Interfacial complexation modeling of manganese and zinc adsorption to viable Shewanella putrefaciens CN32

The fate of metals in soils is of great interest both in terms of nutrient acquisition and contaminant containment. The present work investigates the protolytic response of a dissimilatory metal reducing bacterium Shewanella putrefaciens CN32 to changing environmental pH across three ionic strengths. Determining the coefficients of protolytic response and metal adsorption is confounded by structural complexity. The non-ideal competitive adsorption (NICA) model was applied to titration data to account for the structural heterogeneity. CN32 shed protons from two proton reactive groups as pH increased. The cells exhibit log10KH values for the two sites of 6.13 (+/- 0.11) and 8.12 (+/- 0.14) with total site densities of 25.6 (+/- 1.68) mmol/kg and 23.3 (+/- 1.69) mmol/kg respectively. The concentration of net positive charge was determined as 27.4 (+/- 0.65) mmol/kg. After exposure to individual treatments of 0.1 mmol Mn and Zn, cells developed a net negative shift in whole cell charge.