilized for the growth of economically important cash crops as well as for the bioremediation of chromium-polluted soils. 相似文献
9.
[背景] 异化铁还原细菌能够在还原Fe (III)的同时将毒性较大的Cr (VI)还原成毒性较小的Cr (III),解决铬污染的问题。 [目的] 基于丁酸梭菌( Clostridium butyricum) LQ25异化铁还原过程制备生物磁铁矿,开展异化铁还原细菌还原Cr (VI)的特性研究。 [方法] 构建以氢氧化铁为电子受体和葡萄糖为电子供体的异化铁培养体系。菌株LQ25培养结束时制备生物磁铁矿。设置不同初始Cr (VI)浓度(5、10、15、25和30 mg/L),分别测定菌株LQ25对Cr (VI)还原效率以及生物磁铁矿对Cr (VI)的还原效率。 [结果] 菌株LQ25在设置的Cr (VI)浓度范围内都能良好生长。当Cr (VI)浓度为15 mg/L时,在异化铁培养条件下,菌株LQ25对Cr (VI)的还原率为63.45%±5.13%,生物磁铁矿对Cr (VI)的还原率为87.73%±9.12%,相比菌株还原Cr (VI)的效率提高38%。pH变化能影响生物磁铁矿对Cr (VI)的还原率,当pH 2.0时,生物磁铁矿对Cr (VI)的还原率最高,几乎达到100%。电子显微镜观察发现生物磁铁矿表面有许多孔隙,X-射线衍射图谱显示生物磁铁矿中Fe (II)的存在形式是Fe (OH) 2。 [结论] 基于异化铁还原细菌制备生物磁铁矿可用于还原Cr (VI),这是一种有效去除Cr (VI)的途径。 相似文献
10.
Oxidative stress due to hexavalent chromium [Cr(VI)] in Vigna radiata seedlings, and stress amelioration with treatment of methanol extract of Rhododendron arboreum leaves was observed in the present study by analyzing growth parameters, stomatal morphology, malondialdehyde (MDA) content, histological analysis, pigment contents, Cr metal uptake, elemental analysis, and antioxidant analysis. Chromium treatment resulted in the decline of root length, shoot length, fresh weight, and dry weight. Scanning electron microscopic studies revealed that Cr treatment altered the stomatal structure. As compared to control plants, MDA content increased by 80.1% in Cr-treated plants. Histological analysis with confocal microscope confirmed the nuclear damage, membrane damage, enhanced H2O2 accumulation, and decline in pigment concentration. Atomic absorption spectrometry analysis revealed an accumulation of 43.3% Chromium in the plant tissues and decreased concentration of essential elements as consequences of Cr treatment. The methanol extract of R. arboreum leaves (MEL) alleviated Cr stress in Vigna radiata seedlings by restoring normal growth, stomatal structure, and pigment contents, as well as essential elements. Reduction in H2O2 accumulation, reduced MDA content by 29.2%, and decline in Cr accumulation to 32.8% was observed after MEL supplementation to Cr-stressed plants. Decreased nuclear and membrane damage along with increased lipid-soluble as well as water-soluble antioxidants after MEL application in Cr-stressed plants are further symptoms of stress amelioration properties of Rhododendron leaves. 相似文献
11.
Desulfovibrio vulgaris Hildenborough is a well-studied sulfate reducer that can reduce heavy metals and radionuclides [e.g., Cr(VI) and U(VI)].
Cultures grown in a defined medium had a lag period of approximately 30 h when exposed to 0.05 mM Cr(VI). Substrate analyses
revealed that although Cr(VI) was reduced within the first 5 h, growth was not observed for an additional 20 h. The growth
lag could be explained by a decline in cell viability; however, during this time small amounts of lactate were still utilized
without sulfate reduction or acetate formation. Approximately 40 h after Cr exposure (0.05 mM), sulfate reduction occurred
concurrently with the accumulation of acetate. Similar amounts of hydrogen were produced by Cr-exposed cells compared to control
cells, and lactate was not converted to glycogen during non-growth conditions. D. vulgaris cells treated with a reducing agent and then exposed to Cr(VI) still experienced a growth lag, but the addition of ascorbate
at the time of Cr(VI) addition prevented the lag period. In addition, cells grown on pyruvate displayed more tolerance to
Cr(VI) compared to lactate-grown cells. These results indicated that D. vulgaris utilized lactate during Cr(VI) exposure without the reduction of sulfate or production of acetate, and that ascorbate and
pyruvate could protect D. vulgaris cells from Cr(VI)/Cr(III) toxicity.
J.D. Wall and M.W. Fields are both affiliated to the Virtual Institute of Microbial Stress and Survival ().
M.E. Clark and S.B. Thieman contributed equally to this work. 相似文献
12.
Two chromium-resistant bacterial strains, CrT-1 and CrT-13, tolerant up to 40 mg K2CrO4 ml(-1) on nutrient agar, 25 mg ml(-1) in nutrient broth, and up to 10 mg ml(-1) in acetate-minimal media, were identified as Ochrobactrum intermedium and Brevibacterium sp., respectively, on the basis of 16S rRNA gene sequencing. Uptake of chromate was greater in living cells than in heat-killed on dried cells. CrT-1 reduced 82%, 28% and 16% of Cr(VI) at 100, 500, and 1000 microg ml(-1) after 24 h while CrT-13 reduced 41%, 14% and 9%. Other heavy metals at low concentrations did not affect these reductions. At 150 and 300 microg ml(-1) in an industrial effluent sample Cr(VI) was reduced by 87% and 71%, respectively, with CrT-1 and by 68% and 47% with CrT-13. 相似文献
13.
Chromium(VI) removal and its association with exopolysaccharide (EPS) production in cyanobacteria were investigated. Synechocystis sp. BASO670 produced higher EPS (548 mg L −1) than Synechocystis sp. BASO672 (356 mg L −1). While the EC 50 of the Cr(VI) for Synechocystis sp. BASO670 and Synechocystis sp. BASO672 were determined as 11.5 mg L −1, and 2.0 mg L −1, respectively, there was no relation between Cr(VI) removal and EPS production. Synechocystis sp. BASO672, which has higher EPS value, removed (33%) more Cr(VI) than Synechocystis sp. BASO670. Monomer compositions of EPS of each of the isolates were determined differently. Synechocystis sp. BASO672 which removed higher Cr(VI), had higher values of uronic acid and glucuronic acid (192 μg/mg and 89%, respectively). Our results showed that EPS might play a role in Cr(VI) tolerance. Monomer composition, especially uronic acid and glucuronic acid content of EPS may have enhanced Cr(VI) removal. 相似文献
14.
Kinetic analysis of the reduction of Cr(VI) by resting cell suspensions of Desulfovibrio vulgaris ATCC 29579 and a new isolate, Desulfovibrio sp. (`Oz7') was studied using lactate as the electron donor at 30 °C. The apparent K
m ( K
m app) and V
max with respect to Cr(VI) reduction was compared for both strains. Desulfovibio sp. `Oz7' had a K
m app of 90 M (threefold lower than that of D. vulgaris ATCC 29579) and a V
max of 120 nmol h –1 mg –1 biomass dry wt (approx. 30% lower than for the reference strain). The potential of the new isolate for bioremediation of Cr(VI) wastewaters is discussed. 相似文献
15.
A Bacillus sp. RE was resistant to chromium and reduced Cr(VI) without accumulating chromium inside the cell. When Cr(VI) was 10 and
40 μg ml −1, >95% of the total Cr(VI) was reduced in 24 and 72 h of growth, respectively, whereas at 80 μg Cr(VI) ml −1 only 50% of Cr(VI) was reduced. However growth was not affected; the cell mass was 0.7–0.8 mg ml −1 in all cases. The cell-free extract showed Cr(VI) reducing enzyme activity which was enhanced (>5 fold) by NADH and NADPH.
Like whole cells the enzyme also reduced Cr(VI) with decreasing efficiency on increasing Cr(VI) concentration. The enzyme
activity was optimal at pH 6.0 and 30 °C. The enzyme was stable up to 30 °C and from pH 5.5 to 8, but from pH 4 to 5 the enzyme
was severely destabilized. Its Km and Vmax were 14 μm and 3.8 nmol min −1 mg −1 respectively. The enzyme activity was enhanced by Cu 2+ and Ni 2+ and inhibited by Hg 2+.
Received 21 September 2005; Revisions requested 5 October 2005; Revisions received 16 November 2005; Accepted 16 November
2005 相似文献
16.
The effect of ectomycorrhizal Pisolithus tinctorius ( Pt) infection was studied on the growth and photosynthetic characteristics of Pinus densiflora seedlings grown at ambient (360 µmol mol −1, AC) and elevated (720 µmol mol −1, EC) CO 2 concentrations. After 18 weeks, Pt inoculation had led to significantly increased dry mass and stem diameter of P. densiflora at both CO 2 concentrations, relative to non-inoculated seedlings. Moreover, EC significantly increased the ectomycorrhizal development. The phosphate content in needles inoculated with Pt was about three times higher than without inoculation at both CO 2 concentrations. The PAR saturated net photosynthetic rates ( P
sat) of P. densiflora inoculated with Pt were clearly higher than for control seedlings at both CO 2 concentrations, and the maximum net photosynthetic rate ( P
N) at saturated CO 2 concentration ( P
max) was higher than in controls. Moreover, the carboxylation efficiency (CE) and RuBP regeneration rate of the P
N/ C
i curve for P. densiflora inoculated with Pt were significantly higher than for non-inoculated seedlings at both CO 2 concentrations, especially at EC. The water use efficiency (WUE) of seedlings inoculated with Pt grown at EC was significantly raised. Allocation of photosynthates to roots was greater in Pt inoculated pine seedlings, because of the enhanced activity of ectomycorrhiza associated with seedlings at EC. Moreover, P
N of non-inoculated seedlings grown for 18 weeks at EC tended to be down regulated; in contrast, Pt inoculated seedlings showed no down-regulation at EC. The activity of ectomycorrhiza may therefore be enhanced physiological function related to water and phosphate absorption in P. densiflora seedlings at EC.This study was partly sponsored by the Ministry of Education, Sport, Culture, Science and Technology of Japan (RR2002, Basic Research B and Sprout study). 相似文献
17.
Overthelastfewdecadesenvironmentalcontaminationwithheavymetalshasincreaseddrastically .Heavymetalsfoundinwastewatersareharmfultotheenvironmentandtheireffectsonbiolo gicalsystemareverysevere.Anefficientandcheaptreatmentfortheirremovalandreuseofspentmetalsfromwastewaterneedstobedeve loped .Theremovaloftoxicmetalsfromtheenvironmentbymi croorganismshaspotentialasaneffectivemeansofremediatingheavymetalswastes.Microbe basedtechnologiescanprovideanalternativetoconventionalmethodsformetalremoval[1 ] .… 相似文献
18.
The main aim of this study was to investigate the influence of the sulfate ion on the tolerance to Cr(VI) and the Cr(VI) reduction
in a yeast strain isolated from tannery wastewater and identified as Candida sp. FGSFEP by the D1/D2 domain sequence of the 26S rRNA gene. The Candida sp. FGSFEP strain was grown in culture media with sulfate concentrations ranging from 0 to 23.92 mM, in absence and presence
of Cr(VI) [1.7 and 3.3 mM]. In absence of Cr(VI), the yeast specific growth rate was practically the same in every sulfate
concentration tested, which suggests that sulfate had no stimulating or inhibiting effect on the yeast cell growth. In contrast,
at the two initial Cr(VI) concentrations assayed, the specific growth rate of Candida sp. FGSFEP rose when sulfate concentration increased. Likewise, the greater efficiencies and volumetric rates of Cr(VI) reduction
exhibited by Candida sp. FGSFEP were obtained at high sulfate concentrations. Yeast was capable of reducing 100% of 1.7 mM Cr(VI) and 84% of 3.3 mM
Cr(VI), with rates of 0.98 and 0.44 mg Cr(VI)/L h, with 10 and 23.92 mM sulfate concentrations, respectively. These results
indicate that sulfate plays an important role in the tolerance to Cr(VI) and Cr(VI) reduction in Candida sp. FGSFEP. These findings may have significant implications in the biological treatment of Cr(VI)-laden wastewaters. 相似文献
19.
Chromium (III) accumulation in high biomass agricultural crops, sunflower (Helianthus annum) and Indian mustard (Brassica juncea) was studied using four soils (pH 4.6 to 7.6) contaminated with different rates of CrCl 3.6H 2O in the presence of synthetic chelate and organic acids. Chromium is essential for normal glucose metabolism in humans and animals, but its contamination and recovery from soils is of environmental concern. Adding ethylenediaminetetraacetic acid (EDTA), citric acid, or oxalic acid to Cr(III)‐contaminated soils significantly increased Cr concentration in plant shoots and roots. Adding Cr(III) complexes of EDTA, citric acid, and oxalic acid to soils dramatically increased (>200‐fold) Cr concentration in shoots and roots. Plant growth was severely decreased but was dependent on soil type, chelate rate, form, and time of chelate application. Chelates and organic acids enhanced Cr(III) accumulation, but its toxic effects were not avoided. Chromium(III) complexes were as toxic to plants as Cr(VI). The phytoaccumulation and recovery of Cr(III) from soils were limited and depended on soil type. 相似文献
20.
Growth, lipid peroxidation, H 2O 2 produciton and the response of the antioxidant enzymes and metabolites of the ascorbate glutathione pathway to oxidative stress caused by two concentrations (50 and 100 µM) of Cr(III) and Cr(VI) was studied in 15 day old seedlings of sorghum ( Sorghum bicolor (L.) Moench cv CO 27) after 10 days of treatment. Cr accumulation in sorghum plants was concentration and organ dependant. There was no significant growth retardation of plants under 50 µM Cr(III) stress. 100 µM Cr(VI) was most toxic of all the treatments in terms of root and leaf growth and oxidative stress. 50 µM Cr(VI) treated roots exhibited high significant increase in superoxide dismutase (SOD), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) (p < 0.01) and significant increases in catalse (CAT), ascorbate peroxidase (APX) and monodehydroascorbate reductase (MDHAR) (p < 0.05). A high increase in ascorbic acid (AA) level was seen in roots of 50 µM Cr(VI) treated plants in comparison with control. Levels of reduced glutathione (GSH) showed a varied and complex response in all the treatments in both plant parts. GSH/GSSG ratio was not affected by Cr(III) treatment in leaves, in contrast, roots exhibited significant reduction in the ratio. Results indicate that GSH depletion increased sensitivity to oxidative stress (Cr(VI) roots and leaves and Cr(III) 100 µM roots) and AA in tandem with APX compensated for GSH depletion by acting directly on H 2O 2 and the mechanism of defensive response in roots as well as leaves varied in its degree and effectiveness due to the concentration dependant differences observed in translocation of the element itself, reactive oxygen species ( ROS) generation and enzyme inhibition based on the oxidation state supplied to the plants. 相似文献
|