Bivalent copper ions presence triggers removal and homeostatic mechanisms in the metal-resistant microorganism Apiotrichum loubieri M12.

Microorganisms, especially those habiting mining environments, are of great importance for the retention of toxic metals in the environment. This work aimed to isolate a copper removing-microorganism from sediments of an Acid Mine Drainage-affected environment and to study the cellular responses trigger by metal presence. Apiotrichum loubieri M12 was able to tolerate and remove Cu(II) from liquid culture media, reaching a 30-35% removal capacity when it was exposed to 40 µg mL-1 Cu(II) after 48 h. Analysis of the biomass exposed to the metal through SEM-EDS showed copper presence on the cell surface and variations in the proportion of other biomass constituent elements. Proteomics revealed that the presence of Cu(II) induces differential expression of intracellular proteins involved in a wide variety of metabolic processes. Interestingly, a specific response to the metal was detected in cell-free supernatants, in which copper binding proteins were identified. A large number of proteins with metal ion binding sites were detected both at intra and extracellular levels. The microorganism responds not only by adjusting intracellular protein expression, but also by adjusting expression of proteins in the extracellular space.

Characterization of copper stress response in Fusarium tricinctum M6: A metal-resistant microorganism isolated from an acid mine drainage-affected environment.

Acid mine drainage-affected environments are interesting microbial niches for the isolation of metal-resistant microorganisms. In this sense, the aim of the present work is to isolate and characterize metal-resistant microorganisms from sediments of an abandoned gold mine located in San Luis (Argentina). For these purposes, the metal removal capacity and the microelemental composition of the biomass exposed to metals were evaluated. Likewise, proteomic techniques were applied to understand the removal and resistance mechanisms. Fusarium tricinctum M6 was isolated and identified as tolerant to Cu(II), Fe(II) and Cr(VI). When faced with 40 µg mL-1 Cu(II), the growth was affected by 60% and the removal capacity was 30-35%. Copper was found uniformly distributed in the biomass (5.23% w/w) and variations in the proportion of other biomass constituent elements were detected. When exposed to Cu(II), F. tricinctum M6 showed differential expression of intra and extracellular proteins involved in different metabolic processes. A large number of proteins with metal ion binding sites were detected both at intra and extracellular levels. The results obtained in the present work indicated bioadsorption of the metal on the cell surface and an important readjustment of the protein expression to counteract the stress produced by Cu(II).

Impact of anthropogenic activities on an urban river through a comprehensive analysis of water and sediments.

The aim of this study was to assess the impact of urban and industrial areas on an urban river through a comprehensive analysis of water and sediments. Six different sites along the San Luis River, Argentina, were characterized by measuring 12 physical-chemical parameters and nine heavy metals according to standard protocols. Metal pollution in sediment samples was evaluated with several indices. Cluster analysis was applied to standardized experimental data in order to study spatial variability. As, Cu, Cr, Mn, Pb, and Zn were the main contributors to sediment pollution, and the industrial zone studied showed moderate enrichment of Co, Cu, and Zn, probably due to anthropogenic activities. Cluster analysis allowed the grouping of the sites: sediment samples were classified into two clusters according to the metal content; water samples were arranged into three groups according to organic matter content. The results were compared with sediment and water quality guidelines. They indicated progressive deterioration of water and sediment quality compared with the background area, mainly in the sites following the industrial park and domestic discharge areas. Moreover, the results showed that the analysis of both water and sediment should be considered to achieve a watershed contamination profile.

The potential application of an autochthonous fungus from the northwest of Argentina for treatment of sugarcane vinasse.

Vinasse is a waste material from distillery industries, which causes major environmental problems around the world. Argentina alone produces about 4 billion liters of vinasse annually; consequently, diverse biological eco-friendly treatments are evaluated for their ability to reduce the detrimental effects. The present study reports on the degradation of a 50% (v/v) local vinasse sample by an autochthonous fungus identified as Aspergillus sp. V1. The Bioprocess was conducted for 15 d at 30 °C after inoculation of spores at an end concentration of 1 × 106 CFU/mL. Effluent neutralization was detected after 6 d of treatment, with maximum COD and BOD removal after 12 d (49% and 59%, respectively). Effects of vinasse before and after treatment were predicted using Caco-2 cells and Triticum aestivum L. (wheat) seeds as toxicological indicators. Only 13% viability was observed for Caco-2 cells exposed to untreated vinasse, but this percentage increased more than 3-fold for cells exposed to the treated effluent. While vinasse without treatment completely inhibited germination of seeds, exposure to treated effluent demonstrated a germination percentage of 60%. The present study highlights the use of a dual-purpose biotechnological process that aimed at reducing the detrimental effects of vinasse, enhancing its quality for agricultural practices.

Simultaneous chromate and sulfate removal by Streptomyces sp. MC1. Changes in intracellular protein profile induced by Cr(VI).

The purpose of this study was to investigate the influence of increasing sulfate concentrations on chromium removal, to evaluate the effect of the presence of Cr(VI) on sulfate removal by Streptomyces sp. MC1 and to analyze the differential protein expression profile in the presence of this metal for the identification of proteins repressed or overexpressed. In the presence of Cr(VI) but in the absence of sulfate ions, bacterial growth was negligible, showing the Cr(VI) toxicity for this bacterium. However, the sulfate presence stimulated bacterium growth and Cr(VI) removal, regardless of its concentrations. Streptomyces sp. MC1 showed ability to remove chromium and sulfate simultaneously. Also, the sulfate presence favored the decrease of total chromium concentration from supernatants reaching a decrease of 50% at 48 h. In presence of chromium, seven proteins were down-expressed and showed homology to proteins involved in protein biosynthesis, energy production and free radicals detoxification while two proteins involved in oxidation-reduction processes identified as dihydrolipoamide dehydrogenase and S-adenosyl-l-methionine synthase were overexpressed.

Production of bioemulsifiers by Amycolatopsis tucumanensis DSM 45259 and their potential application in remediation technologies for soils contaminated with hexavalent chromium.

In recent years, increasing interest has been shown in the use of bioemulsifiers as washing agents that can enhance desorption of soil-bound metals. However, high production costs derived from the use of expensive substrates for formulation of the fermentation media represent the main challenge for full, large-scale implementation of bioemulsifiers. This work reports on a first study of bioemulsifier production by the actinobacterium Amycolatopsis tucumanensis DSM 45259 using different carbon and nitrogen sources. Preliminary results on the potential use of these compounds as washing agents for soils contaminated with Cu(II) and Cr(VI) are also presented. The best specific production was detected using glycerol and urea as carbon and nitrogen substrates, respectively. However, with all of the substrates used during the batch assay, the bioemulsifiers showed high levels of stability at extreme conditions of pH, temperature, and salt concentration. Under the current assay conditions, the bioemulsifiers were not effective in removing Cu(II) from soil. However, they were able to mediate Cr(VI) recovery, with the removal percentage doubled compared to that seen when using deionized water. These findings appear promising for the development of remediation technologies for hexavalent chromium compounds based upon direct use of these microbial emulsifiers.

Production and partial characterization of bioemulsifier from a chromium-resistant actinobacteria.

Surface-active compounds such as synthetic emulsifiers have been used for several decades, both for the degradation of hydrocarbons and increasing desorption of soil-bound metals. However, due to their high toxicity, low degradability, and production costs unaffordable for use in larger ecosystems, synthetic emulsifiers have been gradually replaced by those derived from natural sources such as plants or microbes. In previous studies, the bacterium Streptomyces sp. MC1 has shown the ability to reduce and/or accumulate Cr(VI), a highly promising advance in the development of methods for environmental clean-up of sites contaminated with chromium. Here, new studies on the production of emulsifier from this strain are presented. The cultivation factors that have a significant influence on emulsifier biosynthesis, as well as the interactions among them, were studied by factorial design. Based upon optimization studies, maximum bioemulsifier production was detected in the culture medium having an initial pH of 8 with phosphate 2.0 g L(-1) and Ca(+2) 1.0 g L(-1) added, with an emulsification index about 3.5 times greater compared to the basal value. Interestingly, in the presence of 5.0 g L(-1) Cr(VI), Streptomyces sp. MC1 retained about 65% of its emulsifier production ability. Partially purified emulsifier presented high thermo-stability and partial water solubility. These findings could have promising future prospects for the remediation of organic- and metal-contaminated sites.