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Bacterial mechanisms for Cr(VI) resistance and reduction: an overview and recent advances 总被引:1,自引:0,他引:1
Munees Ahemad 《Folia microbiologica》2014,59(4):321-332
Chromium pollution is increasing incessantly due to continuing industrialization. Of various oxidation states, Cr6+ is very toxic due to its carcinogenic and mutagenic nature. It also has deleterious effects on different microorganisms as well as on plants. Many species of bacteria thriving in the Cr6+-contaminated environments have evolved novel strategies to cope with Cr6+ toxicity. Generally, decreased uptake or exclusion of Cr6+ compounds through the membranes, biosorption, and the upregulation of genes associated with oxidative stress response are some of the resistance mechanisms in bacterial cells to overcome the Cr6+ stress. In addition, bacterial Cr6+ reduction into Cr3+ is also a mechanism of specific significance as it transforms toxic and mobile chromium derivatives into reduced species which are innocuous and immobile. Ecologically, the bacterial trait of reductive immobilization of Cr6+ derivatives is of great advantage in bioremediation. The present review is an effort to underline the bacterial resistance and reducing mechanisms to Cr6+ compounds with recent development in order to garner a broad perspective. 相似文献
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In this study, a total of 50 rhizobial isolates were recovered from the root nodules of greengram plants. Of the 50 isolates,
9 bradyrhizobial strains namely, MRM1, MRM2, MRM3, MRM4, MRM5, MRM6, MRM7, MRM8, and MRM9, exhibiting a higher tolerance levels
of 600, 800, 1,200, 1,000, 1,000, 1,600, 1,400, 1,400, and 1,000 μg ml−1, respectively, to triazole fungicide tebuconazole (chromatographically pure) were selected and tested for plant growth-promoting
activities. Generally, the rhizobial strain with maximum fungicide-tolerance ability produced higher amounts of plant growth-promoting
substances. Among the nine bacterial strains, Bradyrhizobium strain MRM6 was preferably selected due to its ability to tolerate tebuconazole maximally (up to 1,600 μg ml−1) on minimal salt agar medium. In addition, the strain MRM6 grew well in minimal salts medium supplemented with 100 (recommended),
200 (two times of the recommended), and 300 μg tebuconazole l−1 (three times of the recommended rate) and synthesized highest amounts of plant growth-promoting substances like indole acetic
acid, siderophores, exopolysaccharides, hydrogen cyanate, and ammonia, both in the absence and presence of 100, 200, and 300 μg l−1 of tebuconazole. Following these properties, the strain MRM6 was used as inoculant and the inoculated greengram plants was
raised in soils treated separately with recommended, two and three times the recommended dose of tebuconazole. Generally,
tebuconazole at recommended and the higher rates decreased biomass, nodulation, nutrient-uptake, and grain yield of uninoculated
greengram plants. Interestingly, Bradyrhizobium sp. (vigna) strain MRM6 when used with any concentration of tebuconazole, significantly increased the measured phyto-chemical-parameters
of greengram plants when compared with those grown in soils treated exclusively (without inoculant) with tebuconazole. This
study inferred that the strain MRM6 of Bradyrhizobium sp. (vigna) was compatible with tebuconazole and may be co-inoculated with this fungicide for enhancing the production of legumes especially
greengram in soils poisoned with fungicides. 相似文献
3.
This study examines the effect of four herbicides, quizalafop-p-ethyl, clodinafop, metribuzin and glyphosate, on plant growth promoting activities like phosphate solubilization, siderophores,
indole acetic acid, exo-polysaccharides, hydrogen cyanide and ammonia production by herbicide tolerant Klebsiella sp. strain PS19. The strain was isolated from mustard rhizosphere. The selected herbicides were applied two to three times
at the recommended rates. Klebsiella sp. strain PS19 tolerated a concentration of 1600 μg/ml each of quizalafop-p-ethyl and clodinafop, and 3200 and 2800 μg/ml of metribuzin and glyphosate, respectively. The activities of Klebsiella sp. strain PS19 observed under in vitro environment were persistent in the presence of all herbicides at lower rates. The
plant growth promoting activities even-though decreased regularly, but was not lost completely, as the concentration of each
herbicide was increased from the recommended to three times of higher doses. Among all herbicides, quizalafop-p-ethyl, generally, showed maximum toxicity to plant growth promoting activities of Klebsiella sp. strain PS19. As an example, 40, 80 and 120 μg/l of quizalafop-p-ethyl added to liquid culture Pikovskaya medium, decreased phosphate solubilizing activity of strain PS19 by 93, 95 and 97%,
respectively over untreated control. The study revealed that the higher rates of herbicides though decreased the plant growth
promoting activity but it did not completely inhibit the metabolic activities of strain PS19. The herbicide tolerance together
with growth promoting activities observed under herbicide stress suggests that Klebsiella sp. strain PS19 could be used as bacterial preparation for facilitating the growth and yields of crops even in soils polluted
with herbicides. 相似文献
4.
The goal of this study was to identify lentil-specific rhizobial strains with the ability to tolerate fungicide and synthesize
plant growth regulators even in soils contaminated with fungicides. A fungicide-tolerant and plant-growth-promoting rhizobial
strain was used to assess its impact on lentil grown in fungicide-treated soils. The tebuconazole-tolerant Rhizobium sp. strain MRL3 produced plant-growth-promoting substances when grown in the presence and the absence of tebuconazole. Tebuconazole
at the recommended and two and three times the recommended doses decreased consistently the dry biomass, symbiotic properties,
nutrient uptake, and seed yields of lentil plants. In contrast, the fungicide-tolerant strain MRL3 significantly increased
the measured parameters when lentil was grown in soils treated with varying concentrations of tebuconazole compared to uninoculated
plants. As an example, strain MRL3 with 100 μg tebuconazole/kg soil significantly increased the root nitrogen, shoot nitrogen,
root phosphorus, shoot phosphorus, and seed yield by 31, 10, 41, 21, and 117%, respectively, compared to the uninoculated
plants grown in soil treated solely with 100 μg tebuconazole/kg soil. In conclusion, the Rhizobium strain MRL3 may be applied as biofertilizer to enhance the performance of lentil plants in fungicide-applied soils. 相似文献
5.
The study was designed to assess the effect of selected pesticides (metribuzin, glyphosate, imidacloprid, thiamethoxam, hexaconazole, metalaxyl and kitazin) at the recommended and higher rates on plant growth promoting activities of Pseudomonas aeruginosa strain PS1 isolated from mustard (Brassica compestris) rhizosphere. The strain PS1 was specifically chosen owing to its substantial tolerance against pesticides, phosphate solubilization and considerable production of indole acetic acid, siderophores, exo-polysaccharides, HCN and ammonia. Plant growth promoting traits of the strain PS1 decreased consistently as the concentrations of each pesticide was increased from the recommended dose to the higher ones. Generally, the maximum toxicity to plant growth promoting traits was displayed by pesticides at three times the recommended field rate. However, the effect on the plant growth promoting activities of the P. aeruginosa strain PS1 at the recommended dose of each pesticide was less hazardous. This study revealed an additional aspect of the toxicological mechanisms of the pesticides through which they suppress the plant growth. 相似文献
6.
Kai Hung Tiong Nafees Ahemad Mohammed Yunus Beow Chin Yiap Eng Lai Tan Rusli Ismail Chin Eng Ong 《PloS one》2014,9(1)
Human cytochrome P450 2A6 (CYP2A6) is a highly polymorphic isoform of CYP2A subfamily. Our previous kinetic study on four CYP2A6 allelic variants (CYP2A6*15, CYP2A6*16, CYP2A6*21 and CYP2A6*22) have unveiled the functional significance of sequence mutations in these variants on coumarin 7-hydroxylation activity. In the present study, we further explored the ability of a typical CYP2A6 inhibitor, 8-methoxypsoralen (8-MOP), in inhibition of these alleles and we hypothesized that translational mutations in these variants are likely to give impact on 8-MOP inhibitory potency. The CYP2A6 variant and the wild type proteins were subjected to 8-MOP inhibition to yield IC50 values. In general, a similar trend of change in the IC50 and Km values was noted among the four mutants towards coumarin oxidation. With the exception of CYP2A6*16, differences in IC50 values were highly significant which implied compromised interaction of the mutants with 8-MOP. Molecular models of CYP2A6 were subsequently constructed and ligand-docking experiments were performed to rationalize experimental data. Our docking study has shown that mutations have induced enlargement of the active site volume in all mutants with the exception of CYP2A6*16. Furthermore, loss of hydrogen bond between 8-MOP and active site residue Asn297 was evidenced in all mutants. Our data indicate that the structural changes elicited by the sequence mutations could affect 8-MOP binding to yield differential enzymatic activities in the mutant CYP2A6 proteins. 相似文献
7.
This study was designed to explore beneficial plant-associated rhizobacteria exhibiting substantial tolerance against fungicide tebuconazole vis-à-vis synthesizing plant growth regulators under fungicide stressed soils and to evaluate further these multifaceted rhizobacteria for protection and growth promotion of greengram [Vigna radiata (L.) Wilczek] plants against phytotoxicity of tebuconazole. Tebuconazole-tolerant and plant growth promoting bacterial strain PS1 was isolated from mustard (Brassica compestris) rhizosphere and identified as Pseudomonas aeruginosa following 16S rRNA gene sequencing. The P. aeruginosa strain PS1 solubilized phosphate significantly and produced indole acetic acid, siderophores, exo-polysaccharides, hydrogen cyanide and ammonia even under tebuconazole stress. Generally, tebuconazole at the recommended, two and three times the recommended field rate adversely affected the growth, symbiosis, grain yield and nutrient uptake in greengram in a concentration dependent manner. In contrast, the P. aeruginosa strain PS1 along with tebuconazole significantly, increased the growth parameters of the greengram plants. The inoculant strain PS1 increased appreciably root nitrogen, shoot nitrogen, root phosphorus, shoot phosphorus, and seed yield of greengram plants at all tested concentrations of tebuconazole when compared to the uninoculated plants treated with tebuconazole. The results suggested that the P. aeruginosa strain PS1, exhibiting novel plant growth regulating physiological features, can be applied as an eco-friendly and plant growth catalyzing bio-inoculant to ameliorate the performance of greengram in fungicide stressed soils. 相似文献
8.
This study was designed to identify rhizobial strains specific to greengram expressing higher tolerance against insecticides,
fipronil and pyriproxyfen, and synthesizing plant growth regulators even amid insecticide-stress. Of the 50 bradyrhizobial
isolates, the Bradyrhizobium sp. strain MRM6 showed tolerance up to 1,600 μg mL−1 against each of fipronil and pyriproxyfen. The tolerant Bradyrhizobium sp. (vigna) produced plant growth promoting substances in substantial amounts, both in the presence and absence of insecticides. The
strain MRM6 was further used to investigate its impact on greengram grown in soils treated with 200 (the recommended dose),
400 and 600 μg kg−1 soil of fipronil and 1,300 (the recommended dose), 2,600 and 3,900 μg kg−1 soil of pyriproxyfen. Fipronil at 600 μg kg−1 soils and pyriproxyfen at 3,900 μg kg−1 soils had greatest toxic effects and decreased plant biomass, symbiotic efficiency, nutrient uptake and seed yield of greengram
plants. The Bradyrhizobium sp. (vigna) inoculant when used with fipronil and pyriproxyfen significantly increased the measured parameters compared to the plants
grown in soils treated solely with the same concentration of each insecticide. This study inferred that the Bradyrhizobium sp. (vigna) strain MRM6 may be exploited as bio-inoculant to increase the productivity of greengram exposed to insecticide-stressed
soils. 相似文献
9.
Tan Ji Tan Pui-Ling Poong Sze-Wan Brakel Janina Gachon Claire Brodie Juliet Sade Ahemad Kassim Azhar Lim Phaik-Eem 《Journal of applied phycology》2022,34(5):2719-2733
Journal of Applied Phycology - The region of Eastern Sabah, Malaysia, harbours a rich diversity of eucheumatoid (i.e. Kappaphycus and Eucheuma spp.) algae. The global cultivation of this group of... 相似文献
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