Production of biogenic Mn oxides by Leprothrix discophora SS-1 in a chemically defined growth medium and evaluation of their Pb adsorption characteristics

Biogenic Mn oxides were produced by the bacterium Leptothrix discophora SS- 1 (= ATCC 3182) in a chemically defined mineral salts medium, and the Pb bi nding and specific surface area of these oxides were characterized. Growth of SS-I in the defined medium with pyruvate as a carbon and energy source r equired the addition of vitamin B-12. Complete oxidation of Mn(II) within 6 0 h required the addition of greater than or equal to 0.1 mu M FeSO4. Pb ad sorption isotherms were determined for the biogenic Mn oxides (and associat ed cells with their extracellular polymer) and compared to the Pb adsorptio n isotherms of cells and exopolymer alone, as well as to abiotic Mn oxides. The Pb adsorption to cells and exopolymer with biogenic Mn oxides (0.8 mmo l of Mn per g) at pH 6.0 and 25 degrees C was 2 orders of magnitude greater than the Pb adsorption to cells and exopolymer alone (on a dry weight basi s). The Pb adsorption to the biogenic Mn oxide was two to five times greate r than the Pb adsorption to a chemically precipitated abiotic Mn oxide and several orders of magnitude greater than the Pb adsorption to two commercia lly available crystalline MnO2 minerals, The N-2 Brunauer-Emmet-Teller spec ific surface areas of the biogenic Mn oxide and fresh Mn oxide precipitate (224 and 58 m(2)/g, respectively) were significantly greater than those of the commercial Mn oxide minerals (0.048 and 4.7 m(2)/g). The Pb adsorption capacity of the biogenic Mn oxide also exceeded that of a chemically precip itated colloidal hydrous Fe oxide under similar solution conditions. These results show that amorphous biogenic Mn oxides similar to those produced by SS-1 may play a significant role in the control of trace metal phase distr ibution in aquatic systems.