Abstract
The high-altitude pre-Andean region of the Atacama Desert, is characterized by its stark volcanic rock formations, hosts unique hydrothermal gypsum outcrops (gypcrete). This study delves into the biomolecular composition of endolithic phototrophic microbes thriving within these gypcretes. Using advanced Raman spectroscopy techniques, including Raman imaging, complemented by microscopic and 3D microscopic observations, we unveil new insights into the adaptive strategies of gypsum-inhabiting algae. Our Raman imaging results provide a detailed chemical map of photoprotective and photosynthetic pigments associated with microbial colonization. This map reveals a significant gradient in pigment composition, highlighting a critical survival mechanism for algae and cyanobacteria in this polyextreme environment. Intriguingly, we detected carotenoid signals not only in the algae-colonized layer but also deeper within the gypsum matrix, indicating pigment migration following cell disruption. In addition, we conducted an in-depth analysis of individual algal cells from the Trebouxiae family, noting their color variations from green to orange and describing the spectral differences in detail. This investigation identified in-vivo pigments (carotenoids, chlorophyll) and lipids at the cellular level, offering a comprehensive view of the molecular adaptations enabling life in one of Earth's most extreme habitats.