The biochemical basis for resistance to metal ion toxicity is emerging though it is complicated by the different resistance mechanisms. Several strategies for resistance to toxic metal ions have been identified:
The development of energy driven efflux pumps which keep toxic element levels low in the interior of the cell. Such mechanisms have been described for Cd(II) and As(V).
Oxidation (e.g. AsO2‐ to AsO43‐) or reduction (e.g. Hg2+ to Hg0) can enzymatically and intracellularly convert a more toxic form of an element to a less toxic form.
The biosynthesis of intracellular polymers which serve as traps for the removal of metal ions from solution such as traps have been described for cadmium, calcium, nickel and copper.
The binding of metal ions to cell surfaces.
The precipitation of insoluble metal complexes (e.g. metal sulfides and metal oxides) at cell surfaces.
Biomethylation and transport through cell‐membranes by diffusion controlled processes.
In this short review I shall discuss the implications of biomethylation as a detoxification mechanism for microorganisms as well as for certain higher organisms. 相似文献
Quantitative determination of dimethylselenide and dimethyldiselenide in the breath of mice after addition of different selenium compounds to the drinking water is described. Breath samples are collected with a cryogenic trap and analyzed by gas chromatography with atomic absorption spectrometric detection. Detection limits down to 0.2 ng/100 g body weight are obtained. The pulmonary excretion of selenium metabolites after oral administration via drinking water or after intraperitoneal injection appears to be negligible. The bioconversion of the different selenium species is discussed. 相似文献
The degradation kinetic parameters in terephthalic acid (TPA) wastewater for the hybrid strains of Fhh and Fhhh obtained through the protoplast fusion of the fungi Phanerochaete chrysosporium (PC) and Saccharomyces cerevisiae Y99, and the native bacteria YZ1 were measured in this research. The highest level of the specific degradation rate for Fhhh and Fhh during 20h reaction were 0.2238 and 0.2163 h‐1, which were higher than that of their three parental strains and that of the anaerobic bacteria reported. It suggested that the abilities of growth and degradation for Fhh and Fhhh in TPA wastewater were better than their three parental strains. They could create potentials for the purification of TPA wastewater with higher efficiency. 相似文献
New oxovanadium(IV) mixed-ligand complexes of the general composition [VO(L)(A)], where KHL?=?potassium salt of salicylideneglycine, A1?=?bis(benzylidene)ethylenediamine, A2?=?bis (acetophenone)ethylenediamine, A3?=?di(2-pyridyl)amine, A4?=?bis(benzylidene)-1,8-diaminonaphthalene, A5?=?thiophene-o-carboxaldene-aniline, A6?=?thiophene-o-carboxaldene-p-anisidine, have been synthesized by the interaction of these ligands with vanadyl sulphate. The mixed-ligand complexes have been characterized on the basis of elemental analysis, magnetic measurements, electronic and infrared spectra. An octahedral structure has tentatively been assigned to all of the mixed-ligand complexes. The mixed-ligand complexes show higher toxic activity against the Salmonella typhi, Escherichia coli and Serratia mercescen as compared to the ligands, vanadyl sulphate and control (dimethyl sulphoxide). The mixed-ligand complexes were also tested against a standard drug (tetracycline). 相似文献
ABSTRACTAlthough sustainable development was defined in the Brundtland Report almost 30 years ago, the current usage of the concepts of sustainability and sustainable development remain highly equivocal. In the context of rural communities, multiple interpretations and weak definitions lead to confusion in understanding what comprises a sustainable rural community. Building on existing definitions (e.g. Baker’s, 2006, ‘Ladder of Sustainable Development’), models (principally, The Egan Review’s, 2004, ‘Components of Sustainable Communities’) and findings of this study, a sustainable community is defined and a holistic model of a sustainable place-based rural community is presented. This model, the sustainable community design (SCD) is used as the basis for analysing community sustainability, which is measured using mixed methods and scorecard assessment. Sensitivity of the method is demonstrated with inter- and intra-community variations in sustainability across three diverse Scottish rural communities. Intra-community variations illustrate heterogeneity in community sustainability, explain ambiguity in characterisations of an individual community’s sustainability, and highlight the importance of an interdisciplinary and holistic approach to community development. The SCD framework is presented as a useful tool for meso-level sustainability assessment and to facilitate the sustainable development of rural communities. 相似文献