| 1. |
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| 2. |
- Desale, Prithviraj, et al.
(författare)
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Biosorption of nickel by Lysinibacillus sp. BA2 native to bauxite mine
- 2014
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Ingår i: Ecotoxicology and Environmental Safety. - : Elsevier. - 0147-6513 .- 1090-2414. ; 107, s. 260-268
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Tidskriftsartikel (refereegranskat)abstract
- The current scenario of environmental pollution urges the need for an effective solution for toxic heavy metal removal from industrial wastewater. Bioremediation is the most cost effective process employed by the use of microbes especially bacteria resistant to toxic metals. In this study, Lysinibacillus sp. BA2, a nickel tolerant strain isolated from bauxite mine was used for the biosorption of Ni(II). Lysinibacillus sp. BA2 biomass had isoelectric point (pI) of 3.3. The maximum negative zeta potential value (−39.45) was obtained at pH 6.0 which was highly favourable for Ni(II) biosorption. 238.04 mg of Ni(II) adsorbed on one gram of dead biomass and 196.32 mg adsorbed on one gram of live biomass. The adsorption of Ni(II) on biomass increased with time and attained saturation after 180 min with rapid biosorption in initial 30 min. The Langmuir and Freundlich isotherms could fit well for biosorption of Ni(II) by dead biomass while Langmuir isotherm provided a better fit for live biomass based on correlation coefficient values. The kinetic studies of Ni(II) removal, using dead and live biomass was well explained by second-order kinetic model. Ni(II) adsorption on live biomass was confirmed by SEM-EDX where cell aggregation and increasing irregularity of cell morphology was observed even though cells were in non-growing state. The FTIR analysis of biomass revealed the presence of carboxyl, hydroxyl and amino groups, which seem responsible for biosorption of Ni(II). The beads made using dead biomass of Lysinibacillus sp. BA2 could efficiently remove Ni(II) from effluent solutions. These microbial cells can substitute expensive methods for treating nickel contaminated industrial wastewaters.
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| 3. |
- Lundh, Dan, et al.
(författare)
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Arsenic accumulation in plants - Outlining strategies for developing improved variety of crops for avoiding arsenic toxicity in foods
- 2010
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Ingår i: Journal of biological systems. - : World Scientific Publishing. - 0218-3390. ; 18:1, s. 223-241
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Tidskriftsartikel (refereegranskat)abstract
- Contamination of food with arsenics is a potential health risk for both humans and animals in many regions of the world, especially in Asia. Arsenics can be accumulated in humans, animals and plants for a longer period and a long-term exposure of humans to arsenics results in severe damage of kidney, lever, heart etc. and many other vascular diseases. Arsenic contamination in human may also lead to development of cancer. In this paper we report our results on data mining approach (an in silico analysis based on searching of the existing genomic databases) for identification and characterization of genes that might be responsible for uptake, accumulation or metabolism of arsenics. For these in silico analyses we have involved the model plant Arabidopsis thaliana in our investigation. By employing a system biology model (a kinetic model) we have studied the molecular mechanisms of these processes in this plant. This model contains equations for uptake, metabolism and sequestration of different types of arsenic; As(V), As(III), MMAA and DMAA. The model was then implemented in the software XPP. The model was also validated against the data existing in the literatures. Based on the results of these in silico studies we have developed some strategies that can be used for reducing arsenic contents in different parts of the plant. Data mining experiments resulted in identification of two candidate genes (ACR2, arsenate reductase 2 and PCS1, phytochelatin synthase 1) that are involved either in uptake, transport or cellular localization of arsenic in A. thaliana. However, our system biology model revealed that by increasing the level of arsenate reductase together with an increased rate of arsenite sequestration in the vacuoles (by involving an arsenite efflux pump MRP1/2), it is possible to reduce the amount of arsenics in the shoots of A. thaliana to 11–12%.
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| 4. |
- Mandal, Abul, et al.
(författare)
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Modeling Arsenic Accumulation in Plants
- 2011
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Ingår i: Proceedings Second International Conference on Emerging Applications of Information Technology. - : IEEE Computer Society. - 9781424496839 - 9780769543291 ; , s. 133-137
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Konferensbidrag (refereegranskat)abstract
- Rice growing regions plagued by arsenic-contaminated soils and irrigation water do not have a viable option for producing arsenic-free crops. For instance, in Bangladesh every year more than 30 million people are affected from rice-derived arsenic contamination that contributes to arsenic levels known to cause health-related illnesses. Our strategy is to genetically-modify molecular mechanisms involved in the localization of arsenic to divert it to the non-edible parts of the plant. To identify viable candidate genes, we employed data mining, an in silico analysis based on searching existing genomic databases and in the genetic model plant Arabidopsis thaliana. To assist our investigation, we constructed a kinetic model to outline strategies for developing genetically-modified plants exhibiting a significant reduction in arsenic concentration in the edible parts (straw and grain). This model contains equations for uptake, metabolism and sequestration of different types of arsenic (As (V), As (III), MMAA and DMAA). The model was implemented using XPP and validated against existing data from the literature. From these analysis, we identified four candidate genes that are involved either in uptake, transport or cellular localization of arsenic in plants. But we found only one gene implicated in arsenic metabolism in rice. In parallel, we identified available T-DNA insertion mutants to determine the effects of these genes on arsenic accumulation. Results obtained from in silico data-mining, kinetic modeling, and assays with T-DNA insertion mutants will be used to design gene cloning experiments to study the target genes in yeast, E. coli and Arabidopsis heterologous systems. Upon confirmation of the effectiveness of these candidates, vectors containing the target genes will be constructed for transformation into rice. The new rice varieties produced will be tested under field conditions to assess their effectiveness at reducing or eliminating arsenic from the edible parts of the rice plant.
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| 5. |
- Nahar, Noor, et al.
(författare)
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Functional studies of AtACR2 gene putatively involved in accumulation, reduction and/or sequestration of arsenic species in plants
- 2017
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Ingår i: Biologia. - : Walter de Gruyter. - 0006-3088 .- 1336-9563. ; 72:5, s. 520-526
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Tidskriftsartikel (refereegranskat)abstract
- Food-based exposure to arsenic is a human carcinogen and can severely impact human health resulting in many cancerous diseases and various neurological and vascular disorders. This project is a part of our attempts to develop new varieties of crops for avoiding arsenic contaminated foods. For this purpose, we have previously identified four key genes, and molecular functions of two of these, AtACR2 and AtPCSl, have been studied based on both in silico and in vivo experiments. In the present study, a T-DNA tagged mutant, (SALK-143282C with mutation in AtACR2 gene) of Arabidopsis thaliana was studied for further verification of the function of AtACR2 gene. Semi-quantitative RT-PCR analyses revealed that this mutant exhibits a significantly reduced expression of the AtACR2 gene. When exposed to 100 μM of arsenate (AsV) for three weeks, the mutant plants accumulated arsenic approximately three times higher (778 μg/g d. wt.) than that observed in the control plants (235 μg/g d. wt.). In contrast, when the plants were exposed to 100 μM of arsenite (AsIII), no significant difference in arsenic accumulation was observed between the control and the mutant plants (535 μg/g d. wt. and 498 μg/g d. wt., respectively). Also, when arsenate and arsenite was measured separately either in shoots or roots, significant differences in accumulation of these substances were observed between the mutant and the control plants. These results suggest that AtACR2 gene is involved not only in accumulation of arsenic in plants, but also in conversion of arsenate to arsenite inside the plant cells. © 2017 Institute of Molecular Biology, Slovak Academy of Sciences.
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| 6. |
- Nahar, Noor, et al.
(författare)
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In silico and in vivo studies of an Arabidopsis thaliana gene, ACR2, putatively involved in arsenic accumulation in plants
- 2012
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Ingår i: Journal of Molecular Modeling. - : Springer. - 1610-2940 .- 0948-5023. ; 18:9, s. 4249-4262
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Tidskriftsartikel (refereegranskat)abstract
- Previously, our in silico analyses identified four candidate genes that might be involved in uptake and/or accumulation of arsenics in plants: arsenate reductase 2 (ACR2), phytochelatin synthase 1 (PCS1) and two multi-drug resistant proteins (MRP1 and MRP2) [Lund et al. (2010) J Biol Syst 18:223–224]. We also postulated that one of these four genes, ACR2, seems to play a central role in this process. To investigate further, we have constructed a 3D structure of the Arabidopsis thaliana ACR2 protein using the iterative implementation of the threading assembly refinement (I-TASSER) server. These analyses revealed that, for catalytic metabolism of arsenate, the arsenate binding-loop (AB-loop) and residues Phe-53, Phe-54, Cys-134, Cys-136, Cys-141, Cys-145, and Lys-135 are essential for reducing arsenate to arsenic intermediates (arsenylated enzyme-substrate intermediates) and arsenite in plants. Thus, functional predictions suggest that the ACR2 protein is involved in the conversion of arsenate to arsenite in plant cells. To validate the in silico results, we exposed a transfer-DNA (T-DNA)-tagged mutant of A. thaliana (mutation in the ACR2 gene) to various amounts of arsenic. Reverse transcriptase PCR revealed that the mutant exhibits significantly reduced expression of the ACR2 gene. Spectrophotometric analyses revealed that the amount of accumulated arsenic compounds in this mutant was approximately six times higher than that observed in control plants. The results obtained from in silico analyses are in complete agreement with those obtained in laboratory experiments.
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| 7. |
- Nahar, Noor, et al.
(författare)
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In silico and in vivo studies of molecular structures and mechanisms of AtPCS1 protein involved in binding arsenite and/or cadmium in plant cells
- 2014
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Ingår i: Journal of Molecular Modeling. - : Springer. - 1610-2940 .- 0948-5023. ; 20:3
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports a continuation of our previous research on the phytochelatin synthase1 (PCS1) gene involved in binding and sequestration of heavy metals or metalloids in plant cells. Construction of a 3D structure of the Arabidopsis thaliana PCS1 protein and prediction of gene function by employing iterative implementation of the threading assembly refinement (I-TASSER) revealed that PC ligands (3GC-gamma-glutamylcysteine) and Gln50, Pro53, Ala54, Tyr55, Cys56, Ile102, Gly161, His162, Phe163, Asp204 and Arg211 residues are essential for formation of chelating complex with cadmium (Cd²⁺) or arsenite (AsIII). This finding suggests that the PCS1 protein might be involved in the production of the enzyme phytochelatin synthase, which might in turn bind, localize, store or sequester heavy metals in plant cells. For validation of the in silico results, we included a T-DNA tagged mutant of Arabidopsis thaliana, SAIL_650_C12, (mutation in AtPCS1 gene) in our investigation. Furthermore, using reverse transcriptase PCR we confirmed that the mutant does not express the AtPCS1 gene. Mutant plants of SAIL_650_C12 were exposed to various amounts of cadmium (Cd²⁺) and arsenite (AsIII) and the accumulation of these toxic metals in the plant cells was quantified spectrophotometrically. The levels of Cd²⁺ and AsIII accumulation in the mutant were approximately 2.8 and 1.6 times higher, respectively, than that observed in the wild-type controlled plants. We confirmed that the results obtained in in silico analyses complement those obtained in in vivo experiments.
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| 8. |
- Nahar, Noor, et al.
(författare)
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Phytoremediation of arsenic from the contaminated soil using transgenic tobacco plants expressing ACR2 gene of Arabidopsis thaliana
- 2017
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Ingår i: Journal of plant physiology (Print). - : Elsevier. - 0176-1617 .- 1618-1328. ; 218, s. 121-126
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Tidskriftsartikel (refereegranskat)abstract
- We have cloned, characterized and transformed the AtACR2 gene (arsenic reductase 2) of Arabidopsis thaliana into the genome of tobacco (Nicotiana tabacum, var Sumsun). Our results revealed that the transgenic tobacco plants are more tolerant to arsenic than the wild type ones. These plants can grow on culture medium containing 200μM arsenate, whereas the wild type can barely survive under this condition. Furthermore, when exposed to 100μM arsenate for 35days the amount of arsenic accumulated in the shoots of transgenic plants was significantly lower (28μg/g d wt.) than that found in the shoots of non-transgenic controls (40μg/g d wt.). However, the arsenic content in the roots of transgenic plants was significantly higher (2400μg/g d. wt.) than that (2100μg/g d. wt.) observed in roots of wild type plants. We have demonstrated that Arabidopsis thaliana AtACR2 gene is a potential candidate for genetic engineering of plants to develop new crop cultivars that can be grown on arsenic contaminated fields to reduce arsenic content of the soil and can become a source of food containing no arsenic or exhibiting substantially reduced amount of this metalloid.
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| 9. |
- Nawani, Neelu, et al.
(författare)
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Status of metal pollution in rivers flowing through urban settlements at Pune and its effect on resident microflora
- 2016
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Ingår i: Biologia. - Bratislava : Springer. - 0006-3088 .- 1336-9563. ; 71:5, s. 494-507
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Tidskriftsartikel (refereegranskat)abstract
- This study illustrates the sporadic distribution of metals in fluvial systems flowing from catchments to urban settlements. This is a detailed study prognosticating the deteriorating quality of rivers at specific locations due to metal pollution. Heavy metals like cadmium, lead, nickel and mercury are prominent in industrial sector. Contour plots derived using spatial and temporal data could determine the focal point of metal pollution and its gradation. Metal values recorded were cadmium 157 mg/L, lead 47 mg/L, nickel 61 mg/L and mercury 0.56 mg/L. Prokaryote diversity was less in polluted water and it harboured metal tolerant bacteria, which were isolated from these polluted sites. Actinomycetes like Streptomyces and several other bacteria like Stenotrophomonas and Pseudomonas isolated from the polluted river sites exhibited changes in morphology in presence of heavy metals. This stress response offered remedial measures as Streptomyces were effective in biosorption of cadmium, nickel and lead and Stenotrophomonas and Pseudomonas were effective in the bioaccumulation of lead and cadmium. The amount of 89 mg of lead and 106 mg of nickel could be adsorbed on one gram of Streptomyces biomass-based biosorbent. Such biological remedies can be further explored to remove metals from polluted sites and from metal contaminated industrial or waste waters.
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| 10. |
- Rahman, Aminur, 1984-, et al.
(författare)
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Bioremediation of hexavalent chromium (VI) by a soil-borne bacterium, Enterobacter cloacae B2-DHA
- 2015
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Ingår i: Journal of Environmental Science and Health. Part A. - : Informa UK Limited. - 1093-4529 .- 1532-4117. ; 50:11, s. 1136-1147
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Tidskriftsartikel (refereegranskat)abstract
- Chromium and chromium containing compounds are discharged into the nature as waste from anthropogenic activities, such as industries, agriculture, forest farming, mining and metallurgy. Continued disposal of these compounds to the environment leads to development of various lethal diseases in both humans and animals. In this paper, we report a soil borne bacterium, B2-DHA that can be used as a vehicle to effectively remove chromium from the contaminated sources. B2-DHA is resistant to chromium with a MIC value of 1000 mu g mL(-1) potassium chromate. The bacterium has been identified as a Gram negative, Enterobacter cloacae based on biochemical characteristics and 16S rRNA gene analysis. TOF-SIMS and ICP-MS analyses confirmed intracellular accumulation of chromium and thus its removal from the contaminated liquid medium. Chromium accumulation in cells was 320 mu g/g of cells dry biomass after 120-h exposure, and thus it reduced the chromium concentration in the liquid medium by as much as 81%. Environmental scanning electron micrograph revealed the effect of metals on cellular morphology of the isolates. Altogether, our results indicate that B2-DHA has the potential to reduce chromium significantly to safe levels from the contaminated environments and suggest the potential use of this bacterium in reducing human exposure to chromium, hence avoiding poisoning.
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