Carotenoid-enriched endolithic phototrophic communities in Colombian gypsums

Gypsum has been shown to serve both as a protective shield against intense solar irradiation and as a microhabitat for microbial life, particularly under extreme environmental conditions. This study presents the first report of endolithic photosynthetic microbial communities and their associated protective pigments in gypsum deposits from Los Santos (Santander, ~ 400–800 m a.s.l.), Sáchica (Boyacá, ~ 2200 m a.s.l.), and Chaparral (Tolima, ~ 400–700 m a.s.l.). We investigated phototrophic biodiversity within gypsum with a focus on the photoprotective adaptation mechanisms mediated by carotenoid pigments, employing a multi-analytical approach. Raman and FT-MIR spectroscopy revealed distinct spectral signatures corresponding to β-carotene, lycopene, astaxanthin as well as potential signals of canthaxanthin, and lutein in red, yellow, black, and green pigmented zones. These results were complemented by microbiological culturing and scanning electron microscopy (SEM), which confirmed the presence of Cladophora sp., Coccomyxa sp., and Chlorella sp. (green algae), as well as Phormidium sp. (cyanobacteria), arranged as long filaments or isolated cells embedded within the gypsum matrix. These findings expand our understanding of microbial biodiversity in equatorial evaporitic environments and highlight the role of gypsum as an optical refuge that filters harmful UV radiation while transmitting photosynthetically active wavelengths. Furthermore, this study provides valuable astrobiological insights and proposes a complementary methodological framework for future missions targeting Martian gypsum deposits, which may represent protective niches for potential microbial life or preserved biosignatures from past or present life.