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1.
Cupriavidus metallidurans strain CH34 is a β-Proteobacterium that thrives in low concentrations of heavy metals. The genetic determinants of resistance
to heavy metals are located on its two chromosomes, and are particularly abundant in the two megaplasmids, pMOL28 and pMOL30.
We explored the involvement of mobile genetic elements in acquiring these and others traits that might be advantageous in
this strain using genome comparison of Cupriavidus/Ralstonia strains and related β-Proteobacteria. At least eleven genomic islands were identified on the main replicon, three on pMOL28
and two on pMOL30. Multiple islands contained genes for heavy metal resistance or other genetic determinants putatively responding
to harsh environmental conditions. However, cryptic elements also were noted. New mobile genetic elements (or variations of
known ones) were identified through synteny analysis, allowing the detection of mobile genetic elements outside the bias of
a selectable marker. Tn4371-like conjugative transposons involved in chemolithotrophy and degradation of aromatic compounds were identified in strain
CH34, while similar elements involved in heavy metal resistance were found in Delftia acidovorans SPH-1 and Bordetella petrii DSM12804. We defined new transposons, viz., Tn6048 putatively involved in the response to heavy metals and Tn6050 carrying accessory genes not classically associated with transposons. Syntenic analysis also revealed new transposons carrying
metal response genes in Burkholderia xenovorans LB400, and other bacteria. Finally, other putative mobile elements, which were previously unnoticed but apparently common
in several bacteria, were also revealed. This was the case for triads of tyrosine-based site-specific recombinases and for
an int gene paired with a putative repressor and associated with chromate resistance. 相似文献
2.
Cupriavidus metallidurans CH34 has gained increasing interest as a model organism for heavy metal detoxification and for biotechnological purposes.
Resistance of this bacterium to transition metal cations is predominantly based on metal resistance determinants that contain
genes for RND (resistance, nodulation, and cell division protein family) proteins. These are part of transenvelope protein
complexes, which seem to detoxify the periplasm by export of toxic metal cations from the periplasm to the outside. Strain
CH34 contains 12 predicted RND proteins belonging to a protein family of heavy metal exporters. Together with many efflux
systems that detoxify the cytoplasm, regulators and possible metal-binding proteins, RND proteins mediate an efficient defense
against transition metal cations. To shed some light into the origin of genes encoding these proteins, the genomes of C. metallidurans CH34 and six related proteobacteria were investigated for occurrence of orthologous and paralogous proteins involved in metal
resistance. Strain CH34 was not much different from the other six bacteria when the total content of transport proteins was
compared but CH34 had significantly more putative transition metal transport systems than the other bacteria. The genes for
these systems are located on its chromosome 2 but especially on plasmids pMOL28 and pMOL30. Cobalt–nickel and chromate resistance
determinants located on plasmid pMOL28 evolved by gene duplication and horizontal gene transfer events, leading to a better
adaptation of strain CH34 to serpentine-like soils. The czc cobalt–zinc–cadmium resistance determinant, located on plasmid pMOL30 in addition copper, lead and mercury resistance determinants,
arose by duplication of a czcICAB core determinant on chromosome 2, plus addition of the czcN gene upstream and the genes czcD, czcRS, czcE
downstream of czcICBA. C. metallidurans apparently evolved metal resistance by horizontal acquisition and by duplication of genes for transition metal efflux, mostly
on the two plasmids, and decreased the number of uptake systems for those metals.
This paper is dedicated to Dr. Max Mergeay for a long time of cooperation, constructive competition and friendship. 相似文献
3.
4.
R. Nareshkumar R. Nagendran K. Parvathi 《World journal of microbiology & biotechnology》2008,24(8):1539-1546
Bioleaching of heavy metals from contaminated soil was carried out using indigenous sulfur oxidizing bacterium Acidithiobacillus thiooxidans. Experiments were carried out by varying sulfur/soil ratio from 0.03 to 0.33 to evaluate the optimum ratio for efficient
bioleaching of heavy metals from soil. The influence of sulfur/soil ratio on the bioleaching efficiency was assessed based
on decrease in pH, increase in oxidation–reduction potential, sulfate production and solubilization of heavy metals from the
soil. Decrease in pH, increase in oxidation–reduction potential and sulfate production was found to be better with the increase
in sulfur/soil ratio. While the final pH of the system with different sulfur/soil ratio was in the range of 4.1–0.7, oxidation
reduction potential varied from 230 to 629 mV; sulfate production was in the range of 2,786–8,872 mg/l. Solubilization of
chromium, zinc, copper, lead and cadmium from the contaminated soil was in the range of 11–99%. Findings of the study will
help to optimize the ratio of sulfur/soil to achieve effective bioleaching of heavy metals from contaminated soils. 相似文献
5.
6.
Nikoletta Hegedűs Tamás Emri Judit Szilágyi Zsolt Karányi István Nagy Michel J. Penninckx István Pócsi 《World journal of microbiology & biotechnology》2007,23(9):1339-1343
The glutathione (GSH) status and heavy metal tolerance were investigated in four Paxillus involutus strains isolated from different heavy-metal-polluted and non-polluted regions of Europe. The heavy metal burden in the habitats
did not affect significantly either the heavy metal (Cr2O72−, Cd2+, Hg2+, Pb2+, Zn2+, Cu2+) tolerance and accumulation or the GSH production of the strains tested. Exposures to heavy metals increased the intracellular
GSH concentrations in 12 from 24 experimental arrangements (four strains exposed to six heavy metals) independently of the
habitats of the strains. The importance of GSH in heavy metal tolerance (high MIC values, ability to accumulate heavy metals
and to grow in the presence of heavy metals) was thus demonstrated in this ectomycorrhizal fungus. 相似文献
7.
Cupriavidus metallidurans CH34 is a facultative chemolithotrophic bacterium that possesses two megaplasmids (pMOL28 and pMOL30) that confer resistance to eleven metals. The ability of Cupriavidus metallidurans CH34 to resist silver is described here. Electronic microscopy, energy-dispersive X-ray (EDX) and X-ray diffractometry (DRX)
observations revealed that C. metallidurans CH34 strongly associated silver with the outer membrane, under chloride chemical form. Using derivate strains of C. metallidurans CH34, which carried only one or no megaplasmid, we show that this resistance seems to be carried by pMOL30. 相似文献
8.
为探讨金毛狗[Cibotium barometz(L.) J. Sm.]对重金属的富集能力,在广东省选取6个样点(南岭、南昆山、白云山、大岭山、梧桐山、西樵山)采集金毛狗的叶片、根状茎和根际土壤,采用ICP-MS测定9种重金属元素(Cr、Mn、Ni、Cu、Zn、As、Cd、Hg、Pb)的含量。结果表明,样地土壤已受到不同程度的重金属污染,土壤中Cd和Hg含量均高于广东省土壤背景值,分别为背景值的1.61~4.82倍和4.74~11.79倍。西樵山土壤中Cd含量最大,南岭土壤中Hg含量最大。在9种元素中,金毛狗对Hg的转运系数最高,达4.8,对Cd的富集系数最高,达2.2,Cu和Cd元素的转运系数和富集系数均大于1。这说明金毛狗对重金属元素的富集能力较弱而转运能力较强。 相似文献
9.
Heavy metal-resistant bacteria as extremophiles: molecular physiology and biotechnological use of Ralstonia sp. CH34 总被引:2,自引:0,他引:2
Nies DH 《Extremophiles : life under extreme conditions》2000,4(2):77-82
In contrast to thermophilic or psychrophilic organisms, heavy metal-resistant bacteria do not supply enzymes that are active
under harsh conditions, but are themselves tools for the evaluation and remediation of heavy metal-contaminated environments.
Ralstonia sp. CH34 is a gram-negative bacterium with a remarkable set of resistance determinants, allowing this bacterium to live in
extreme environments that are heavily contaminated with toxic metal ions. These heavy metal ions are mostly detoxified by
inducible ion efflux systems that reduce the intracellular concentration of a given ion by active export. Because all metal
resistance determinants in this bacterium are inducible, their regulatory systems can be used to develop biosensors that measure
the biologically important concentrations of heavy metals in an environment. Resistance based on metal ion efflux detoxifies
only the cytoplasm of the respective cell. Therefore, this resistance mechanism cannot be used directly to develop biotechnological
procedures; however, metal ion efflux can protect a cell in a metal-contaminated environment. Thus, the cell can be enabled
to mediate biochemical reactions such as precipitation of heavy metals with the carbon dioxide produced during growth or degradation
of xenobiotics.
Received: July 11, 1999 / Accepted: December 27, 1999 相似文献
10.
Lesage E Meers E Vervaeke P Lamsal S Hopgood M Tack FM Verloo MG 《International journal of phytoremediation》2005,7(2):143-152
High biomass producing plant species, such as Helianthus annuus, have potential for removing large amounts of trace metals by harvesting the aboveground biomass if sufficient metal concentrations in their biomass can be achieved However, the low bioavailability of heavy metals in soils and the limited translocation of heavy metals to the shoots by most high biomass producing plant species limit the efficiency of the phytoextraction process. Amendment of a contaminated soil with ethylene diamine tetraacetic acid (EDTA) or citric acid increases soluble heavy metal concentrations, potentially rendering them more available for plant uptake. This article discusses the effects of EDTA and citric acid on the uptake of heavy metals and translocation to aboveground harvestable plant parts in Helianthus annuus. EDTA was included in the research for comparison purposes in our quest for less persistent alternatives, suitable for enhanced phytoextraction. Plants were grown in a calcareous soil moderately contaminated with Cu, Pb, Zn, and Cd and treated with increasing concentrations of EDTA (0.1, 1, 3, 5, 7, and 10 mmol kg(-1) soil) or citric acid (0.01, 0.05, 0.25, 0.442, and 0.5 mol kg(-1) soil). Heavy metal concentrations in harvested shoots increased with EDTA concentration but the actual amount of phytoextracted heavy metals decreased at high EDTA concentrations, due to severe growth depression. Helianthus annuus suffered heavy metal stress due to the significantly increased bioavailable metal fraction in the soil. The rapid mineralization of citric acid and the high buffering capacity of the soil made citric acid inefficient in increasing the phytoextracted amounts of heavy metals. Treatments that did not exceed the buffering capacity of the soil (< 0.442 mol kg(-1) soil) did not result in any significant increase in shoot heavy metal concentrations. Treatments with high concentrations resulted in a dissolution of the carbonates and compaction of the soil. These physicochemical changes caused growth depression of Helianthus annuus. EDTA and citric acid added before sowing of Helianthus annuus did not appear to be efficient amendments when phytoextraction of heavy metals from calcareous soils is considered. 相似文献
11.
Junkang Guo Shirong Tang Xuehai Ju Yongzhen Ding Shangqiang Liao Ningning Song 《World journal of microbiology & biotechnology》2011,27(12):2835-2844
Batch experiments were designed to characterize a multiple metal resistant bacterium Burkholderia sp. D54 isolated from metal contaminated soils in the Dabaoshan Mine in South China, and a follow-up experiment was conducted
to investigate the effects of inoculating the isolate on plant growth and metal uptake by Sedum alfredii Hance grown on soils collected from a heavily contaminated paddy field in Daxing County, Guangxi Zhuang Automounous Region,
Southwest China. Our experiments showed that strain D54 produced indole acetic acid (IAA), siderophores, 1-aminocyclopropane-1-carboxylate
(ACC) deaminase, and solubilizing inorganic phosphate and solubilized insoluble metal bearing minerals. Bacterial inoculation
significantly enhanced S. alfredii biomass production, and increased both shoot and root Cd concentration, but induced little variation in root/shoot Pb concentration
and shoot Zn concentration. Despite this, the total shoot and root uptake of Cd, Pb and Zn in S. alfredii inoculated with D54 increased greatly compared to the non-inoculated controls. It was concluded that inoculation with strain
D54 could help S. alfredii grow better on metal contaminated soils, produce more biomass, and remove more metals from soil, which implies improved efficiency
of phytoextraction from metal contaminated soil. The knowledge gained from the present experiments constitutes an important
advancement in understanding of the interaction between plant growth-promoting bacteria and hyperaccumulators with regard
to plant ability to grow and remove the multiple heavy metals from soils. 相似文献
12.
Numerous microbial habitats are strongly influenced by elevated levels of heavy metals. This type of habitat has developed
either due to ore mining and metal processing or by pedogenesis above metal-rich base rocks. Most actinobacteria are soil-borne
microbes with a remarkable capability for the synthesis of a broad variety of biologically active secondary metabolites. One
major obstacle in identifying secondary metabolites, however, is the known phenomenon of sleeping gene clusters which are
present, but silent under standard screening conditions. Here, we proceed to show that sleeping gene clusters can be awakened
by the induction in heavy metal stress. Both, a chemical and a biological screening with extracts of supernatant and biomass
of 10 strains derived from metal contaminated and non-contaminated environments was carried out to assay the influence of
heavy metals on secondary metabolite patterns of metal tolerant actinobacteria. Metabolite patterns of cultures grown in complex
and minimal media were compared to nickel (or cadmium) spiked parallels. Extracts of some strains grown in the presence of
a metal salt displayed intense antibiosis against Escherichia coli, Mycobacterium smegmatis, Staphylococcus aureus and Candida albicans. Contrarily to the widely held opinion of metals as hindrance in secondary metabolism, metals thus can induce or enhance
synthesis of possibly potent and medically relevant metabolites in metal tolerant strains. Hence, re-screening of existing
strain libraries as well as identification of new strains from contaminated areas are valid strategies for the detection of
new antibiotics in the future. 相似文献
13.
14.
Aly E. Abo-amer Magdy A. Abu-gharbia El-Sayed M. Soltan Walaa M. Abd El-Raheem 《Geomicrobiology journal》2014,31(7):551-561
Pollution of soil with heavy metals, herbicides, antibiotics and other chemicals is known to have a negative effect on microbial activities. Therefore, the aim of this study was to isolate cultures of Azotobacter sp. from polluted and unpolluted soils and to study the effect of these pollutants on their growth. A total of 120 Azotobacter sp. were isolated from soils irrigated with wastewater (contaminated soils) and groundwater (uncontaminated soils). These isolates were screened for resistance to heavy metals, herbicide and antibiotics. Also, the soils from which the cultures were isolated were analyzed for the concentrations of Zn2+, Cd2+, Cu2+, Pb2+ and Mn2+ they contained. Contaminated soil showed high levels of heavy metals as compared to uncontaminated soil. The size of the Azotobacter population in contaminated soil was lower than that in uncontaminated soil. Of the Azotobacter isolates, 64 that were recovered from contaminated soil exhibited high resistance to heavy metals (Hg2+, Cd2+, Cu2+, Cr3+, Co2+, Ni2+, Zn2+ and Pb2+) and herbicide 2,4-D compared to 56 isolates from uncontaminated soil. Also, isolates from contaminated soil showed high resistance to chloramphenicol, nitrofurantoin and co-trimoxazole compared to those isolated from uncontaminated soil. The majority of Azotobacter isolates from contaminated soil showed multiple-resistance to different metal ions and antibiotics. All isolates failed to grow at pH less than 6. Salt concentration (5%) was found to be inhibitory to all isolates. The most potent isolates from contaminated soil that showed multiresistance to all substances tested were identified on the basis of morphological and biochemical characteristics, and 16S rRNA as A. chroococcum. These resistant isolates could be employed in contaminated soils and/or bioremediation. 相似文献
15.
上海地区绿化树种重金属污染防护特性的研究 总被引:14,自引:2,他引:14
通过测定土壤样品的重金属含量,调查了上海七宝镇污染水系两侧与上海宝钢集团厂区的重金属污染状况。结果表明,在污染水系两侧重金属含量较对照稍高,而上海宝钢厂区各样点土壤重金属含量明显高于对照,存在较严重的污染.同时在这两处重金属污染地带观察记录了绿化树种的生长状况,采集植物样品以ICP仪进行树木样品的重金属含量分析,综合两方面数据对近20种常见绿化树种的重金属污染的防护特性进行了比较研究.结果表明,法国冬青、紫薇、木芙蓉、女贞和龙柏等植物种类富集重金属能力较强,且生长状况较为良好,最适于作为重金属污染厂区的生态防护绿化的主要树种;而蚊母、夹竹桃和石楠等植物种类虽然富集重金属能力较低,但有较强的耐性,能良好生长。也适于作为污染区绿化美化树种。 相似文献
16.
Summary Small plots were amended in 1976 or 1978 with four kinds of sewage sludge. The sludges represented samples considered to be
relatively free of heavy metals as well as sludges highly contaminated with heavy metals. Sludges were added to a silt loam
soil at rates of 224 or 448 Mgha−1. The soils were maintained at a high or low pH regime. In 1984, soybeans (Glycine max L. Merril. var. ‘Clark’) were planted and grown to the R4 stage. After harvest, roots were removed from the soil, washed,
and examined for VA mycorrhizal infection.
It was found that the heavy metal content of the sludge alone was generally not related to determining the extent of mycorrhizal
infection. A heat treated sludge, high in heavy metals, exhibited the highest degree of mycorrhizal infection when the soil
was maintained at a pH of 6.2. With this treatment, 52% of the root segments examined were infected by mycorrhiza. When the
same sludge was added to a soil with a slightly lower pH (5.7) none of the roots examined were infected by mycorrhiza. When
soybean roots were examined from soils that received no sludge and were maintained at either a low (5.6) or high (6.2) pH,
there was no significant difference in mycorrhizal infection between the pH regimes. These results therefore indicate that
sewage sludge may inhibit mycorrhizal infection if the sludge contains a high concentration of heavy metals and the sludge
is applied to the soil with a low pH.
Scientific Article No. A-4093 and Contribution No 7078 of the Maryland Agric. Exp. Stn., Dept. of Agronomy, University of
Maryland, College Park, MD 20742. 相似文献
17.
The effect of heavy metal deposition onto soil from a copper smelter on lipid peroxidation and antioxidant enzyme activity
in the fine roots of two poplars (Populus nigra L. and Populus deltoides Bartr. ex Marsch) was analyzed. The subjects were mature trees growing in real environments. In both analyzed species, heavy
metals stimulated the overproduction of free radicals in fine roots (measured as malondialdehyde level), which was directly
proportional to advancing senescence. In young fine roots, heavy metals caused a decrease in guaiacol peroxidase activity
and presumably disturbed the lignification process. Catalase was highly sensitive to the presence of heavy metals in the soil.
In contrast, ascorbate peroxidase and glutathione reductase activities were unaffected by heavy metals. In the case of superoxide
dismutase, a clear increase in enzyme activity was observed only in P. nigra under drought conditions, whereas it was inhibited in polluted stands. 相似文献
18.
Atul Bhargava Sudhir Shukla Jatin Srivastava Nandita Singh Deepak Ohri 《Acta Physiologiae Plantarum》2008,30(1):111-120
Leaf samples were collected from 40 accessions of Chenopodium spp. and assessed for six heavy metals (Fe, Zn, Cu, Ni, Cr and Cd) accumulation to explore the use of Chenopodium for phytoextraction of heavy metals. The results suggest that Chenopodium spp. have the ability to accumulate large quantities of heavy metals in the leaf tissues even when they are present in low
concentrations in the soil. C. quinoa is a better accumulator of Ni, Cr and Cd than the rest of the species, while C. album accessions are good copper accumulators. Bioconcentration factor for chromium ranged from 0.36 (C. album “Chandanbathua”) to 6.57 (C. quinoa Ames 13719) with 13 accessions of C. quinoa scoring above the mean value. High heritability coupled with high genetic advance was recorded for Ni, Cr and Cd, which indicated
a major role of additive gene action in the inheritance of these characters. Zinc showed significant positive association
with iron (0.351**), nickel (0.659**), chromium (0.743**) and cadmium (0.288**). Nickel was significantly and negatively associated
with copper (−0.663**), while it was positively and significantly correlated with chromium (0.682**) and cadmium (0.461**).
Considering the accumulation efficiency of Chenopodium spp. with respect to heavy metals, this genus should be further explored for decontamination of metal polluted soils, with
plant breeding playing an important role in evolving new plant types with higher capacity of heavy metal accumulation. 相似文献
19.
Industrialization, urbanization and increased vehicular traffic have resulted in increased contamination of our environment by heavy metals. The long persistence of heavy metals in nature has in turn resulted in development of metal resistant microbial strains. These strains are minimizing heavy metals toxicity, either by metal complexation or precipitation and other mechanisms. Characterization of fungal diversity was done in contaminated soil of the Wazirpur industrial area throughout the year. In this area highly acidic hazardous solid waste produced high concentration of heavy metals (Ni, Cu, Cr, Fe, Mn). Nickel toxicity is a major environmental concern. Due to long persistence of this waste in the environment without any treatment, many fungal isolates from the surrounding environment settle on the upper surface of waste. Few of them are capable of growing in the toxic conditions. More than 20 strains were isolated, most of them belonging to species of Aspergillus, Penicillium, Fusarium and Mucor genera. Seasonal variation in fungal diversity was significant. Four filamentous fungal isolates were found to be resistant for nickel (II) and a strain of Papulaspora sepedonoides reported first time for bioremediation of Ni (II) in this investigation, which is absorbing 62.33 μmol Ni gr?1. These fungal isolates showed a high level (100–10000 mg kg?1) of resistance for Ni (II) salt and removing Ni (II) from solution. Metal uptake varied with fungi. The toxicity also was influenced by different factors like pH and composition of growth medium. 相似文献
20.
The weathering of volcanic minerals makes a significant contribution to the global silicate weathering budget, influencing carbon dioxide drawdown and long‐term climate control. Basalt rocks may account for over 30% of the global carbon dioxide drawdown in silicate weathering. Micro‐organisms are known to play a role in rock weathering yet the genomics and genetics of biological rock weathering are unknown. We apply DNA microarray technology to determine putative genes involved in weathering using the heavy metal‐resistant organism, Cupriavidus metallidurans CH34; in particular we investigate the sequestering of iron. The results show that the bacterium does not depend on siderophores. Instead, the up‐regulation of porins and transporters which are employed concomitantly with genes associated with biofilm formation suggests that novel passive and active iron uptake systems are involved. We hypothesize that these mechanisms induce rock weathering by changes in chemical equilibrium at the microbe–mineral interface, reducing the saturation state of iron. We also demonstrate that low concentrations of metals in the basalt induce heavy metal‐resistant genes. Some of the earliest environments on the Earth were volcanic. Therefore, these results not only elucidate the mechanisms by which micro‐organisms might have sequestered nutrients on the early Earth but also provide an explanation for the evolution of multiple heavy metal resistance genes long before the creation of contaminated industrial biotopes by human activity. 相似文献