Beneath our feet, crouched in the hard rock that supports us, there is an enormous variety of life capable of surviving without oxygen, liquid water and light. According to our guest, Ricardo Amils, a senior researcher at the Center for Astrobiology, these creatures constitute, according to certain authors, 80% of the microbial biodiversity of the Earth. Investigating their existence not only helps to understand the tiny inhabitants of our planet, but also opens a window to the possibility that a similar type of life exists in other places, such as Mars, for example. On the surface of the Red Planet, named for the color reflected by the abundance of iron oxides in the terrain, cosmic radiation is lethal to any living being that tries to survive in the open air, but in the depths that radiation cannot penetrate and well there could be some kind of life clinging to the hard rock. Microorganisms like this do exist on Earth, as Ricardo Amils and a large group of researchers have demonstrated thanks to a project that, for 10 years, has drilled and extracted information on the biodiversity that populates an underground layer rich in iron ore and sulfur known as the Iberian Pyrite Belt.
It is the name by which a vast concentration of massive sulphides is known that extends throughout a large part of the south of the Iberian Peninsula. It is about 250 km long and 30 to 50 km wide, ranging from the area of Alcácer do Sal (Portugal) to the province of Seville (Spain).
The Iberian Pyrite Belt is a layer rich in pyrite, an iron sulfide, and other metallic minerals that formed 350 million years ago due to a period of high volcanic activity that took place in a large part of the southern Iberian Peninsula. The strip is more than 250 kilometers long and up to 50 km wide and extends at various depths throughout the region. One of the most emblematic places related to the Iberian Pyrite Belt is Río Tinto, in Huelva, a place where, thanks to a long mining activity, waters with a high iron and sulfuric acid content emerge, giving it a color reminiscent of red wine. . There exists a biology that is adapted to extreme conditions, toxic for the majority of living beings. Some researchers think that the special conditions were due to mining activity but others argue that it is due to the activity of certain hidden microorganisms in the primordial rock.
To corroborate this second hypothesis, in 2012 an investigation began as part of the project IPBSL (Iberian Pyrite Belt Subsurface Life Detection) financiado por Euroepan Research Council (ERC). Thanks to the funds received, it was possible to carry out a drilling campaign to extract samples from the Iberian Pyrite Belt in different places and at different depths. The rock cores obtained since then have allowed the study of the existing microorganisms in the hard rock located up to more than 600 meters deep.
Different applied methods have managed to demonstrate the existence of microorganisms whose activity had never been observed before, as well as the existence of biofilms that were considered improbable given the limiting energy conditions existing in the subsoil.
The sequencing of the existing genetic fingerprints in the samples has revealed that in the hard rock, in the absence of light, there is a great biodiversity of organisms that form what we have called the “dark biosphere”.
The team to which our guest, Ricardo Amils belongs, has managed to demonstrate the existence of microbes capable of oxidizing iron in the absence of oxygen, generating in the process the soluble iron and sulfuric acid that appear in the acid and corrosive waters of Rio Tinto.
Using the most advanced techniques, the researchers have managed to identify and observe in the laboratory 17 different types of microorganisms, the “main 17”, says Ricardo Amils in the interview.
These results not only speak of the existence of this dark biosphere on our planet, but also raise the possibility that life with similar characteristics also exists on Mars and other bodies in the Solar System.
I invite you to listen to Ricardo Amils, Emeritus Professor of Microbiology at the Autonomous University of Madrid and Senior Researcher at the Center for Astrobiology.
References:
Active microorganisms in the deep subsoil of the Iberian Pyrite Belt reveal the origin of the extreme conditions of the Tinto River.
Ricardo Amils, Cristina Escudero, Monike Oggerin, Fernando Puente Sánchez, Alejandro Arce Rodríguez, David Fernández Remolar, Nuria Rodríguez, Miriam García Villadangos, José Luis Sanz, Carlos Briones, Mónica Sánchez, Felipe Gómez, Tania Leandro, Mercedes Moreno-Paz, Olga Prieto-Ballesteros, Antonio Molina, Fernando Tornos, Irene Sánchez-Andrea, Kenneth Timmis, Dietmar H. Pieper, Victor Parro (2022) Coupled C, H, N, S and Fe biogeochemical cycles operating in the deep subsurface of the Iberian Pyrite Belt . Environ Microbiol doi:10.1111/1462-2920.16291