The vast majority of the microorganisms of environmental samples cannot be studied in a lab because we lack the exact methods required to propagate and cultivate them, making many of them remain unknown to science until now. Nevertheless, the recent development of molecular techniques such as the massive analysis of nucleid acids and proteins of these populations has offered the opportunity of describing in detail both their biological diversity on an individual level and the metabolical networks that these organism use and which allow them to live and prosper in such selective environments. One of the most interesting microbial habitats is that formed by acid waters (pH ≤ 2), rich in metals (aluminum, arsenic, lead and others), present in mining prospections, such as those formed around an old mercury mine (Los Rueldos) located in Mieres.

Apart from drastically expanding our knowledge of life in extremely acidic environments, this research provides interesting biotechnological applications related to the decontamination of metal-rich waters or to the search of new compounds with a pharmaceutical or industrial aim.

A recent research, coordinated by reseachers from the group of Technology, Biotechnology and Environmental Geochemistry (BIOGEOAMB) of the University of Oviedo and the Institute of Catalysis, CSIC, Madrid, and published in one of the most prestigious journals related to microbial ecology (The ISME Journal, from the Nature group), has shown that the conditions of the interior of the aforementioned mine, alongside the absence of ligh and oxygen in the deepest areas of the habitat, promote very restrictive environments for higher organisms (animals and plants) to thrive, but host a microbial diversity (formed by microorganisms of the Bacteriae and Archea domains) higher to that found in other similar habitats of our planet. The acidity of the water was generated once the mine had been abandoned, due to the oxidizing action of the bacteriae on the reduced compounds of sulfur and/or iron, such as pyrite, present in the environment, alongside the absence of light and the filtrations of rain water.

Application of cutting-edge "OMICA" techniques to environmental studies

The diversity discovered is the result of the formation of protective polysaccharide structures with gelatinous consistency (biofilms) in stagnant water where the microorganisms live and where low-oxygen microenvironments also originate. The researchers applied genomic (sequencing and identification of the genes of DNA) and proteomic (analysis, identification and quantification of proteins) techniques to identify the populations of bacteriae and archae and study their metabolism, making them the first environmental smaples on which an method of direct absolute quantification of the proteins directly isolated from the environment (protemic quantitative environment) and the metaproteo-genomic study, the first conducted on the ecology of different microbial communities within the same ecosystem.

It has not been possible to give a precise taxonomic classification of the majority of the diversity of archae found in Los Rueldos, due to the novelty nature of the types detected. Another of the insteresting aspects of the system analyzed is the detection of extremely small archae (~20 nm, i.e. 0.0002 mm in diameter), which, due to their size, are located at the very limit of what is possible for life, and which had been previously described for the first time in 2006 in another acidic environment (Richmond Mine, California). The sequences of DNA of these nano-organisms indicate that they are different from the previous ones, and the detailed analysis of their reconstructed genomes will allow researchers to infer the role of these enigmatic cells in the ecosystem.

Possible biotechnological applications

The presence of microorganisms that are capable of living alongside noxious metals offers the possibility of studying their defense mechanisms to apply them in methods of biological decontamination (bioremediation) of environments that have been polluted by these metals. The researchers have proven that the polymeric matrix that makes up the biofilms, apart from providing carbohydrates for the bacterial metabolism, has a high capacity of adsorption of metals through ionic exchange, and therefore it constitutes an interesting model to design materials that are useful for cleaning contaminated waters. On the other hand, these new microorganisms are a potential source of compounds with a pharmaceutical (antibotics and/or antitumorals) and industrial (for example, new enzymes) applications.

Research team

• Celia Méndez García
• Victoria Mesa Salgado
• José Luis Rodríguez Gallego
• Ana Isabel Peláez Andrés
• Jesús Sánchez Martín
• Luis Manuel Rubio Osuna
• Iván Lores Ovies