Biosaline formations (BSFs) are complex self-organized biomineral patterns formed by ‘‘hibernating’’ bacteria
as the biofilm that contains them dries out. They were initially described in drying biofilms of Escherichia coli
cells + NaCl. Due to their intricate 3-D morphology and anhydrobiosis, these biomineralogical structures are of
great interest in astrobiology. Here we report experimental data obtained with various alkali halide salts (NaF,
NaCl, NaBr, LiCl, KCl, CsCl) on BSF formation with E. coli and Bacillus subtilis bacteria at two saline
concentrations: 9 and 18 mg/mL. Our results indicate that, except for LiCl, which is inactive, all the salts
assayed are active during BSF formation and capable of promoting the generation of distinctive drying patterns
at each salt concentration. Remarkably, the BSFs produced by these two bacterial species produce characteristic
architectural hallmarks as the BSF dries. The potential biogenicity of these biosaline drying patterns is studied,
and the astrobiological implications of these findings are discussed
