A new molecular DNA analysis technique has made it possible to detect live microbes at depths of up to 4.20 metres. This discovery also has implications for the search for extraterrestrial life. Historically, the arid lands of Chile’s Atacama Desert were thought to be devoid of life. However, in one of the driest regions, a group of researchers led by Lucas Horstmann and Dirk Wagner from the German Geosciences Research Center GFZ, in collaboration with colleagues from the Technical University of Berlin and the University of Antofagasta in Chile, discovered something previously unknown. underground living space.
This was based on recently developed molecular DNA analysis techniques that allow targeted isolation and analysis of intracellular DNA. It consists of intact cells of living or dormant organisms and allows the detection of live and potentially active microbial communities living in extremely arid soils at depths of up to 4.20 metres. Thus, the study published in the journal PNAS PortIt expands our understanding of the biodiversity of a region where conditions of extreme drought, salinity and nutrient scarcity are close to the limits of life. The results also have implications for the search for life on other planets.
Background: A spectacular desert
Deserts are one of the largest and most fragile ecosystems in the world. Although the conditions here are among the harshest and most dangerous for life, it is a haven for microbial life. In the absence of regular rainfall, microorganisms that mediate nutrient flow and use soil components such as minerals and salts and atmospheric gases as energy and water sources are the most important ecological component.
“The study of microbial diversity and distribution is crucial to fully understand the central role of microbial processes in maintaining the ecological balance and functionality of desert ecosystems, especially for their future development in the context of climate change,” says Dirk Wagner. from GFZ’s Department of Geomicrobiology and one of the leaders of the study.
The Atacama Desert in northern Chile is considered the driest hot desert in the world with an area of 105,000 square kilometers. Therefore, it is an extremely convenient and suitable place to study this habitat. Shallow areas with a depth of about one meter have already been explored. Here, we know that this is a niche habitat that provides protection against UV radiation and where water is still available for microbial life to thrive.
A New Approach: Analyzing Deep Soils in the Atacama Desert Using Special DNA Analysis
On the other hand, deeper layers of desert soils have been analyzed in only a few studies to date. They were therefore the focus of a team led by doctoral student Lucas Horstmann and postdoctoral researcher Daniel Lipus in the Geomicrobiology department of the GFZ, as well as Dirk Wagner, head of the same department and professor of Geomicrobiology and Geobiology. University of Potsdam. Our other colleagues came from TU Berlin and the University of Antofagasta in Chile. The researchers wanted to test whether the deeper sediments of the ultra-arid Atacama Desert were also a habitat for specialized microbes.
The research team studied a soil profile in the Yungay region, approximately 60 kilometers southeast of Antofagasta, to analyze microbial diversity and its interaction with soil properties along a depth profile that included both playa deposits and alluvial cone deposits below, reaching depths of 4. 2 meters. To do this, they excavated a soil profile and took soil samples every 10 centimeters to a depth of three meters, then every 30 centimeters, which were taken to the GFZ laboratory for analysis.
The scientists used a new molecular DNA analysis technique developed by Dirk Wagner and other GFZ collaborators to detect traces of life in the samples: only intracellular DNA can be filtered using a special extraction method. sample, i.e. DNA obtained from intact and potentially active cells. Various chemicals, centrifuges and filters are used for this.
“This approach is a significant advance for microbial diversity studies under extreme conditions because it effectively eliminates the bias introduced by DNA from dead cells and still provides reliable data even if the detection limit of other methods has been reached due to low biomass,” emphasizes Wagner.
Detection of a potentially viable microbial community at a depth of 4.2 meters
By extracting intracellular DNA and subsequent gene sequencing of the samples, the researchers were able to identify potentially viable microbes at a depth of 4.2 meters. Microbes of the Firmicutes type were mainly found in the upper 80 centimeters, but their numbers decreased as depth increased, and thus the amount of soluble salts also increased. Researchers suspect that high salt concentrations and increasing water scarcity may be the reason for the end of microbial colonization at the bottom of playa sediments. In this regard, their findings are consistent with previous research.
But Horstmann and Wagner’s team rediscovered the microbial community in alluvial cone deposits below two metres. It is more diverse than the surface community and is probably completely isolated from the surface. It consisted of bacteria belonging to the phylum Actinobacteriota, a group with specialized members found mostly in dry or virgin soils.
The presence of these microbes may be associated with the presence of vesicular gypsum dissolved in anhydrite, which could be an alternative water source. The organisms observed in this study are species that can use trace gases such as hydrogen as an energy source to use CO2 as a carbon source for their growth.
“This type of metabolism, called chemolitoautotrophy, has been suggested by other studies to be important in extremely arid soils where organic matter as a carbon source is extremely limited. Therefore, it may also be important for the isolated underground niches investigated in this study,” says first author Lukas Horstmann.
Summary and Outlook: Amazing Desert Biodiversity and Implications for Extraterrestrial Life
“The discovery of this subterranean community, which thrives in alluvial cone sediments at depths below two meters and exhibits extraordinary diversity and ecological stability, challenges our current understanding of desert ecosystems,” concludes Horstman.
The authors suggest that this community may have colonized the land as early as 19,000 years ago, before being buried by playa sediments, and they suggest that it may have continued downward for an unknown distance, representing a previously unknown deep biosphere beneath the extremely arid desert soils. .
“Given the widespread distribution of arid lands on our planet, the presence of potentially carbon-fixing communities in previously unexplored subsurface soils has profound implications not only for biodiversity in deserts but also for elemental cycling on a global scale,” says co-author Dirk. Wagner. “This shows that the importance of these habitats has been underestimated until now. It underlines the importance of subsurface habitats for a full understanding of desert ecosystems in the future.”
The researchers emphasize that the results of this study not only have implications for our planet Earth, but are also relevant to current discussions on the search for life on other planets: “The existence of gypsum deposits similar to those found in alluvial cones on Mars. deposits are of great interest from the point of view of astrobiology. This surface at Atacama “The association of gypsum communities with gypsum substrates may provide further evidence that gypsum deposits on Mars not only indicate the possibility of liquid water in the past, but may also serve as a habitable niche for microbial life today.”
Source: Port Altele
