Oct. 29, 2012 Millions of years ago fire and water forged the gypsum rocks locked in at Cuatro Ciénegas, a Mexican valley similar to the Martian crater where NASA's Rover Curiosity roams. A team of researchers have now analysed the bacterial communities that have survived in these inhospitable springs since the beginning of life on Earth.
"Cuatro Ciénegas is extraordinarily similar to Mars. As well as the Gale crater where Curiosity is currently located on its exploration of the red planet, this landscape is the home to gypsum formed by fire beneath the seabed," as explained by Valeria Souza, evolutionary ecologist at the National Autonomous University of Mexico (UNAM).
The researcher states that sulphur components from magma and minerals from the sea (carbonates and molecules with magnesium) are required to form gypsum. In the case of the Cuatro Ciénegas Basin, the magma under the seabed was very active. In fact, it allowed for the continent displacement during the Jurassic Period: "Here was where the supercontinent Pangea opened up some 200 million years ago, pushing the hemisphere north from the equator where it is now."
In the case of Mars, the scientists have not been able to confirm tectonic movement in its crust at any point, but they believe that a large meteorite crashed into its primitive sea. The fact that probing has detected gypsum in the Gale crater indicates that mineral-rich water was present and that sulphur was able to form due to the impact of the meteorite causing the crater.
It is no easy task to find a place on Earth similar to this Martian environment, except in Cuatro Ciénegas. For this reason astrobiologists toil in their work to understand how its bacterial communities work. "This oasis in the middle of the Chihuahua desert is a time machine for organisms that, together as a community, have transformed our blue planet yet have survived all extinctions. How they have managed to do this can be revealed by their genes," says Souza.
The team have analysed the 'metagenomes', the genome of the different bacterial communities that proliferate in these marshes by adapting parallel strategies to overcome survival challenges in a place with so little nutrients.
Green, red and blue springs
The results published in the journal Astrobiology reflect the existence of two communities in different pits for example. One is 'green' and is formed by cyanobacteria and proteobacteria that have adapted to the lack of nitrogen. Another is 'red' and is made of Pseudomonas and other micro-organisms that live without hardly any phosphorus. There are also blue springs which are generally deeper and lacking in nutrients.
"Understanding the usage and exploitation strategies of phosphorus is necessary in understanding what could happen in extreme scenarios like on other planets where there is a possibly serious limitation to this and other nutrients," explains Luis David Alcaraz, Mexican researcher participating in the study from the Higher Public Health Research centre of Valencia, Spain.
This project has enjoyed the support of Mexico's Carlos Slim Foundation and the Technological Innovation Research Project Support Programme of UNAM. It has also received the support of the National Science Foundation (NSF) of the USA and NASA, which has been studying Cuatro Ciénegas for more than a decade.
The Cuatrociénegas Flora and Fauna Protection Area is a protected area but the scientists and conservation groups are worried that its water is being over exhausted. "The bacterial communities have survived all types of cataclysms here such as the extinction of the dinosaurs or the majority of marine creatures. But, the only thing they are not adapted for is the lack of water," warns Souza.
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- Nguyen E. López-Lozano, Luis E. Eguiarte, Germán Bonilla-Rosso, Felipe García-Oliva, Celeste Martínez-Piedragil, Christine Rooks, Valeria Souza. Bacterial Communities and the Nitrogen Cycle in the Gypsum Soils of Cuatro Ciénegas Basin, Coahuila: A Mars Analogue. Astrobiology, 2012; 12 (7): 699 DOI: 10.1089/ast.2012.0840
- Mariana Peimbert, Luis David Alcaraz, Germán Bonilla-Rosso, Gabriela Olmedo-Alvarez, Felipe García-Oliva, Lorenzo Segovia, Luis E. Eguiarte, Valeria Souza. Comparative Metagenomics of Two Microbial Mats at Cuatro Ciénegas Basin I: Ancient Lessons on How to Cope with an Environment Under Severe Nutrient Stress. Astrobiology, 2012; 12 (7): 648 DOI: 10.1089/ast.2011.0694
- Germán Bonilla-Rosso, Mariana Peimbert, Luis David Alcaraz, Ismael Hernández, Luis E. Eguiarte, Gabriela Olmedo-Alvarez, Valeria Souza. Comparative Metagenomics of Two Microbial Mats at Cuatro Ciénegas Basin II: Community Structure and Composition in Oligotrophic Environments. Astrobiology, 2012; 12 (7): 659 DOI: 10.1089/ast.2011.0724
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