The plasmid-borne czc operon ensures for resistance to Cd2+, Zn2+ and Co2+ ions through a tricomponent export pathway and is associated to various conjugative plasmids of A. eutrophus strains isolated from metal-contaminated industrial areas. The czc region of pMOL30 was reassessed especially for the segments located upstream and downstream the structural genes czc CBA. In cultures grown with high concentrations of heavy metals, czc-mediated efflux of cations is followed by a process of metal bioprecipitation. These observations led to the development of bioreactors designed for the removal of heavy metals from polluted effluents.
Abstract. The Tarim river basin in China is a huge inland arid basin, which is expected to be highly vulnerable to climatic changes, given that most water resources originate from the upper mountainous headwater regions. This paper focuses on one of these headwaters: the Kaidu river subbasin. The climate change impact on the surface and ground water resources of that basin and more specifically on the hydrological extremes were studied by using both lumped and spatially distributed hydrological models, after simulation of the IPCC SRES greenhouse gas scenarios till the 2050s. The models include processes of snow and glacier melting. The climate change signals were extracted from the grid-based results of general circulation models (GCMs) and applied on the station-based, observed historical data using a perturbation approach. For precipitation, the time series perturbation involves both a wet-day frequency perturbation and a quantile perturbation to the wet-day rainfall intensities. For temperature and potential evapotranspiration, the climate change signals only involve quantile based changes. The perturbed series were input into the hydrological models and the impacts on the surface and ground water resources studied. The range of impact results (after considering 36 GCM runs) were summarized in high, mean, and low results. It was found that due to increasing precipitation in winter, snow accumulation increases in the upper mountainous areas. Due to temperature rise, snow melting rates increase and the snow melting periods are pushed forward in time.Correspondence to: P. Willems (patrick.willems@bwk.kuleuven.be) Although the qualitive impact results are highly consistent among the different GCM runs considered, the precise quantitative impact results varied significantly depending on the GCM run and the hydrological model.
Pyoverdin production by Pseudomonas aeruginosa strain 7NSK2 was induced by Zn(II) in the presence of iron. A mutant was isolated in which Zn(II) no longer induced pyoverdin production. The sss gene which was inactivated in this mutant was cloned and sequenced. Its protein sequence showed 50% identity to the XerC protein of Escherichia coli, which is a member of the lambda integrase family of site-specific recombinases. An open reading frame was found upstream of sss whose protein sequence showed strong identity to DapF, the diaminopimelate epimerase. In E. coli, xerC is part of a multicistronic unit that also contains dapF. The sss gene of P. aeruginosa could restore site-specific recombination at cer in an E. coli xerC mutant and the E. coli xerC gene could complement a genomic sss mutation in P. aeruginosa.
The hereditary goitre of Afrikander cattle is an autosomal recessive disease characterized in homozygotes by the production of abnormal thyroglobulin (Tg) and the coexistence in the thyroid of normal-sized 8.4-kilobase (kb) Tg mRNA with a misspliced 7.3-kb message having lost exon 9. We have cloned and sequenced the cDNA segment corresponding to the abnormal exon 8-exon 10 junction and the relevant genomic DNA region. The mutation responsible for the disease is a cytosine to thymine transition creating a stop codon at position 697 in exon 9. The original reading frame is maintained in the 7.3-kb mRNA, which, as it lacks the mutated exon, is translatable into a potentially functional protein. This puzzling phenotype in which a mutated exon is apparently removed selectively from transcripts by alternative splicing leads us to suggest that the 7.3-kb transcript could be present in normal animals. Using a sensitive oligonucleotide hybridization assay, we have demonstrated that a 7.3-kb mRNA lacking exon 9 does exist in normal thyroids as a minor mRNA species. As it is fully translatable, the 7.3-kb mRNA is expected to be more stable than the normal-sized 8.4-kb message. This probably accounts for the higher proportion of 7.3-kb transcript found in the goitre.Thyroglobulin (Tg), a 660-kDa homodimer, is the biosynthetic precursor of the thyroid hormones (1). The Tg gene is -250,000 nucleotide pairs long, ofwhich 8431 nucleotides are represented in the mRNA (2). Congenital goitres with defective Tg production have been described in humans (3) and in animal models (4, 5). They are usually associated with hypothyroidism and may lead, in humans, to the development of the "cretin" phenotype (6). The hereditary goitre of the Afrikander cattle is inherited as an autosomal recessive disease (7). The goitre ofhomozygotes contains no normal Tg (8) and contains both a shorter and a normal-sized Tg mRNA (9); exon 9 is absent in the shorter Tg mRNA, suggesting that a splicing error is responsible for the disease (9). To identify precisely the mutation, we have cloned and sequenced the cDNA of the affected region of the smaller mRNA and the exon 9-intron 9 region of the genomic DNA from both a normal individual and an individual with goitre. We show that a cytosine to thymine transition in exon 9, changing codon 697 from CGA (arginine) to TGA (stop) is responsible for the disease. The nonsense mutation in exon 9 is apparently associated with and partially cured by removal of the defective exon from a portion ofTg transcripts. An explanation for this curious phenotype was obtained by the identification of a minor mRNA species lacking exon 9 in the thyroids of normal animals. Different stability of the shorter (fully translatable) and larger (containing an early stop codon) messages probably accounts for their relative amounts in goitre tissue.
Screening 10(6) plaque-forming units from a lambda gt11 human thyroid cDNA library with a pool of 10 sera from patients with Hashimoto's thyroiditis resulted in the isolation of a clone, D1, of 292 basepairs with an open reading frame of 97 amino acids which did not share significant similarity with any known protein. Rescreening the library using D1 as a probe led to the full-length cDNA being cloned and sequenced which has the potential to encode a 572-amino acid polypeptide. This would correspond to a 63-kDa nonglycosylated protein which is probably membrane bound. The recombinant fusion protein from the original D1 clone was recognized in dot blot or Western blot assays by 4 of 19 patients with Hashimoto's thyroiditis, 3 of 9 patients with Graves' disease, and 1 of 6 patients with idiopathic myxedema; all other sera (12), including that from normal subjects, were negative. Clone affinity-purified autoantibodies bound to a protein of 64 kDa in a Western blot of human thyroid tissue. Using D1 as a probe in a Northern blot revealed 3.9-kilobase (kb) transcripts in poly(A)+ RNA from normal human thyroid and extraocular muscle, but not skeletal muscle. The dog equivalent of D1 cDNA was isolated by screening 10(6) plaque-forming units from a dog thyroid cDNA library using clone D1. A fragment of dog cDNA was, in turn, used as a probe in a Northern blot of dog poly(A)+ RNAs from thyroid, brain, lung, heart, liver, kidney, spleen, and stomach; a faint signal at 3.9 kb was observed in all tissues except the thyroid, which displayed a strong transcript of 2.6 kb. It is concluded that the D1 cDNA clone encodes an autoantigen shared by the thyroid and eye muscle. Its possible relevance to autoimmune ophthalmopathy is discussed.
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