How desert microbes extract water from rocks
Scanning electron micrograph of cyanobacteria living in the gypsum rocks collected from the Atacama Desert.
Several microbes in desert environments live inside rocks. To survive, such endolithic microbes rely on the ability of rocks to retain water. However, it is unclear how microbes extract water from rocks and how such mechanisms affect rocks. Using a combination of microscopy and spectroscopy, Wei Huang et al. (pp. 10681–10687) examined colonized gypsum rocks collected in Chile’s Atacama Desert, one of the driest places on Earth. Photosynthetic microbes living inside the rocks extracted structurally ordered water from gypsum, leading to the transformation of gypsum into anhydrite. The microbes attached to high-energy crystal planes and produced a biofilm composed of organic acids. The biofilm prompted mineral dissolution and water extraction, subsequently leading to the phase transformation of the rock. X-ray diffraction showed that the dehydrated anhydrite rock existed only where microbes were populated. The authors also grew an isolated strain of cyanobacterium on gypsum samples in either the presence or absence of water during a 30-day incubation period, after which they found that only colonized gypsum with no water had transformed to anhydrite. The findings suggest that endolithic microbes have adapted to extremely dry environments, according to the authors. — M.S.
Evolutionary history of lions
The demographic and evolutionary histories of distinct populations of lions across the world are poorly understood. Marc de Manuel, Ross Barnett, et al. (pp. 10927–10934) analyzed genomic data of 20 lion specimens, including extant lions from Africa and India, lions from extinct populations that lived outside modern lions’ geographic distribution between the 15th century and 1959, and extinct Pleistocene cave lions from Siberia and the Yukon that lived approximately 30,000 years ago. The analysis suggests that cave and modern lions shared an ancestor that lived approximately 500,000 years ago. After their divergence, the lineages of cave and modern lions likely did not hybridize. The two main lineages of modern lions likely diverged approximately 70,000 years ago and exhibited subsequent gene flow. However, lions from India, which have small population sizes, exhibited little genetic diversity, coinciding with historical evidence of anthropogenic population declines after the 18th century. Previous studies have addressed the feasibility of using DNA from lions in India to restore North African lion populations, but the findings suggest that West African lions are the closest living relatives of North African lions, according to the authors. — M.S.