Soluble intracellular calcium concentrations in media with 0.2% (left) and 0.4% (right) Ca-acetate concentrations. The soluble intracellular calcium levels showed a dependency of the presence of zinc in the medium. Bacteria cells accumulated calcium to higher levels in medium with zinc acetate (MH 2Z and MH 4Z) compared to media without elevated zinc concentrations (MH 2 and MH 4). Concentrations of calcium are indicated in the columns in μg/mL. The concentration of calcium at day 1 was not determined (n.d.) due to cell density limitations.