Importance of the nitrogen cycle in the deep subsurface of the Iberian Pyrite Belt

Although Darwin predicted life in the deep subsurface we need almost 200 years to prove that he was right. Most of the scarce geomicrobiological information from the continental subsurface has been obtained from artesian wells, which although interesting they do not allow to generate information about the operability of the involved biogeochemical cycles due to the lack of information on the interaction of the detected microorganisms with the mineral substrates. The information accumulated on the geomicrobiology of the Río Tinto basin during the last 35 years allow to question the extended notion that the extreme conditions detected in the river are the product of the mining activity operating in the area in the last 5000 years. The alternative model that we sustain is that the extreme conditions of the river are the consequence of the operation of a subterranean bioreactor feed with the high concentration of metallic sulfides of the Iberian Pyrite Belt (IPB). With the aim of proving its existence two drilling campaigns, MARTE (2003-2005) and IPBSL (2011-2015) were developed to intersect the bioreactor and to identify the metabolic diversity involved in the generation of the extreme conditions detected in the river. In this communication we will analyze in depth the metabolic models generated by the IPBSL project using many different techniques, in which the unexpected importance of the nitrogen cycle in the deep subsurface of the IPB has to be underlined.