Experimental vs. Natural Mineral Precipitation in Modern Microbialites: The Case Study of the Alkaline Bagno Dell’acqua Lake (Pantelleria Island, Italy)

Microbial activity has been documented in various lacustrine environments suggesting its fun-damental role on minerals precipitation and, therefore, on the formation of organo-deposits such as microbialites. Many studies are currently focused on documenting how the association of mi-crobes and extracellular polymeric substance (EPS) may influence the authigenesis of Mg-rich clay minerals and the subsequent carbonate precipitation in growing microbialites in lacustrine en-vironments. In this study we investigate the present-day microbialites of the alkaline Bagno dell’Acqua lake (Pantelleria Island, Italy) using X-ray diffraction (XRD) scanning electron mi-croscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Our results reveal the intimate association of Mg-smectite/carbonate minerals with EPS and microbes and, for the first time, we selected microbes belonging to phylum Firmicutes (Bacillus sp.), from natural microbialites to carry out laboratory experiments that testify their direct role on the precipitation of clay and carbonate minerals.