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A new study of microbes in hypersaline water shows that life can survive in conditions previously thought to be uninhabitable. The research expands the possibilities for detecting life
A new study of microbes in hypersaline water shows that life can survive in conditions previously thought to be uninhabitable. The research expands the possibilities for detecting life in our solar system and shows how changes in salinity can affect life in aquatic habitats on Earth.
The research is part of a larger collaboration called Oceans Across Space and Time, led by Britney Schmidt, professor of astronomy and Earth and Atmospheric Sciences at the Cornell College of Engineering Arts and Sciences. The project is funded by NASA’s Astrobiology Program, which aims to understand how ocean worlds and life co-evolved to produce visible signs of life, past or present.
A new study titled “Single Cell Analysis in Hypersaline Solutions Predicts the Water Activity Limit of Microbial Anabolic Activity,” recently published in the journal Science Developments. This analysis is based on analysis of metabolic activity in thousands of individual cells found in the brines of industrial ponds off the coast of Southern California, where water is evaporated from seawater to collect salt.
A Stanford University-led study expands our understanding of the potential habitable space in our solar system and the implications of some terrestrial aquatic habitats becoming saltier as a result of drought and water outflow.
“Salty environments have been observed throughout the solar system, from Mars to Jupiter’s moon Europa. “Understanding how microbes interact and survive in such environments on Earth is critical to finding life elsewhere,” Schmidt said.
Scientists interested in discovering life outside Earth have long studied salty environments, knowing that liquid water is essential for life and that salt allows water to remain liquid over a wider range of temperatures. Salt can also preserve signs of life, such as pickles in brine.
A multi-institutional team collected samples from the South Bay Salt Works, home to some of the saltiest waters on Earth. They filled hundreds of bottles with brine from pools of varying salinity at salt works and then analyzed them.
Most microbes stop dividing below a water activity level of 0.9 (the amount of water available for biological reactions that allow microbes to grow), and the absolute lowest water activity level reported to support cell division in the laboratory is just above 0.63. Researchers predicted a new limit for life, suggesting that life could be active at 0.54 levels.
Previous studies investigating the limit of life’s water activity have used pure cultures to find the point at which cell division stops; This marked the end of life. But in these extreme conditions, life very slowly doubles in size. And studies of cell division don’t show when life dies; in fact, cells can be metabolically active and still very much alive even if they are not proliferating.
Instead, researchers used the cell activity limit as a more flexible definition of life because it considers cell formation as well as cell division to be a hallmark of life.
In hundreds of samples of brine, some so salty and thick as syrup, they determined water activity levels and how much carbon and nitrogen (if any) was incorporated into the cells in the brine. With this approach, they were able to detect that a cell increased its biomass by only half of 1%. In contrast, traditional methods targeting cell division can only detect biological activity after roughly doubling the biomass of cells. Scientists then predicted when this process would stop completely based on how this process slowed down as water activity decreased.
The research challenges previous views on how water limits activity for life. Although most microbes stop dividing at water activity levels below 0.9, this study shows that life can be active even at 0.54. By focusing on cellular activity, including cell construction, the researchers were able to detect signs of life in conditions where traditional methods are inadequate.
Source: Port Altele
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