The role of microbial extracellular polymeric substances on formation of sulfate minerals and fibrous Mg-clays

A variety of Mg-, Na- and Ca-sulfates, including gypsum, Mg-clays precipitate within the microbial mats that developed seasonally in hypersaline playa lake El Longar (Central Spain). multidisciplinary study along a transect demonstrates degree lithification increases from soft poorly lithified layers lying on submerged ground to highly crystalline present desiccated fringes. The community composition is diverse, dominated terms OTUs by Proteobacteria, Firmicutes Cyanobacteria. Proteobacteria include sulfur-cycling microbes, supporting biogeochemical cycling this element. Cyanobacteria are dominant EPS producers have both been shown play role turnover. Several ions (e.g., Mg, S, Si, Al, Fe, Ca, Na) bound functional groups EPS. abundance sulfate carboxylic acids suggested strong binding capacity for Mg2+ Ca2+, which were higher mats. Na, K, SO42− Si more concentrated matrices than natural brines. concentration sufficient mixture minerals through freeze-drying, similar found intact In types minerals, sulfates Mg-clays, exposed areas. These results suggest mineral nucleation occurred during degradation when was progressively likely released high amounts ions. helps understand intrasedimentary growth clays presence these assemblage can be related potential biosignature past life Earth possibly also exoplanets, like Mars.