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Metal Resistance (metal + resistance)
Selected AbstractsAdvances in Research on Genetically Engineered Plants for Metal ResistanceJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 11 2006Ri-Qing Zhang Abstract The engineering application of natural hyperaccumulators in removing or inactivating metal pollutants from soil and surface water in field trials mostly presents the insurmountable shortcoming of low efficiency owing to their little biomass and slow growth. Based on further understanding of the molecular mechanism of metal uptake, translocation, and also the separation, identification, and cloning of some related functional genes, this article highlights and summarizes in detail the advances in research on transgenic techniques, such as Agrobacterium tumefaciens -mediated transformation and particle bombardment, in breeding of plants for metal resistance and accumulation, and points out that deepening the development of transgenic plants is one of the efficient approaches to improving phytoremediation efficiency of metal-contaminated environments. From the viewpoint of sustainable development, governments should strengthen support to the development of genetic engineering for metal resistance and accumulation in plants. (Managing editor: Li-Hui Zhao) [source] GeoChip-based analysis of functional microbial communities during the reoxidation of a bioreduced uranium-contaminated aquiferENVIRONMENTAL MICROBIOLOGY, Issue 10 2009Joy D. Van Nostrand Summary A pilot-scale system was established for in situ biostimulation of U(VI) reduction by ethanol addition at the US Department of Energy's (DOE's) Field Research Center (Oak Ridge, TN). After achieving U(VI) reduction, stability of the bioreduced U(IV) was evaluated under conditions of (i) resting (no ethanol injection), (ii) reoxidation by introducing dissolved oxygen (DO), and (iii) reinjection of ethanol. GeoChip, a functional gene array with probes for N, S and C cycling, metal resistance and contaminant degradation genes, was used for monitoring groundwater microbial communities. High diversity of all major functional groups was observed during all experimental phases. The microbial community was extremely responsive to ethanol, showing a substantial change in community structure with increased gene number and diversity after ethanol injections resumed. While gene numbers showed considerable variations, the relative abundance (i.e. percentage of each gene category) of most gene groups changed little. During the reoxidation period, U(VI) increased, suggesting reoxidation of reduced U(IV). However, when introduction of DO was stopped, U(VI) reduction resumed and returned to pre-reoxidation levels. These findings suggest that the community in this system can be stimulated and that the ability to reduce U(VI) can be maintained by the addition of electron donors. This biostimulation approach may potentially offer an effective means for the bioremediation of U(VI)-contaminated sites. [source] The SmtB/ArsR family of metalloregulatory transcriptional repressors: structural insights into prokaryotic metal resistanceFEMS MICROBIOLOGY REVIEWS, Issue 2-3 2003Laura S. Busenlehner Abstract The SmtB/ArsR family of prokaryotic metalloregulatory transcriptional repressors represses the expression of operons linked to stress-inducing concentrations of di- and multivalent heavy metal ions. Derepression results from direct binding of metal ions by these homodimeric ,metal sensor' proteins. An evolutionary analysis, coupled with comparative structural and spectroscopic studies of six SmtB/ArsR family members, suggests a unifying ,theme and variations' model, in which individual members have evolved distinct metal selectivity profiles by alteration of one or both of two structurally distinct metal coordination sites. These two metal sites are designated ,3N (or ,3) and ,5 (or ,5C), named for the location of the metal binding ligands within the known or predicted secondary structure of individual family members. The ,3N/,3 sensors, represented by Staphylococcus aureus pI258 CadC, Listeria monocytogenes CadC and Escherichia coli ArsR, form cysteine thiolate-rich coordination complexes (S3 or S4) with thiophilic heavy metal pollutants including Cd(II), Pb(II), Bi(III) and As(III) via inter-subunit coordination by ligands derived from the ,3 helix and the N-terminal ,arm' (CadCs) or from the ,3 helix only (ArsRs). The ,5/,5C sensors Synechococcus SmtB, Synechocystis ZiaR, S. aureus CzrA, and Mycobacterium tuberculosis NmtR form metal complexes with biologically required metal ions Zn(II), Co(II) and Ni(II) characterized by four or more coordination bonds to a mixture of histidine and carboxylate ligands derived from the C-terminal ,5 helices on opposite subunits. Direct binding of metal ions to either the ,3N or ,5 sites leads to strong, negative allosteric regulation of repressor operator/promoter binding affinity, consistent with a simple model for derepression. We hypothesize that distinct allosteric pathways for metal sensing have co-evolved with metal specificities of distinct ,3N and ,5 coordination complexes. [source] Rapid evolution towards heavy metal resistance by mountain birch around two subarctic copper,nickel smeltersJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2008J. K. ERÄNEN Abstract Adaptations to pollution among long-lived trees have rarely been documented, possibly because of their long reproductive cycles and the evolutionarily short timescales of anthropogenic pollution. Here, I present the results of a greenhouse experiment that suggest rapid evolutionary adaptation of mountain birch [Betula pubescens subsp. czerepanovii (Orlova) Hämet-Ahti] to heavy metal (HM) stress around two copper,nickel smelters in NW Russia. The adaptation incurs a cost with reduced performance of adapted seedlings in pristine conditions. The industrial barrens around the studied smelters are extremely high-stress sites with low seed germination and survival. It is likely that strong natural selection has eliminated all sensitive genotypes within one or two generations, with only the most tolerant individuals persisting and producing adapted seeds in the individual barrens. The results were similar from around both smelters, suggesting parallel evolution towards HM resistance. [source] Advances in Research on Genetically Engineered Plants for Metal ResistanceJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 11 2006Ri-Qing Zhang Abstract The engineering application of natural hyperaccumulators in removing or inactivating metal pollutants from soil and surface water in field trials mostly presents the insurmountable shortcoming of low efficiency owing to their little biomass and slow growth. Based on further understanding of the molecular mechanism of metal uptake, translocation, and also the separation, identification, and cloning of some related functional genes, this article highlights and summarizes in detail the advances in research on transgenic techniques, such as Agrobacterium tumefaciens -mediated transformation and particle bombardment, in breeding of plants for metal resistance and accumulation, and points out that deepening the development of transgenic plants is one of the efficient approaches to improving phytoremediation efficiency of metal-contaminated environments. From the viewpoint of sustainable development, governments should strengthen support to the development of genetic engineering for metal resistance and accumulation in plants. (Managing editor: Li-Hui Zhao) [source] PRODUCTION OF PHYTOCHELATINS AND GLUTATHIONE BY MARINE PHYTOPLANKTON IN RESPONSE TO METAL STRESS,JOURNAL OF PHYCOLOGY, Issue 5 2006Silvia K. Kawakami Phytoplankton deal with metal toxicity using a variety of biochemical strategies. One of the strategies involves glutathione (GSH) and phytochelatins (PCs), which are metal-binding thiol peptides produced by eukaryotes and these compounds have been related to several intracellular functions, including metal detoxification, homeostasis, metal resistance and protection against oxidative stress. This paper assesses our state of knowledge on the production of PCs and GSH by marine phytoplankton in laboratory and field conditions and the possible applications of PCs for environmental purposes. Good relationships have been observed between metal exposure and PC production in phytoplankton in the laboratory with Cd, Pb, and Zn showing the greatest efficacy, thereby indicating that PCs have a potential for application as a biomarker. Fewer studies on PC distributions in particulate material have been undertaken in the field. These studies show that free Cu has a strong relationship with the levels of PC in the particulate material. The reason for this could be because Cu is a common contaminant in coastal waters. However it could also be due to the lack of measurements of other metals and their speciation. GSH shows a more complex relationship to metal levels both in the laboratory and in the field. This is most likely due to its multifunctionality. However, there is evidence that phytoplankton act as an important source of dissolved GSH in marine waters, which may form part of the strong organic ligands that control metal speciation, and hence metal toxicity. [source] | ||||||||||