Bacteria and their products have the ability to adsorb metals and can have a great impact on the global cycling of these metals. Detailed information about the quantity and reactivity of different components in the system is important to develop geochemical models that can predict the fate of these metals. This dissertation presents the work of three studies that provide critical insights into metal-bacterial adsorption reactions. Chapter 2 describes the adsorption and subsequent reduction of

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... (III) both Grampositive and Gram-negative bacteria, as well as reactions with bacterial exudates. The experimental results reveal that the speciation of the aqueous Au and the bacterial surface controls the rate of Au removal; under low pH conditions aqueous Au complexes adsorb readily and rapidly. With increasing pH, adsorption slows significantly. Bacterial exudates can reduce Au(III) at circumneutral pH, but on a slower time scale than the bacterial cell wall. Chapter 3 focuses on the extracellular polysaccharides (EPS) produced by bacteria and whether EPS is important in proton and Cd binding, relative to the cell wall. Our results suggest that EPS contains functional groups that are similar to those on the cell wall, and that EPS and bacterial cell walls exhibit similar site concentrations and affinities for adsorbing protons and metal cations from solution. In