Microorganisms living in the Atacama Desert in northern Chile – one of the driest locations on Earth – have developed a unique method of extracting life-sustaining water from their environment.
Some species of rock-inhabiting cyanobacteria are capable of pulling water from its mineral house. The findings, which are published in the Proceedings of the National Academy of Sciences, provide insight into how organisms can survive harsh surroundings lacking in or void of water – like Mars – and may inform how humans could one day also extract water from minerals readily available in these extreme environments.
Several desert-dwelling microbes are known to live inside of rocks, among them the drought-resistant cyanobacteria Chroococcidiopsis. This microorganism exists beneath a thin layer of gypsum rock, which provides protection from high solar exposure and intense winds as well as a crucial water source.
To determine how Chroococcidiopsis uses rocks as a water source, researchers collected gypsum samples from the Atacama Desert and brought them back to a US-based lab. Each sample was cut into half-millimeter cubes of rock and for 30 days, these samples were kept either in an arid or humid self-contained environment before undergoing a combination of microscopy and spectroscopy to measure the biological and geological interactions that take place in this mini habitat.
The Chroococcidiopsis placed in the humid space were able to extract water from their environment, whereas the photosynthetic microbes in the dry environment extracted water from the rock by boring into it using a biofilm produced of organic acids.
"When they were put under stressed conditions, the microbes had no alternative but to extract water from the gypsum, inducing this phase transformation in the material,” said study author David Kisailus, University of California, Irvine professor, in a statement. This biofilm spurs mineral dissolution and allows for the extraction of water in crystalized planes of water contained between calcium and sulfate ions, which further led to a transformation of the rock’s chemical makeup into anhydrite, a white dehydrated mineral consisting of calcium sulfate.
"Researchers have suspected for a long time that microorganisms might be able to extract water from minerals, but this is the first demonstration of it,” said co-author Jocelyne DiRuggiero, associate professor at Johns Hopkins University's Department of Biology. "This is an amazing survival strategy for microorganisms living at the dry limit for life, and it will guide our search for life elsewhere."
The scientists add that their findings suggest that endolithic microbes – those living in rocks – have found ways to adapt to extremely dry, seemingly inhabitable environments and provides learning opportunities for future advanced methods of water storage.