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1.
The initial risk assessment for the East Fork Poplar Creek (EFPC) floodplain in Oak Ridge, Tennessee, a superfund site heavily contaminated with mercury, was based on a reference dose for mercuric chloride. Mercuric chloride, however, is a soluble mercury compound not expected to be present in the floodplain, which is frequently saturated with water. Previous investigations had suggested mercury in the EFPC floodplain was less soluble and therefore potentially less bioavailable than mercuric chloride, possibly making the results of the risk assessment unduly conservative. A bioaccessibility study, designed to measure the amount of mercury available for absorption in a child's digestive tract (the most critical risk pathway endpoint), was performed on 20 soils from the EFPC floodplain. The average bioac-cessible mercury for the 20 soils was 5.3%, compared with 100% of the mercuric chloride subjected to the same conditions. The alteration of the procedure to more closely mimic conditions in the digestive tract did not significantly change the results. Therefore, the use of a reference dose for mercuric chloride at EFPC, and potentially at other mercury-contaminated sites, without incorporating a corresponding bioavailability adjustment factor may overestimate the risk posed by the site.  相似文献   

2.
Zeng  Weimin  Li  Fang  Wu  Chenchen  Yu  Runlan  Wu  Xueling  Shen  Li  Liu  Yuandong  Qiu  Guanzhou  Li  Jiaokun 《Bioprocess and biosystems engineering》2020,43(1):153-167

Heavy metal resistant bacteria are of great interest because of their potential use in bioremediation. Understanding the survival and adaptive strategies of these bacteria under heavy metal stress is important for better utilization of these bacteria in remediation. The objective of this study was to investigate the role of bacterial extracellular polymeric substance (EPS) in detoxifying against different heavy metals in Bacillus sp. S3, a new hyper antimony-oxidizing bacterium previously isolated from contaminated mine soils. The results showed that Bacillus sp. S3 is a multi-metal resistant bacterial strain, especially to Sb(III), Cu(II) and Cr(VI). Toxic Cd(II), Cr(VI) and Cu(II) could stimulate the secretion of EPS in Bacillus sp. S3, significantly enhancing the adsorption and detoxification capacity of heavy metals. Both Fourier transform infrared spectroscopy (FTIR) and three-dimensional excitation–emission matrix (3D-EEM) analysis further confirmed that proteins were the main compounds of EPS for metal binding. In contrast, the EPS production was not induced under Sb(III) stress. Furthermore, the TEM–EDX micrograph showed that Bacillus sp. S3 strain preferentially transported the Sb(III) to the inside of the cell rather than adsorbed it on the extracellular surface, indicating intracellular detoxification rather than extracellular EPS precipitation played an important role in microbial resistance towards Sb(III). Together, our study suggests that the toxicity response of EPS to heavy metals is associated with difference in EPS properties, metal types and corresponding environmental conditions, which is likely to contribute to microbial-mediated remediation.

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3.
Genotoxic responses (chromosomal damage, DNA strandbreakage) of redbreast sunfish (Lepomis auritis)populations exposed to industrial effluent andmutagenicity of the associated sediments weredetermined in order to compare them to changes incommunity structure. Data were collected from areference stream and East Fork Poplar Creek (EFPC), afirst-order stream which originates on the grounds ofthe Department of Energy Y-12 Plant at Oak Ridge, TN. This stream is contaminated with mercury, PCBs, andnumerous other compounds. Previous studies have shownthat sediment contaminant concentrations, as well asphysiological biomarker responses of the local fishpopulations, are highest at the headwaters of EFPC anddecrease with increasing distance from the DOEfacility as contaminant loading decreases. Chromosomal damage was measured by flow cytometry – asreflected by variation in cellular DNA content – andstrand breakage was determined by agarose gelelectrophoresis using blood as the source of DNA. Mutagenicity was determined by theSalmonella/microsome assay using organic solventextracts of sediment surface samples. Community levelresponses included community diversity and percentpollution-tolerant species. Biomarker responses andmutagenicity were found to be highest at theheadwaters of EFPC, and tended to decrease withincreasing distance from the effluent. In general,biomarker responses appeared to be correlated withmutagenicity of the sediment, and both of theserelated to fish community disturbance and level ofstream contamination. Because responses at severallevels of biological organization show similarpatterns of downstream effects, this suggests thatthere may be a causal relationship betweencontamination and biological effects.  相似文献   

4.
Cupriavidus sp. strain BIS7 is a Malaysian tropical soil bacterium that exhibits broad heavy-metal resistance [Co(II), Zn(II), Ni(II), Se(IV), Cu(II), chromate, Co(III), Fe(II), and Fe(III)]. It is particularly resistant to Fe(II), Fe(III), and Zn(II). Here we present the assembly and annotation of its genome.  相似文献   

5.
The contamination of groundwater with mercury (Hg) is an increasing problem worldwide. Yet, little is known about the interactions of Hg with microorganisms and their processes in subsurface environments. We tested the impact of Hg on denitrification in nitrate reducing enrichment cultures derived from subsurface sediments from the Oak Ridge Integrated Field Research Challenge site, where nitrate is a major contaminant and where bioremediation efforts are in progress. We observed an inverse relationship between Hg concentrations and onset and rates of denitrification in nitrate enrichment cultures containing between 53 and 1.1 μM of inorganic Hg; higher Hg concentrations increasingly extended the time to onset of denitrification and inhibited denitrification rates. Microbial community complexity, as indicated by terminal restriction fragment length polymorphism (tRFLP) analysis of the 16S rRNA genes, declined with increasing Hg concentrations; at the 312 nM Hg treatment, a single tRFLP peak was detected representing a culture of Bradyrhizobium sp. that possessed the merA gene indicating a potential for Hg reduction. A culture identified as Bradyrhizobium sp. strain FRC01 with an identical 16S rRNA sequence to that of the enriched peak in the tRFLP patterns, reduced Hg(II) to Hg(0) and carried merA whose amino acid sequence has 97 % identity to merA from the Proteobacteria and Firmicutes. This study demonstrates that in subsurface sediment incubations, Hg may inhibit denitrification and that inhibition may be alleviated when Hg resistant denitrifying Bradyrhizobium spp. detoxify Hg by its reduction to the volatile elemental form.  相似文献   

6.

Background  

Enterobacter sp. YSU is resistant to several different heavy metal salts, including selenite. A previous study using M-9 minimal medium showed that when the selenite concentration was 100,000 times higher than the sulfate concentration, selenite entered Escherichia coli cells using two pathways: a specific and a non-specific pathway. In the specific pathway, selenite entered the cells through a yet to be characterized channel dedicated for selenite. In the non-specific pathway, selenite entered the cells through a sulfate permease channel. Addition of L-cystine, an L-cysteine dimer, appeared to indirectly decrease selenite import into the cell through the non-specific pathway. However, it did not affect the level of selenite transport into the cell through the specific pathway.  相似文献   

7.
In this study, among a collection of heavy metals resistant endophytic bacterial strains isolated from aquatic hyperaccumulator plant (Eichhornia crassipes), one plant growth promoting endophytic bacteria (PGPE), SVUB4 was selected for its ability to utilize 1-aminocyclopropane-1-carboxylic acid (ACC) as the sole N source and accumulate different heavy metals. The SVUB4 strain was characterized as Enterobacter sp. on the basis of its 16S rDNA sequences. Assessment of the parameters of plant growth promotion revealed the intrinsic ability of the strain for the production of IAA, siderophore and solubilization of insoluble phosphate. Furthermore, plasmid DNA analysis of Enterobacter sp. strain SVUB4 indicated the presence of a single large plasmid element. The results of plasmid curing experiments demonstrated that the ability of this strain to grow in presence of Cd and Zn was encoded by the 98 kb plasmid, whereas the ability to grow in the presence of Pb appeared to be encoded by the chromosome. The Cd and Zn removal capacity of the respective metal sensitive strain (plasmidless) were about 36 and 45 μg/g-1 DW, respectively, while the removal capacity of the both metal by metal resistant strain (p SVUB4) showed a significantly higher Cd and Zn removal capacity of 153 and 228 μg/g?1 DW, respectively. However, both strains exhibited a similar pattern of Pb accumulation. The present observation also showed that for wild-type strain SVUB4 (pSVUB4), the overall level of IAA production in the absence and in the presence of Cd2+ or Zn2+was approximately the same. Nevertheless, strain SVUB4M in this respect appeared to be more sensitive to heavy metals: a noticeable decrease in IAA production was observed under the effect of both metals, especially with Cd2+.  相似文献   

8.
SYNOPSIS. A new species of Acanthamoeba was isolated from a culture of an established line of human choriocarcinoma cells. The identification of this strain, originally called the Oak Ridge strain, and the establishment of a new species for it were based on morphologic, serologic, and immunochemical studies. In general, the structure of the trophozoite did not differ significantly from that of other species of Acanthamoeba, except that a body which more closely resembled a centriole than material described previously as centriolar satellites was observed in trophozoites examined with the electron microscope. The dimensions of the trophozoite were the smallest among the species of Acanthamoeba. The cyst was typical of the genus, but differed from those of other species by its smaller size and the presence of numerous ostioles. Studies of the Oak Ridge strain by immunofluorescence using antisera developed against the isolate and Acanthamoeba culbertsoni, A. castellanii, A. polyphaga, A. rhysodes, A. astronyxis, and A. palestinensis revealed the antigenic uniqueness of the Oak Ridge strain. It was demonstrated by immunoelectrophoretic analyses of the soluble proteins of the Oak Ridge strain that it shared ~ 1/2 of its antigenic structure with A. castellanii and A. culbertsoni. The antigenic differences of the isolate from other species of Acanthamoeba were deduced from comparison of the antigenic constitution of these species and the Oak Ridge strain with A. culbertsoni and A. castellanii. Although the strain was initially recognized by its cytopathogenicity for cultures, it did not produce acute infections in mice after intranasal inoculation of 1 × 104 amebae/mouse. The foregoing results constituted the basis for the establishment of the Oak Ridge strain as a new species, A. royreba sp. n., in the genus Acanthamoeba.  相似文献   

9.
Prototrophic bacteria grow on M-9 minimal salts medium supplemented with glucose (M-9 medium), which is used as a carbon and energy source. Auxotrophs can be generated using a transposome. The commercially available, Tn5-derived transposome used in this protocol consists of a linear segment of DNA containing an R6Kγ replication origin, a gene for kanamycin resistance and two mosaic sequence ends, which serve as transposase binding sites. The transposome, provided as a DNA/transposase protein complex, is introduced by electroporation into the prototrophic strain, Enterobacter sp. YSU, and randomly incorporates itself into this host’s genome. Transformants are replica plated onto Luria-Bertani agar plates containing kanamycin, (LB-kan) and onto M-9 medium agar plates containing kanamycin (M-9-kan). The transformants that grow on LB-kan plates but not on M-9-kan plates are considered to be auxotrophs. Purified genomic DNA from an auxotroph is partially digested, ligated and transformed into a pir+ Escherichia coli (E. coli) strain. The R6Kγ replication origin allows the plasmid to replicate in pir+ E. coli strains, and the kanamycin resistance marker allows for plasmid selection. Each transformant possesses a new plasmid containing the transposon flanked by the interrupted chromosomal region. Sanger sequencing and the Basic Local Alignment Search Tool (BLAST) suggest a putative identity of the interrupted gene. There are three advantages to using this transposome mutagenesis strategy. First, it does not rely on the expression of a transposase gene by the host. Second, the transposome is introduced into the target host by electroporation, rather than by conjugation or by transduction and therefore is more efficient. Third, the R6Kγ replication origin makes it easy to identify the mutated gene which is partially recovered in a recombinant plasmid. This technique can be used to investigate the genes involved in other characteristics of Enterobacter sp. YSU or of a wider variety of bacterial strains.  相似文献   

10.
Pyridine-2,6-dithiocarboxylic acid (pdtc) is a metal chelator produced by Pseudomonas spp. It has been shown to be involved in the biodegradation of carbon tetrachloride; however, little is known about its biological function. In this study, we examined the antimicrobial properties of pdtc and the mechanism of its antibiotic activity. The growth of Pseudomonas stutzeri strain KC, a pdtc-producing strain, was significantly enhanced by 32 μM pdtc. All nonpseudomonads and two strains of P. stutzeri were sensitive to 16 to 32 μM pdtc. In general, fluorescent pseudomonads were resistant to all concentrations tested. In competition experiments, strain KC demonstrated antagonism toward Escherichia coli. This effect was partially alleviated by 100 μM FeCl3. Less antagonism was observed in mutant derivatives of strain KC (CTN1 and KC657) which lack the ability to produce pdtc. A competitive advantage was restored to strain CTN1 by cosmid pT31, which restores pdtc production. pT31 also enhanced the pdtc resistance of all pdtc-sensitive strains, indicating that this plasmid contains elements responsible for resistance to pdtc. The antimicrobial effect of pdtc was reduced by the addition of Fe(III), Co(III), and Cu(II) and enhanced by Zn(II). Analyses by mass spectrometry determined that Cu(I):pdtc and Co(III):pdtc2 form immediately under our experimental conditions. Our results suggest that pdtc is an antagonist and that metal sequestration is the primary mechanism of its antimicrobial activity. It is also possible that Zn(II), if present, may play a role in pdtc toxicity.  相似文献   

11.
Anaerobic enrichments with acetate as the electron donor and Fe(III) as the terminal electron acceptor were obtained from sediments of Salt Pond, a coastal marine basin near Woods Hole, Mass. A pure culture of a facultatively anaerobic Fe(III) reducer was isolated, and 16S rRNA analysis demonstrated that this organism was most closely related to Pantoea (formerly Enterobacter) agglomerans, a member of the family Enterobacteriaceae within the gamma subdivision of the Proteobacteria. This organism, designated strain SP1, can grow by coupling the oxidation of acetate or H2 to the reduction of a variety of electron acceptors, including Fe(III), Mn(IV), Cr(VI), and the humic substance analog 2,6-anthraquinone disulfonate, but not sulfate. To our knowledge, this is the first mesophilic facultative anaerobe reported to couple acetate oxidation to dissimilatory metal reduction.  相似文献   

12.
《Genomics》2019,111(4):913-920
Enterobacter sp. J49 is a plant growth promoting endophytic strain that promotes the growth of peanut and maize crops. This strain promotes plant growth by different mechanisms with the supply of soluble phosphorus being one of the most important. Enterobacter sp. J49 not only increases the phosphorus content in the plant but also in the soil favoring the nutrition of other plants usually used in rotation with these crops. The aims of this study were to analyze the genome sequence of Enterobacter sp. J49 in order to deepen our knowledge regarding its plant growth promoting traits and to establish its phylogenetic relationship with other species of Enterobacter genus. Genome sequence of Enterobacter sp. J49 is a valuable source of information to continuing the research of its potential industrial production as a biofertilizer of peanut, maize and other economically important crops.  相似文献   

13.
The microbial degradation of 10 linear unsaturated dimers (I to IV) prepared from styrene and o-, m-, or p-methylstyrene was investigated with two soil bacteria, Alcaligenes sp. strain 559 and Pseudomonas sp. strain 419. The two strains decomposed styrene dimer I and all styrene-methylstyrene codimers II and III, but methylstyrene homodimers IV remained intact. The degradation rates of codimers II and III of o- and m-methylstyrenes were found to depend on both their structure and the strain used; i.e., Alcaligenes sp. strain 559 decomposed III faster than II, whereas the reverse order (II > III) was obtained with Pseudomonas sp. strain 419. In biodegradation by the former strain, the codimers were degraded faster in the presence of styrene dimer I than in its absence, but no such effect of dimer I was observed with the latter.  相似文献   

14.
Geobacter lovleyi strain SZ reduces hexavalent uranium, U(VI), to U(IV) and is the first member of the metal-reducing Geobacter group capable of using tetrachloroethene (PCE) as a growth-supporting electron acceptor. Direct and nested PCR with specific 16S rRNA gene-targeted primer pairs distinguished strain SZ from other known chlorinated ethene-dechlorinating bacteria and closely related Geobacter isolates, including its closest cultured relative, G. thiogenes. Detection limits for direct and nested PCR were approximately 1 × 106 and 1 × 104 16S rRNA gene copies per μl of template DNA, respectively. A quantitative real-time PCR (qPCR) approach increased the sensitivity to as few as 30 16S rRNA gene copies per μl of template DNA but was less specific. Melting curve analysis and comparison of the shapes of amplification plots identified false-positive signals and distinguished strain SZ from G. thiogenes when analyzed separately. These indicators were less reliable when target (strain SZ) DNA and nontarget (G. thiogenes) DNA with high sequence similarity were mixed, indicating that the development of qPCR protocols should not only evaluate specificity but also explore the effects of nontarget DNA on the accuracy of quantification. Application of specific tools detected strain SZ-like amplicons in PCE-dechlorinating consortia, including the bioaugmentation consortium KB-1, and two chlorinated ethene-impacted groundwater samples. Strain SZ-like amplicons were also detected in 13 of 22 groundwater samples following biostimulation at the uranium- and chlorinated solvent-contaminated Integrated Field-Scale Subsurface Research Challenge (IFC) site in Oak Ridge, TN. The numbers of strain SZ-like cells increased from below detection to 2.3 × 107 ± 0.1 × 107 per liter groundwater, suggesting that strain SZ-like organisms contribute to contaminant transformation. The G. lovleyi strain SZ-specific tools will be useful for monitoring bioremediation efforts at uranium- and/or chlorinated solvent-impacted sites such as the Oak Ridge IFC site.  相似文献   

15.
We report the discovery and validation of a set of single nucleotide polymorphisms (SNPs) between the reference Neurospora crassa strain Oak Ridge and the Mauriceville strain (FGSC 2555), of sufficient density to allow fine mapping of most loci. Sequencing of Mauriceville cDNAs and alignment to the completed genomic sequence of the Oak Ridge strain identified 19,087 putative SNPs. Of these, a subset was validated by cleaved amplified polymorphic sequence (CAPS), a simple and robust PCR-based assay that reliably distinguishes between SNP alleles. Experimental confirmation resulted in the development of 250 CAPS markers distributed evenly over the genome. To demonstrate the applicability of this map, we used bulked segregant analysis followed by interval mapping to locate the csp-1 mutation to a narrow region on LGI. Subsequently, we refined mapping resolution to 74 kbp by developing additional markers, resequenced the candidate gene, NCU02713.3, in the mutant background, and phenocopied the mutation by gene replacement in the WT strain. Together, these techniques demonstrate a generally applicable and straightforward approach for the isolation of novel genes from existing mutants. Data on both putative and validated SNPs are deposited in a customized public database at the Broad Institute, which encourages augmentation by community users.  相似文献   

16.
A mercury resistant strain of Enterobacter sp. is reported. The strain exhibited a novel property of mercury bioaccumulation with simultaneous synthesis of mercury nanoparticles. The culture conditions viz. pH 8.0 and lower concentration of mercury promotes synthesis of uniform sized 2-5 nm, spherical and monodispersed intracellular mercury nanoparticles. The remediated mercury trapped in the form of nanoparticles is unable to vaporize back into the environment thus, overcoming the major drawback of mercury remediation process. The mercury nanoparticles were recoverable. The nanoparticles have been characterized by high resolution transmission electron microscopy, energy dispersive X-ray analysis, powder X-ray diffraction and atomic force microscopy. The strain can be exploited for metal bioaccumulation from environmental effluent and developing a green process for nanoparticles biosynthesis.  相似文献   

17.
A unique cationic polyglucosamine biopolymer PGB-1 comprising more than 95% D-glucosamine was excretively produced from a new bacterial strain Enterobacter sp. BL-2 under acetate-mediated culture conditions. Since the biopolymer PGB-1 could be synthesized from the UDP-N-acetylglucosamine monomer derived from the hexosamine pathway, three glmS, glmM, and glmU genes in the hexosamine pathway were cloned from Enterobacter sp. BL-2, and their molecular structures were elucidated. The cloned glmS, glmM, and glmU genes were reintroduced into the parent strain Enterobacter sp. BL-2 through a conjugative transformation for the overproduction of the biopolymer PGB-1. The biopolymer production increased 1.5-fold in the transconjugant Enterobacter sp. BL-2S over-expressing the first-step glmS gene encoding glucosamine-6-phosphate synthase. The transconjugant Enterobacter sp. BL-2S was cultivated pH-stat fed-batch widely, while intermittently feeding an acetate solution to maintain a constant pH level of 8.0 for 72 h, resulting in 1.15 g/L of the extracellular polyglucosamine biopolymer PGB-1.  相似文献   

18.
Reaction of the potent hydroxamate-based histone deacetylase (HDAC) inhibitor, suberoylanilide hydroxamic acid (SAHA), with hydrated metal salts of Fe(III), Cu(II), Ni(II) and Zn(II) yielded a tris-hydroxamato complex in the case of Fe(III) and bis-hydroxamato complexes in the case of Cu(II), Ni(II) and Zn(II) both in the solid state and in solution. Reaction of the secondary hydroxamic acid, N-Me-SAHA, also yielded a tris-hydroxamato complex in the case of Fe(III) and bis-hydroxamato complexes in the case of Cu(II), Ni(II) and Zn(II) in solution. These metal complexes have the hydroxamato moiety coordinated in an O,O’-bidentate fashion. Stability constants of the metal complexes formed with SAHA and N-Me-SAHA in a DMSO/H2O 70/30%(v/v) mixture are described. A novel crystal structure of SAHA together with a novel synthesis for N-Me-SAHA are also reported.  相似文献   

19.
Larvae of the mayfly (Drunella grandis [Eaton]) from Diamond Fork Creek, Utah, were covered with a heavy growth of the sulfide-oxidizing bacterium Thiothrix. The bacterium did not seem to harm the mayfly, but the Thiothrix trichomes were parasitized by three morphologically distinct bacteria, two of which were cytoplasmic and one of which was probably periplasmic. At least two of the parasites destroyed the cytoplasmic contents of the Thiothrix sp., thus killing the host cell. Attempts to obtain the parasites in pure culture were unsuccessful.  相似文献   

20.
A new ethylenediaminetetraacetic acid (EDTA)-utilizing gammaproteobacterial strain LPM-5T was isolated from municipal sewage sludge. Aerobic, gram-negative, motile rods multiply by binary fission. Neutrophilic and mesophilic, these are unable to grow in the presence of 3% NaCl (w/v), and unable to reduce nitrate to nitrite, and are oxidase and catalase positive, but lipase negative. The major cellular fatty acids are Ci15:0, Ca15:0 and C16:1w7c. The dominant phospholipids are phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol (cardiolipin). The DNA G+C content is 68.3 mol% (Tm). The 16S rRNA gene sequence analysis showed a high similarity of strain LPM-5T to the species members of genus Stenotrophomonas: S. maltophilia LMG 958T (98.6%), S. rhizophila CCUG 47042T (98.3%), S. koreensis TR6-01T (97.6%) and S. acidaminiphila CIP 106456T (97.0%). Based on these results and modest DNA–DNA hybridization levels with S. maltophilia VKM B-591T (=LMG 958T) (51%) and S. rhizophila CCUG 47042T (52%), the isolate was classified as a novel species, Stenotrophomonas chelatiphaga sp. nov. (type strain LPM-5T=VKM B-2486=DSM-21508=CCUG 57178).  相似文献   

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