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At least 1,801 records · Page 100Linked to original sources
PubMed1994

Mercury toxicokinetics in Wistar rats exposed to elemental mercury vapour: modeling and computer simulation.

The kinetics of total mercury (Hg) absorption, distribution and elimination in Wistar rats exposed for long periods to elemental mercury vapour (Hg zero) in the Idrija mercury mine were studied. From the experimental data base a compartmental model was built as a framework for experimental data interpretation and prediction of organ mercury levels under different conditions. Using the model the exposures of rats under conditions comparable to those of professionally exposed workers (mercury miners, workers in the chloralkali industry) and individuals with amalgam fillings were simulated.

Animals↗
PubMed2004

Sulfate-reducing bacteria-dominated biofilms that precipitate ZnS in a subsurface circumneutral-pH mine drainage system.

The microbial diversity of ZnS-forming biofilms in 8 degrees C, circumneutral-pH groundwater in tunnels within the abandoned Piquette Zn, Pb mine (Tennyson, Wisconsin, USA) has been investigated by molecular methods, fluorescence in situ hybridization (FISH), and cultivation techniques. These biofilms are growing on old mine timbers that generate locally anaerobic zones within the mine drainage system. Sulfate-reducing bacteria (SRB) exclusively of the family Desulfobacteriaceae comprise a significant fraction of the active microbiota. Desulfosporosinus strains were isolated, but could not be detected by molecular methods. Other important microbial clusters belonged to the beta-, gamma-, and epsilon-Proteobacteria, the Cytophaga/Flexibacter/Bacteroides-group (CFB), Planctomycetales, Spirochaetales, Clostridia, and green nonsulfur bacteria. Our investigations indicated a growth dependence of SRB on fermentative, cellulolytic, and organic acid-producing Clostridia. A few clones related to sulfur-oxidizing bacteria were detected, suggesting a sulfur cycle related to redox gradients within the biofilm. Sulfur oxidation prevents sulfide accumulation that would lead to precipitation of other sulfide phases. FISH analyses indicated that Desulfobacteriaceae populations were not early colonizers in freshly grown and ZnS-poor biofilms, whereas they were abundant in older, naturally established, and ZnS-rich biofilms. Gram-negative SRB have been detected in situ over a period of 6 months, supporting the important role of these organisms in selective ZnS precipitation in Tennyson mine. Results demonstrate the complex nature of biofilms responsible for in situ bioremediation of toxic metals in a subsurface mine drainage system.

Bacteria↗
PubMed2005

Complete mineralisation of dimethylformamide by Ochrobactrum sp. DGVK1 isolated from the soil samples collected from the coalmine leftovers.

A bacterial strain DGVK1 capable of using N,N-dimethylformamide (DMF) as sole source of carbon and nitrogen was isolated from the soil samples collected from the coalmine leftovers. The molecular phylogram generated using the complete sequence of 16S rDNA of the strain DGVK1 showed close links to the bacteria grouped under Brucellaceae family that belongs to alphaproteobacteria class. Specifically, the 16S rDNA sequence of strain DGVK1 has shown 97% similarity to Ochrobactrum anthropi LMG 3331 (D12794). This bacterium has also shown impressive growth on dimethylamine, methylamine, formaldehyde and formate that are considered to be the prominent catabolic intermediates of DMF. DMF degradation has led to the accumulation of ammonia and dimethylamine contributing to the increase of pH of the medium. The DMF-grown resting cells of Ochrobactrum sp. DGVK1 have also contributed for the release of ammonia when resting cell suspension was added to phosphate buffer containing DMF. Similar experiments done with the glucose-grown cultures have not produced ammonia and thus indicating the inducible nature of DMF-degrading enzymes in Ochrobactrum sp. DGVK1. Further, dimethylformamidase, dimethylamine dehydrogenase and methylamine dehydrogenase, the key enzymes involved in the degradation of DMF, were assayed, and the activities of these enzymes were found only in DMF-grown cultures further confirming the inducible nature of the DMF degradation. Based on these results, DMF degradation pathway found in Ochrobactrum sp. DGVK1 has been proposed.

Biodegradation, Environmental↗
PubMed2002

Resistance to cadmium and zinc in Acidiphilium symbioticum KM2 is plasmid mediated.

The acidophilic heterotroph, Acidiphilium symbioticum KM2, is highly resistant to several metals and harbors three plasmids of 3.8, 7.1, and 56 kb in size. The bacterium becomes extremely sensitive to metals when it is cured of its plasmids. A mini-plasmid library was constructed by ligating the plasmid DNA fragments generated by MboI partial digestion into the BamHI site of pBluescriptII KS+. The Lac(-)Amp(r) transformants of Escherichia coli DH5alpha, isolated after transformation with the library, were counter-selected on Cu(2+), Cd(2+), Ni(2+), and Zn(2+)-containing plates. Only Cd(2+)- and Zn(2+)-resistant colonies were developed, and, after screening, four types of recombinant plasmids designated as pNM201 (7.2 kb), pNM206 (3.4 kb), pNM208 (4.5 kb), and pNM215 (4.9 kb) were obtained. The DNA insert in pNM206 hybridized strongly with the 3.8-kb plasmid and weakly with the 7.1-kb plasmid of Acidiphilium symbioticum KM2. The DNA insert in pNM215 hybridized only with the 7.1-kb plasmid. These results strongly suggested that resistance to cadmium and zinc in A. symbioticum KM2 is mediated by these plasmids. The smallest insert of 422 bp in pNM206 conferring metal resistance in E. coli has no sequence similarity with the reported metal-resistant genes. All the putative ORFs are significantly rich (up to 37%) in basic amino acids, mainly arginine.

Acetobacteraceae↗
PubMed2006

Phylogenetic analysis of bacterial isolates from man-made high-pH, high-salt environments and identification of gene-cassette-associated open reading frames.

Environmental samples were collected from high-pH sites in Pakistan, including a uranium heap set up for carbonate leaching, the lime unit of a tannery, and the Khewra salt mine. Another sample was collected from a hot spring on the shore of the soda lake, Magadi, in Kenya. Microbial cultures were enriched from Pakistani samples. Phylogenetic analysis of isolates was carried out by sequencing 16S rRNA genes. Genomic DNA was amplified by polymerase chain reaction using integron gene-cassette-specific primers. Different gene-cassette-linked genes were recovered from the cultured strains related to Halomonas magadiensis, Virgibacillus halodenitrificans, and Yania flava and from the uncultured environmental DNA sample. The usefulness of this technique as a tool for gene mining is indicated.

Alkalies↗
PubMed2004

Characterization of iron- and sulphide mineral-oxidizing moderately thermophilic acidophilic bacteria from an Indonesian auto-heating copper mine waste heap and a deep South African gold mine.

Iron- and chalcopyrite-oxidizing enrichment cultures were obtained at 50 degrees C from acidic, high-temperature, copper/gold mine environments in Indonesia and South Africa. Over 90% copper yield was obtained from chalcopyrite concentrate with the Indonesian enrichment in 3 months with 2% solids concentration, when pH was maintained at around 2. Neither addition of silver cations nor an enhanced nutrient concentration influenced chalcopyrite leaching. Excision and sequencing of bands from denaturing gradient gel electrophoresis of the amplified partial 16S rRNA gene showed that the enrichment cultures from different environments in South Africa and Indonesia were very simple, and similar. Chalcopyrite concentrate supported a simpler and different community than Fe2+. The members of the enrichment cultures were closely related to Sulfobacillus yellowstonensis and Sulfobacillus acidophilus.

Bacteria↗
PubMed1992

Mutations of p53 and ras genes in radon-associated lung cancer from uranium miners.

Radon increases the risk of lung cancer in smoking and non-smoking underground miners. To investigate the mutational spectrum associated with exposure to high levels of radon, we sequenced exons 5-9 of the p53 tumour suppressor gene and codons 12-13 of the Ki-ras protooncogene in 19 lung cancers from uranium miners exposed to radon and tobacco smoke. Mutations were not found in Ki-ras, but 9 p53 mutations, including 2 deletions, were found in 7 patients by direct DNA sequencing after polymerase chain reaction amplification of DNA from formalin-fixed, paraffin-embedded tissue. In tumours from 5 patients, the mutation produced an aminoacid change and an increased nuclear content of p53 protein. The tumours with either a stop codon or frame-shift deletion in the p53 gene were negative by immunohistochemistry. None of the mutations were G:C to T:A transversions in the coding strand of the p53 gene, which are the most frequent base substitutions associated with tobacco smoking, and none were found at the hotspot codons described in lung cancer. The observed differences from the usual lung cancer mutational spectrum may reflect the genotoxic effects of radon.

Aged↗
PubMed2005

Genetic diversity of merozoite surface protein-1 gene of Plasmodium vivax isolates in mining villages of Venezuela (Bolivar State).

The merozoite surface protein-1 gene of Plasmodium vivax is highly polymorphic and so, currently used in epidemiological studies of P. vivax malaria. We sequenced the variable block 5 of the gene from 39 Venezuelan isolates, 18 of which were co-infected with Plasmodium falciparum. We observed a limited variability with 34 isolates belonging to the type Salvador I, none Belem type and only five recombinants. Among the recombinants, only two types of sequences were observed with, respectively, 18 and 21 poly-Q residues. Nucleotide substitutions explained the major differences of the 11 patterns observed. We could evidence neither specific MSP-1 genotype associated with co-infected samples, nor peculiar MSP-1 genotype distribution inside the investigated areas. In comparison with other low endemic regions in the world, our sampling has a lower genetic diversity, which could be mainly explained by the lack of Belem type. In fact, the variable repeats of poly-Q residues involved in the polymorphism of Belem type and recombinant isolates are responsible for a great part of variability observed in MSP-1 block 5.

Adult↗
PubMed2005

Plasmodium falciparum: IgG subclass antibody response to merozoite surface protein-1 among Amazonian gold miners, in relation to infection status and disease expression.

The merozoite surface protein-1 (MSP-1) of Plasmodium falciparum comprises two major targets of antibody-mediated immunity: the polymorphic block 2 and the 19-kDa C-terminal domain MSP-1(19). Here, we measured antibodies to three block 2 variants and MSP-1(19) among Amazonian gold miners and examined the repertoire of block 2 variants in local parasites. Main findings were as follows: (1) Only seven different block 2 variants were found in 18 DNA sequences analyzed. (2) No major difference was observed in IgG subclass distribution of antibodies from symptomatic P. falciparum-infected patients, asymptomatic parasite carriers, and non-infected subjects. (3) Antibodies to all block 2 antigens, but not to MSP-1(19), were biased towards IgG3 across different strata of cumulative malaria exposure. (4) Similar proportions of symptomatic and asymptomatic subjects failed to recognize the block 2 variant expressed by infecting parasites. These negative results underscore the limits of conventional antibody assays to evaluate clinical immunity to malaria.

Adolescent↗
PubMed2004

Effect of carbon and nitrogen input on the bacterial community structure of Neocaledonian nickel mine spoils.

Neocaledonian mine spoils are considered as an extreme environment because of their edaphic conditions, which are unfavourable for life. The principal characteristics of this soil are the high nickel content (20,000 ppm) and the very low carbon (0.2%) and nitrogen (0.01%) levels, which are certainly among the major limiting factors for heterotrophic bacterial growth. The aim of this work was to determine what changes could occur in the bacterial community structure of the mine spoils when a carbon and a nitrogen source were added. Soil bacterial response to nutrient addition was examined in both the mine spoils and an agricultural soil, which is characterized by normal levels of nutrients. 16S rRNA gene clone libraries constructed to characterize changes occurring in the different soil bacterial communities showed an important selection of Actinobacteria in the mine spoils as a consequence of nutrient amendment: Actinobacteria represented 75% and 96% of the bacterial community structure after succinate and glucose addition, respectively. This was observed only in the mine spoils and is probably a consequence of the extreme environmental conditions. Carbon amendment in the agricultural soil led to an increase in Firmicutes, mainly Bacillus sp.

Actinobacteria↗
PubMed2004

Macrofilamentous microbial communities in the metal-rich and acidic River Tinto, Spain.

A novel type of macroscopic microbial community consisting of large dendritic filaments (up to 1.5 m) in a pH 2.0 dam of the River Tinto (South-western Spain) is described. The combined use of 16S rRNA-gene surveys and fluorescent in situ hybridisation (FISH) suggested that gamma-proteobacteria and a relative large diversity of alpha-proteobacteria dominated these structures. beta-Proteobacteria, Actinobacteria and Firmicutes were also detected. Whereas acidophilic bacteria of the genera Acidithiobacillus, Leptospirillum and Acidiphilium, and archaea belonging to the Thermoplasmatales dominate mine acid drainage waters and streamers (riverbed filamentous biofilms), none of the lineages identified in this study affiliate to typical acid mine drainage acidophilic bacteria. Bacteria of the Tinto macrofilaments might be heterotrophic, and could be feeding on the organic matter entrapped in the filamentous structure.

Actinobacteria↗
PubMed2005

Characterization of microorganisms isolated from lignite excavated from the Záhorie coal mine (southwestern Slovakia).

Microorganisms were isolated from lignite freshly excavated in the Záhorie coal mine (southwestern Slovakia) under conditions excluding contamination with either soil or air-borne microorganisms. The isolates represented both Prokarya and Eukarya (fungi). All were able to grow on standard media, although some microorganisms were unstable and became extinct during storage of coal samples. Bacteria belonged to the genera Bacillus, Staphylococcus, and Rhodococcus, according to both morphological criteria and ITS sequences. Several bacterial isolates were resistant to antibiotics. The presence of anaerobic bacteria was also documented, although they have not yet been identified. Fungal isolates were typified by using their ITS sequences. They belonged to the genera Trichoderma (Hypocrea), Penicillium, Epicoccum, Metarhizium (Cordyceps), and Cladosporium. Several fungi produced compounds with antibiotic action against standard bacterial strains. The evidence for the presence of microorganisms in native lignite was obtained by means of fluorescence microscopy, scanning electron microscopy, and electron microprobe analysis. Results demonstrated that microorganisms were able to survive in the low-rank coal over a long time period.

Anti-Bacterial Agents↗
PubMed2006

Arsenicicoccus bolidensis a novel arsenic reducing actinomycete in contaminated sediments near the Adak mine (northern Sweden): impact on water chemistry.

Weathering of mine tailings in Adak results in high As concentrations in surface and ground water, sediments, and soil. In spite of the oxic conditions, As-rich surface and ground water samples indicate As(III) species predominantly (up to 83%). Several microorganisms were isolated from the enrichment cultures that were involved in As cycling. Amongst them was Arsenicicoccus bolidensis - a novel gram-positive, facultatively anaerobic, coccus-shaped actinomycete, which actively reduced As(V) to As(III) in aqueous media. A. bolidensis reduced 0.06-0.20 mM day(-1) As(V). As(V) reduction displays a direct correlation between the initial As(V) concentration, growth rate, and biomass yield.

Actinomycetales↗
PubMed2006

Isolation and characterization of a Geobacillus thermoleovorans strain from an ultra-deep South African gold mine.

A thermophilic facultative bacterial isolate was recovered from 3.2km depth in a gold mine in South Africa. This isolate, designated GE-7, was cultivated from pH 8.0, 50 degrees C water from a dripping fracture near the top of an exploration tunnel. GE-7 grows optimally at 65 degrees C and pH 6.5 on a wide range of carbon substrates including cellobiose, hydrocarbons and lactate. In addition to O(2), GE-7 also utilizes nitrate as an electron acceptor. GE-7 is a long rod-shaped bacterium (4-6microm longx0.5microm wide) with terminal endospores and flagella. Phylogenetic analysis of GE-7 16S rDNA sequence revealed high sequence similarity with G. thermoleovorans DSM 5366(T) (99.6%), however, certain phenotypic characteristics of GE-7 were distinct from this and other previously described strains of G. thermoleovorans.

Bacillaceae↗
PubMed2005

Transcription control reprogramming in genetic backup circuits.

A key question in molecular genetics is why severe mutations often do not result in a detectably abnormal phenotype. This robustness was partially ascribed to redundant paralogs that may provide backup for one another in case of mutation. Mining mutant viability and mRNA expression data in Saccharomyces cerevisiae, we found that backup was provided predominantly by paralogs that are expressed dissimilarly in most growth conditions. We considered that this apparent inconsistency might be resolved by a transcriptional reprogramming mechanism that allows the intact paralog to rescue the organism upon mutation of its counterpart. We found that in wild-type cells, partial coregulation across growth conditions predicted the ability of paralogs to alter their transcription patterns and to provide backup for one another. Notably, the sets of regulatory motifs that controlled the paralogs with the most efficient backup activity deliberately overlapped only partially; paralogs with highly similar or dissimilar sets of motifs had suboptimal backup activity. Such an arrangement of partially shared regulatory motifs reconciles the differential expression of paralogs with their ability to back each other up.

Kinetics↗
PubMed2002

An arsenic(III)-oxidizing bacterial population: selection, characterization, and performance in reactors.

AIMS: To select an autotrophic arsenic(III)-oxidizing population, named CASO1, and to evaluate the performance of the selected bacteria in reactors. METHODS AND RESULTS: An As(III)-containing medium without organic substrate was used to select CASO1 from a mining environment. As(III) oxidation was studied under batch and continuous conditions. The main organisms present in CASO1 were identified with molecular biology tools. CASO1 exhibited significant As(III)-oxidizing activity between pH 3 and 8. The optimum temperature was 25 degrees C. As(III) oxidation was still observed in the presence of 1000 mg l(-1) As(III). In continuous culture mode, the As(III) oxidation rate reached 160 mg l(-1) h(-1). The CASO1 consortium contains at least two organisms - strain b3, which is phylogenetically close to Ralstonia picketii, and strain b6, which is related to the genus Thiomonas. The divergence in 16S rDNA sequences between b6 and the closest related organism was 5.9%, suggesting that b6 may be a new species. CONCLUSIONS: High As(III)-oxidizing activity can be obtained without organic nutrient supply, using a bacterial population from a mining environment. SIGNIFICANCE AND IMPACT OF THE STUDY: The biological oxidation of arsenite by the CASO1 population is of particular interest for decontamination of arsenic-contaminated waste or groundwater.

Arsenic↗
PubMed2001

Isolation and phylogenetic characterization of acidophilic microorganisms indigenous to acidic drainage waters at an abandoned Norwegian copper mine.

The biodiversity of culturable acidophilic microbes in three acidic (pH 2.7-3.7), metal-rich waters at an abandoned subarctic copper mine in central Norway was assessed. Acidophilic bacteria were isolated by plating on selective solid media, and dominant isolates were identified from their physiological characteristics and 16S rRNA gene sequences. The dominant iron-oxidizing acidophile in all three waters was an Acidithiobacillus ferrooxidans-like eubacterium, which shared 98% 16S rDNA identity with the type strain. A strain of Leptospirillum ferrooxidans was obtained from one of the waters after enrichment in pyrite medium, but this iron oxidizer was below detectable levels in the acidic waters themselves. In two sites, there were up to six distinct heterotrophic acidophiles, present at 10(3) ml(-1). These included Acidiphilium-like isolates (one closely related to Acidiphilium rubrum, a second to Acidiphilium cryptum and a third apparently novel isolate), an Acidocella-like isolate (96% 16S rDNA identity to Acidocella facilis) and a bacterium that shared 94.5% 16S rDNA identity to Acidisphaera rubrifaciens. The other numerically significant heterotrophic isolate was not apparently related to any known acidophile, with the closest match (96% 16S rDNA sequence identity) to an acetogen, Frateuria aurantia. The results indicated that the biodiversity of acidophilic bacteria, especially heterotrophs, in acidic mine waters may be much greater than previously recognized.

Copper↗
PubMed2003

Indigenous and contaminant microbes in ultradeep mines.

Rock, air and service water samples were collected for microbial analyses from 3.2 kilometres depth in a working Au mine in the Witwatersrand basin, South Africa. The approximately metre-wide mined zone was comprised of a carbonaceous, quartz, sulphide, uraninite and Au bearing layer, called the Carbon Leader, sandwiched by quartzite and conglomerate. The microbial community in the service water was dominated by mesophilic aerobic and anaerobic, alpha-, beta- and gamma-Proteobacteria with a total biomass concentration approximately 10(4) cells ml(-1), whereas, that of the mine air was dominated by members of the Chlorobi and Bacteroidetes groups and a fungal component. The microorganisms in the Carbon Leader were predominantly mesophilic, aerobic heterotrophic, nitrate reducing and methylotrophic, beta- and gamma-Proteobacteria that were more closely related to service water microorganisms than to air microbes. Rhodamine WT dye and fluorescent microspheres employed as contaminant tracers, however, indicated that service water contamination of most of the rock samples was < 0.01% during acquisition. The microbial contaminants most likely originated from the service water, infiltrated the low permeability rock through and accumulated within mining-induced fractures where they survived for several days before being mined. Combined PLFA and terminal restriction fragment length profile (T-RFLP) analyses suggest that the maximum concentration of indigenous microorganisms in the Carbon Leader was < 10(2) cells g(-1). PLFA, 35S autoradiography and enrichments suggest that the adjacent quartzite was less contaminated and contained approximately 10(3) cells gram(-1) of thermophilic, sulphate reducing bacteria, SRB, some of which are delta-Proteobacteria. Pore water and rock geochemical analyses suggest that these SRB's may have been sustained by sulphate diffusing from the adjacent U-rich, Carbon Leader where it was formed by radiolysis of sulphide.

Air Microbiology↗

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