RESUMEN
The chemical synthesis of monoatomic metallic copper is unfavorable and requires inert or reductive conditions and the use of toxic reagents. Here, we report the environmental extraction and conversion of CuSO4 ions into single-atom zero-valent copper (Cu0) by a copper-resistant bacterium isolated from a copper mine in Brazil. Furthermore, the biosynthetic mechanism of Cu0 production is proposed via proteomics analysis. This microbial conversion is carried out naturally under aerobic conditions eliminating toxic solvents. One of the most advanced commercially available transmission electron microscopy systems on the market (NeoArm) was used to demonstrate the abundant intracellular synthesis of single-atom zero-valent copper by this bacterium. This finding shows that microbes in acid mine drainages can naturally extract metal ions, such as copper, and transform them into a valuable commodity.
RESUMEN
A heavy-metal resistant bacterial consortium was obtained from a contaminated river in São Paulo, Brazil and utilized for the design of a fixed-bed column for the removal of copper. Prior to the design of the fixed-bed bioreactor, the copper removal capacity by the live consortium and the effects of copper in the consortium biofilm formation were investigated. The Langmuir model indicated that the sorption capacity of the consortium for copper was 450.0 mg/g dry cells. The biosorption of copper into the microbial biomass was attributed to carboxyl and hydroxyl groups present in the microbial biomass. The effect of copper in planktonic cells to form biofilm under copper rich conditions was investigated with confocal microscopy. The results revealed that biofilm formed after 72 h exposure to copper presented a reduced thickness by 57% when compared to the control; however 84% of the total cells were still alive. The fixed-bed bioreactor was set up by growing the consortium biofilm on granular activated carbon (GAC) and analyzed for copper removal. The biofilm-GAC (BGAC) column retained 45% of the copper mass present in the influent, as opposed to 17% in the control column that contained GAC only. These findings suggest that native microbial communities in sites contaminated with heavy metals can be immobilized in fixed-bed bioreactors and used to treat metal contaminated water.
Asunto(s)
Reactores Biológicos/microbiología , Cobre/aislamiento & purificación , Consorcios Microbianos , Adsorción , Bacterias/efectos de los fármacos , Bacterias/crecimiento & desarrollo , Bacterias/ultraestructura , Biodegradación Ambiental/efectos de los fármacos , Biopelículas/efectos de los fármacos , Brasil , Carbón Orgánico/farmacología , Concentración de Iones de Hidrógeno , Cinética , Consorcios Microbianos/efectos de los fármacos , Espectrometría por Rayos X , Espectroscopía Infrarroja por Transformada de Fourier , TemperaturaRESUMEN
We developed a multi-locus quantitative PCR approach to minimize problems of precision, sensitivity and primer specificity for quantifying a targeted microbial group in nature. This approach also avoids a systematic error in population quantitation when 16S rRNA genes are used because of copy number heterogeneity. Specific primers were designed to assess the abundance of psychrotrophic and mesophilic Exiguobacterium spp. that excluded the thermophilic members of the genus. The chosen primers targeted genes for DNA gyrase B (gyrB), the beta subunit of the RNA polymerase gene (rpoB) and a hypothetical gene so far found only in this group. The results demonstrate that the multiple primer approach provides a more reliable estimate of population density; that the targeted Exiguobacterium group is found at a median density of 50,000 gene copies per mug of total community DNA in 27 of 29 permafrost soils but was found in only one of the four temperate and tropical soils tested.
Asunto(s)
Bacillaceae/aislamiento & purificación , Proteínas Bacterianas/genética , ARN Polimerasas Dirigidas por ADN/genética , Hielo , Reacción en Cadena de la Polimerasa/métodos , Microbiología del Suelo , Bacillaceae/clasificación , Bacillaceae/genética , Bacillaceae/crecimiento & desarrollo , Bacterias/clasificación , Bacterias/genética , Bacterias/aislamiento & purificación , Girasa de ADN/genética , Cartilla de ADN , ADN Bacteriano/análisis , Ecosistema , Filogenia , Siberia , Especificidad de la EspecieRESUMEN
Three Gram-positive bacterial strains, 7-3, 255-15 and 190-11, previously isolated from Siberian permafrost, were characterized and taxonomically classified. These microorganisms are rod-shaped, facultative aerobic, motile with peritrichous flagella and their growth ranges are from -2.5 to 40 degrees C. The chemotaxonomic markers indicated that the three strains belong to the genus Exiguobacterium. Their peptidoglycan type was A3alpha L-Lys-Gly. The predominant menaquinone detected in all three strains was MK7. The polar lipids present were phosphatidyl-glycerol, diphosphatidyl-glycerol and phosphatidyl-ethanolamine. The major fatty acids were iso-C13:0, anteiso-C13:0, iso-C15:0, C16:0 and iso-C17:0. Phylogenetic analysis based on 16S rRNA and six diverse genes, gyrB (gyrase subunit B), rpoB (DNA-directed RNA polymerase beta subunit), recA (homologous recombination), csp (cold shock protein), hsp70 (ClassI-heat shock protein-chaperonin) and citC (isocitrate dehydrogenase), indicated that the strains were closely related to Exiguobacterium undae (DSM 14481(T)) and Exiguobacterium antarcticum (DSM 14480(T)). On the basis of the phenotypic characteristics, phylogenetic data and DNA-DNA reassociation data, strain 190-11 was classified as E. undae, while the other two isolates, 7-3 and 255-15, comprise a novel species, for which the name Exiguobacterium sibiricum sp. nov. is proposed.