Microbial spores are highly resistant resting states developed by certain bacteria to tolerate unfavorable environmental conditions. Research in spore-forming bacteria has been carried out mainly in the medical field, while the environmental role and metabolic diversity of spore-forming bacteria have remained relatively unexplored. Recently, spore-forming bacteria have been detected as dominant members of the microbial communities in heavy metal-contaminated sites. There is emerging evidence in the literature of metal reduction by groups of spore-forming microorganisms (e.g. Desulfotomaculum spp., Clostridium spp., Desulfosporosinus spp., and Alkaliphilus metalliredigens), supporting the idea that spore-formers contribute to the metabolism of heavy metals. Additionally, spore-forming bacteria (Desulfotomaculum spp., Carboxydothermus hydrogenoformans Z-2901, and Candidatus Desulforudis audaxviator) have been detected in microbial communities inhabiting extreme environments such as deep mines or geothermal systems. This suggests that spore-forming bacteria are not only more phylogenetically diverse than previously thought, but also that they should display a metabolic repertory that allow them to dominate microbial communities in environments with extreme conditions (e.g. high temperature, lack of electron donors, varying conditions of oxygen and moisture, high levels of hazardous elements). In addition to this, spore-forming microorganisms have been recently found dominating microbial fuel cells, which are an exciting new field of research into sustainable energy resources. Despite the contribution of spore-forming bacteria to the microbial communities in contaminated or extreme environments, and their biotechnological potential, they have been largely overlooked by traditional and molecular techniques used in microbial ecology. The aim of this proposal is to characterize the metabolic capabilities of spore-forming microorganisms in environments in which the production of spores could result in an advantage for survival (e.g. at contaminated subsurface or at high enthalpy geothermal sites). We propose to start by the isolation of spores, followed by the analysis of their metabolic capabilities through environmental genomics. Additionally, we propose to isolate and cultivate spore-forming bacteria. In both cases we expect to discover new metabolic properties that can contribute to explain the role of spore-formers in environmental samples.