Time resolved mineralization of calcium carbonate in medium with and without Zn2+. The initial stages of the mineral formation show no differences between the cultures in media with and without Zn2+ and various Ca-acetate concentrations. A) After 24 h bacteria show no sign of accumulation of inorganic particles on the cell surface. B) and C) In the further course of the cultivation (7 days), bacteria accumulate globular inorganic particles in different amounts on the cell surface. Bars represent 1 μm.