"Microbial processes in subsurface ecosystems are of increasing interest due to their implications for mankind, in regards to energy, climate and health. However, these ecosystems are among the least understood. The Iberian Pyritic Belt (IPB), located in southwestern Spain is one of the largest sulfide deposits on Earth. It is of tremendous interest due to its high concentrations of metals (As, Fe, Cu, Zn, Mn, Cr, Ni ..), and constant low pH (mean 2.3) in ground and surface waters. This has been largely attributed to mining practices over the last 5,000 years. However, recent evidence points to subsurface microbial processes contributing significantly to the oxidative processes that lead anomalous metal concentrations and low pH. Next to nothing is known about microorganisms and the processes they mediate in this system. The sulfur cycle occupies a central role in the biogeochemical pathways that occur in this ecosystem. Therefore, the goal of this project is to conduct a multidisciplinary study into the role microorganisms play in the cycling of sulfur, and implications of this on the local geology and groundwater geochemistry within the IPB. This project will innovatively combine tools that span engineering, geology, geochemistry and microbiology to achieve the following: (1) Identify regions where the oxidation of sulfides, both pyritic and non pyritic and the reduction of sulfate are occurring. (2) Determine the relationship between microbial community structure and underlying geochemical changes. (3) Determine microorganisms, mechanisms, and factors controlling pyrite oxidation, sulfide oxidation and sulfate reduction. (4) Develop a geomicrobial model for the sulfur cycle and it affects on local geology and groundwater geochemistry in the IPB. This project responds to key targets set by FP7: It will contribute to the competiveness of European science by promoting the transfer of knowledge, and by engaging in timely, innovative and novel research."