In this study, we demonstrate that the adsorption of mineral-forming cations onto a bacterial surface can lead to enhanced mineral solubilities, and we present a thermodynamic approach for quantitatively modelling this bacterial effect. We measured the dissolution of CuO in abiotic systems and in systems that contained non-metabolic whole cells of the gram-positive bacterial species Bacillus subtilis. We measured Cu concentrations, both in solution and adsorbed onto the bacteria, and we also measured dissolved organic carbon content to deconvolve the role of cell lysis on mineral dissolution. In the bacteria-bearing systems, we observed greatly elevated extents of mineral dissolution relative to the abiotic controls, caused by high concentrations of Cu adsorbed onto the cell walls. Our results indicate that bacterial cell wall adsorption can significantly lower mineral saturation states in geologic systems, causing both an increase in the extent of mineral dissolution as well as an inhibition of secondary mineral formation.