| This thesis presents the results and discussion of a multi-faceted investigation of the manganese-binding properties of bacterial exopolymers and of some ecological consequences of the interactions between bacterial exopolymers and manganese. Data are presented on the effect of culture conditions on the chemical composition and manganese-binding behavior of exopolymers produced by the freshwater and terrestrial bacteria Arthrobacter ramosus, Pedomicrobium americanum, P. ferrugineum, P. manganicum, and two Pseudomonas sp., and by the marine bacterium Deleya marina. Pedomicrobium ferrugineum, P. manganicum, and Deleya marina all changed the composition of the exopolymers they produced in response to changes in the amount of organic nutrients available and the amount of surface area present in the growth medium. The exopolymers produced by Deleya marina also changed over the course of the organisms growth cycle.; The manganese-binding characteristics of the exopolymers were measured using equilibrium dialysis and x-ray photoelectron spectroscopy (XPS). The presence of higher levels of organic nutrients in the growth medium led to the production of exopolymers by Pedomicrobium sp. and by Deleya marina with increased manganese-binding behavior as compared to exopolymers harvested from low nutrient-level cultures. The presence of large amounts of surface area in the growth medium led to the production of exopolymers by Pedomicrobium sp. and by Deleya marina with undetectable manganese-binding activity. In addition, in a low nutrient medium, Deleya marina produced exopolymers with undetectable manganese-binding during exponential growth, but exopolymers harvested from stationary phase cultures exhibited measurable manganese-binding. XPS revealed that exopolymers which bound manganese were consistently either reduced or oxidized in response to manganese. Thus, XPS has been shown to be useful as a technique for studying the chemistry of complex organic ligands.; Bacterial exopolymers were also shown to influence the mobility of manganese in soil columns and corrosion of mild steel. Manganese added to soil as part of an exopolymer/metal complex stayed in solution more than manganese added as an inorganic salt. Exopolymers from Pedomicrobium sp. passivated the corrosion of mild steel in physically undisturbed conditions. This passivation may break down when the exopolymer coated metal surface is exposed to higher shear forces. |
