RESUMO
Chromium is a highly toxic non-essential metal for microorganisms and plants. Due to its widespread industrial use, chromium (Cr) has become a serious pollutant in diverse environmental settings. The hexavalent form of the metal, Cr(VI), is considered a more toxic species than the relatively innocuous and less mobile Cr(III) form. The presence of Cr in the environment has selected microbial and plant variants able to tolerate high levels of Cr compounds. The diverse Cr-resistance mechanisms displayed by microorganisms, and probably by plants, include biosorption, diminished accumulation, precipitation, reduction of Cr(VI) to Cr(III), and chromate efflux. Some of these systems have been proposed as potential biotechnological tools for the bioremediation of Cr pollution. In this review we summarize the interactions of bacteria, algae, fungi and plants with Cr and its compounds.
Assuntos
Cromo/farmacologia , Poluentes Ambientais/toxicidade , Sequência de Aminoácidos , Bactérias/efeitos dos fármacos , Biodegradação Ambiental , Cromo/análise , Cromo/química , Cromo/farmacocinética , Cromo/toxicidade , Microbiologia Ambiental , Poluentes Ambientais/análise , Eucariotos/efeitos dos fármacos , Fungos/efeitos dos fármacos , Dados de Sequência Molecular , Plantas/efeitos dos fármacosRESUMO
Arsenic resistance determinants from 42 environmental bacterial isolates (32 Gram negative) were analyzed by DNA: DNA hybridization using probes derived from Escherichia coli and Staphylococcus plasmid or chromosomal arsenic resistance (ars) genes. In colony hybridization assays, 11 and 1 Gram negative strains hybridized with the E. coli chromosome and plasmid probes, respectively. No hybridization was detected using a probe containing only the arsA (ATPase) gene from E. coli plasmid or with a Staphylococcus plasmid ars probe. From Southern hybridization tests of some of the positive strains it was concluded that homology to ars chromosomal genes occurred within chromosome regions, except in an E. coli isolate where hybridization occurred in both the chromosome and a 130-kb plasmid. Our results show that DNA sequences homologous to E. coli ars chromosomal genes are commonly present in the chromosomes of environmental arsenic-resistant Gram negative isolates.
Assuntos
Arsenicais/farmacologia , Bactérias/genética , Proteínas de Bactérias , DNA Bacteriano/genética , Resistência Microbiana a Medicamentos/genética , Bombas de Íon , Complexos Multienzimáticos , Fatores R/genética , Microbiologia do Solo , Adenosina Trifosfatases/genética , Arseniatos/farmacologia , ATPases Transportadoras de Arsenito , Arsenitos/farmacologia , Bactérias/efeitos dos fármacos , Cromossomos Bacterianos/genética , Escherichia coli/genética , México , Hibridização de Ácido Nucleico , Poluentes do Solo/farmacologia , Transativadores/genéticaRESUMO
We designed PCR primers by comparison of the deduced amino acid sequences of several ornithine decarboxylase (ODC) genes. They were used to amplify fragments homologous to these genes from several dimorphic fungi. These were sequenced and the deduced amino acid sequences were compared with the corresponding regions of ODCs from different sources. Fungal ODCs fell into a compact group, well separated from the ODCs of other taxa. Sequence homology among fungal enzymes corresponded to their taxonomic position. Interesting patterns of amino acid conservation in ODCs from fungi, distinct from other organisms, were detected.