Chemical heterogeneity of proton and metal complexation by bacterial cell and bacteriogenic iron oxide surfaces.
Published: 2004
Language: eng
Number of pages: 172
Description: This study focuses on the detailed characterization of proton and metal reactivity on the surface of bacterial cells. Studies concerning proton and metal cation binding to reactive cell surfaces were designed to assess surface chemical heterogeneity through the development of new or custom modified chemical equilibrium models. The linear programming model (LPM) was used to assess metal sorption on intact Escherichia coli (Gram-) and  Bacillus subtilis (Gram+) cells. This method was also used for the study of metal cation interactions in the presence of bacteriogenic iron oxides (BIOS). In the first instance, the validity of LPM was determined from comparison of its efficiency with that of other models such as FITEQL. Proton affinity to intact bacterial cells, mentioned a priori, and BIOS were assessed using a f&barbelow;ully o&barbelow;ptimized c&barbelow;ontinuo us pKa affinity spectral model (FOCUS). Results from the LPM analysis of intact bacterial cells showed that there are at least three metal cation reactive sites on the surfaces of Gram+ and Gram- cells. This is consistent with recently reported spectroscopic studies and validates the use of LPM to the study of complex geochemically reactive solids. The BIOS are composed of a highly porous matrix of ferrihydrite with embedded intact and fragmented bacterial cells. Analysis of this material using LPM suggested the presence of an average of three metal binding sites on the BIOS surface as well as on its organic (bacteria) fraction. LPM methods disclosed the non-additive nature of the BIOS, along with the similarity of its surface reactivity with that of pure iron oxyhydroxide surfaces. Intact bacterial cells were investigated using a combination of empirical and electrostatic models. FOCUS and a Donnan shell model were used to calculate apparent and intrinsic acidity constants on the Gram+ and Gram- surfaces as a function of varying ionic strength. These models found minimal difference between apparent and intrinsic acidity constant values, suggesting little effect of ionic strength variations on the proton affinity of surface functional groups. FOCUS was then employed to investigate the proton binding characteristics of the BIOS. This analysis revealed a striking similarity between the reactivity of the BIOS and that of pure iron oxide phases such as goethite and lepidocrocite. This indicates an extensive masking of underlying organic functional groups by ferrihydrite, which emphasizes the non-additive nature of the BIOS.
Notes: Adviser: F. Grant Ferris.

Thesis (Ph.D.)--University of Toronto, 2004.

Electronic version licensed for access by U. of T. users.

Source: Dissertation Abstracts International, Volume: 65-05, Section: B, page: 2301.