Typically, the effects of ionic strength on metal adsorption to geosorbents are accounted for by models of the surface electric field, assuming a planar surface. However, bacterial cell walls are not two-dimensional surfaces. Furthermore, electric field model parameters for complex systems are difficult to determine and apply. We propose an alternative approach to electric field models of ionic strength effects by explicitly accounting for monovalent cation adsorption onto specific bacterial binding sites. We calculate stability constants for monovalent metal-bacterial surface complexes, and use them to determine the magnitude of correction needed for a previously determined stability constant for a Cd-bacterial surface complex.