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Microbialites are organo-sedimentary structures formed as minerals precipitate due to the metabolic activity of microorganisms. They can be differentiated by their internal mesostructure into strom...

The objective of this work was to modify minimally two agro-industrial wastes, to evaluate their effectiveness for the retention of copper in soils contaminated by mining tailings, as well as to evaluate the changes in the chemical forms of the metal in the soil and thus also evaluate the attenuation of copper desorption in a short period after a mine tailing spill on the soil. The solid wastes of olive mill and grape stalks of the wine-making process were modified minimally, through washing processes and partial alkalization, to obtain substrates with greater capacity for copper sorption. Two agricultural soils near a tailing impoundment were studied: a sandy loam soil with pH close to neutral and high total and available copper content and a clay soil with low copper content, slightly acid pH, and high clay content. Both soils were treated with mine tailings from the same site to simulate an involuntary spill of mining waste. The contaminated soils were treated with the organic amendments to study the sorption, desorption, and distribution of Cu in a period of 30 days. The application of simple procedures such as alkalinization or washing of the agro-industrial wastes improved the Cu sorption capacity and facilitated the application of these materials to the soil. The application of mine tailings to the soils decreased the Cu sorption and the affinity of the substrate for the metal. This adverse effect was ameliorated by the incorporation of minimally treated olive mill wastes and grape stalks, increasing the sorption by a range of 15 to 75% compared to untreated soils. In substrates with sandy loam soil, both amendments decrease the soluble fraction of Cu, an effect that was not observed in clay soil. In parallel, both amendments increased the fraction of metal bound to the oxidizable fraction, an effect that was greater for grape stalks. The organic amendments used in this study were effective to reduce the initial contamination by copper after a spill of mine tailing wastes containing this metal. In this sense, both amendments applied to sandy loam soil increased the organic matter content and the Cu sorption capacity, effects that are maintained for at least 30 days. In clay soil, these effects were observed only for grape stalks, probably due to its greater metal sorbent capacity compared to the olive oil waste.

Stromatolites are organo-sedimentary structures found principally in seas and saline lakes that contain sheets of sediments and minerals formed by layers of microbial communities, which trap sediments and induce the precipitation of minerals.A living stromatolite from the alkaline Laguna Interna in the Salar de Atacama was collected and one of the fragments was deposited in an experimental aquarium for 18 months. We used Illumina sequencing of PCR-amplified V4 regions of 16S rRNA genes from total extracted DNA to identify the microbial populations. The chemical structure was studied using X-Ray Diffraction (XRD) and bench chemical methods. We found that members belonging to the Proteobacteria, Planctomycetes, Chloroflexi and Bacteroidetes phyla dominated the bacterial communities of the living and aquarium cultured samples. The potential metabolic functionality of the prokaryotic community reveals that sulfur, nitrogen, methane and carbon fixation metabolism functions are present in the samples. This study is the first to provide new insights into the prokaryotic community composition from this unusual aquatic desert site. Further studies will be helpful to obtain a better understanding of the biotic and abiotic mechanisms residing in stromatolites from Laguna Interna, as well as to have better knowledge about the formation of these biosignatures.

The high levels of sulfate and the metals in acid mine drainages generate important environmental problems. This paper describes the synergistic combination of a biosorption process and a new sulfate removal process. The treatment for the elimination of metals by biosorption with a Bacillus strain allowed reducing the high metal concentrations that had a toxic effect on the sulfate-reducing bacteria (SRB). On the other hand, the sulfate removal process used a microbial sulfate-reducing halotolerant consortium, which was able to reduce the sulfate concentration using low-cost organic substrates such as spirulina, cellulose and industrial starch. Independent of substrate present in the culture medium, the SRB was the predominant group. The sulfate-reducing consortium was cultured on a bench-scale upflow anaerobic packed bed bioreactor filled with Celite R-635. It was possible to reduce the concentration of sulfate in the culture medium in batch or semi-continuous operation. This integrated process is an inexpensive alternative for the elimination of metals by biosortion and the elimination of sulfate using a sulfate-reducing consortium.

Sulfate is a pollutant present in the mining waste water and acid mine drainage. High levels of sulfate can generate important environmental problems. One of the alternatives proposed for the treatment of water with high levels of sulfate is the use of sulfate-reducing microorganisms. This work describes the synergistic combination of a treatment system for the removal of metals by biosorption with the strain Bacillus sp. NRRL-B-30881 to reduce the inhibiting concentration of metals in waters, followed by a new process of sulfate removal that uses a halotolerant sulfate-reducing microbial consortium. The results show that the sulfate reducing consortium can be cultured and is able to reduce the sulfate concentration using cheaper complex organic substrates like spirulina, cellulose and industrial starch. The sulfate reducing consortium was cultured on a bioreactor with Celite R-635, as support material. Using this bioreactor it was possible to reduce the sulfate concentration in the culture medium in batch or semi-continuous operation. An acid mine drainage was pretreated by lime and treated by biosortion in order to increase the pH and reduce the heavy metals concentration. Subsequently the remaining sulfate was removed by the developed process. This integrated biological process represents a more economical alternative for the removal of metal by biosortion and the removal of sulfate using a sulfate reducing consortium.

Metal removal by seven strains of Bacillus and Micrococcus was investigated. The culture age of the cells had little or no effect on their sorption capacity. Using the Langmuir isotherm, it was possible to determine that Bacillus subtilis ATCC 6633 had the highest maximum sorption capacity for uranium while a Micrococcus sp. strain presented the highest affinity. pH of the solution affected the sorption of uranium, copper, cadmium and zinc by B. subtilis. Hydrochloric acid was effective for desorption of uranium from pre‐loaded biomass. The presence of other ion inhibited uranium sorption in the following order: Cu2+>Zn2+>Mg2+Cd2+>Ca2+>K+.

Azotobacter vinelandii was better than eitherDerxia gummosa orRhizobium trifolii for sorption of UO 2 2+ . Its maximum binding capacity was 0.25 mmol UO 2 2+ /g dry biomass with an affinity constant of 333 l/mmol at pH 4.1 according to the Langmuir model. In a semisynthetic medium,A. vinelandii showed the highest sorption capacity in the early stationary phase. The binding of UO 2 2+ , Cu2+, Ca2+ and Zn2+ was affected by the pH of the solution. With HCl as eluent, virtually all the sorbed UO 2 2+ was released. The presence of Cu2+, Cd2+, Ca2+, and Zn2+ inhibited the UO 2 2+ biosorption whereas Mg2+ and K+ had no effect.