Dissertation
Roles of Temperature and Ionic Strengths of Growth in Bacterial Surface Biopolymer Properties, DLVO and Specific Interactions Governing the Bioadhesion of L. monocytogenes to Silicon Nitride
Doctor of Philosophy (PhD), Washington State University
01/2012
Handle:
https://hdl.handle.net/2376/4274
Abstract
The effects of the surface biopolymers' properties of L. monocytogenes EGDe on the electrostatic, Liftshitz-van der Waals and steric interactions to a model surface of silicon nitride AFM tip were investigated for the bacterial cells grown at five different temperatures (10, 20, 30, 37 and 40oC) and ionic strengths (0.003, 0.05, 0.1, 0.3, and 0.5M). The higher adhesion was always associated with lower negative cell surface potential and longer surface biopolymer brushes. Transitions in the adhesion affinities, physiochemical properties and the structure of bacterial surface brushes were observed for the cells grown at 30oC and IS of 0.1M. Our results suggested that the lowest long-range electrostatic repulsion which was partially balanced by the Liftshitz-van der Waals attraction was responsible for the lowest energy barrier to adhesion as predicted by soft-particle analysis of the DLVO theory and the lower adhesion measured by AFM. For the cells grown at various temperatures, the contribution of "specific" forces to the overall adhesion force at the closest surface proximities was investigated. Adhesion forces were decoupled into specific (hydrogen bonding) and nonspecific force components using Poisson statistical analysis. The strongest specific and nonspecific attraction were observed for cells grown at 30oC, compared to those observed for cells grown at higher or lower temperatures, respectively. Our results showed that, irrespective of the temperature of growth investigated, hydrogen bonding forces were always stronger than the nonspecific forces. As the final step, we have investigated the factors that affect the molecular-scale bacterial adhesion process from a thermodynamic perspective at a fundamental level using statistical mechanics. By applying Boltzmann distribution to the probability histograms of bacterial adhesion affinities measured between the cells grown at various ionic strengths and silicon nitride by AFM, the total number of molecules involved in the adhesion process and the entropy of the bacterial surface molecules were estimated. Our results provided a thermodynamic evidence of the direct relationship between the strength of bacterial adhesion and the number of bacterial surface molecules available for interactions and the length of bacterial surface biopolymer brush.
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Details
- Title
- Roles of Temperature and Ionic Strengths of Growth in Bacterial Surface Biopolymer Properties, DLVO and Specific Interactions Governing the Bioadhesion of L. monocytogenes to Silicon Nitride
- Creators
- Fatma Pinar Gordesli
- Contributors
- NEHAL I ABULAIL (Advisor)CORNELIUS F IVORY (Committee Member)HALUK BEYENAL (Committee Member)JAMES PETERSEN (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Chemical Engineering and Bioengineering, School of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 191
- Identifiers
- 99900581453701842
- Language
- English
- Resource Type
- Dissertation