Microbial Attachment to Minerals: Experimental Studies on Mineral-Driven Chemotaxis, & Role of Crystallography & Microtopography in Site-Specific, Oriented Cell Attachmen

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In order to assess and predict the impact microorganisms have on processes such as mineral dissolution and precipitation over a wide range of environments, we need first information on where cells occur. It is well known that microbial biomass in the environment is highly heterogeneous, and that cells are generally found attached to surfaces rather than free living. Yet what controls cell distribution - in effect what surfaces they attach to - is poorly understood. Microbial attachment to surfaces has been widely studied but rarely in context that can be used to understand to natural systems. Studies to date have largely been based on simplified models that neglect certain factors that may be key in determining the natural distribution of cells.The proposed research focuses on determining the microbial mechanisms and surface forces that govern microbial attachment to mineral surfaces. Specific goals include: 1) determining the importance of microbial metabolism in determining substrate specificity for attachment, and 2) determining what role crystal chemistry, crystal structure, and surface microtopography (steric effects) play in attachment. To achieve these goals, two primary lines of experiments will be conducted. To determine the role of microbial metabolism, attachment assays will be conducted with microorganisms selected for specific metabolic capabilities, with the aim of quantitatively determining the role chemotaxis plays in substrate selectivity. To determine how steric effects impact attachment, experiments will be conducted in concert with theoretical calculations that account for factors such as cell type, cell wall thickness, cell size, etc. Specific surface forces between microbial cells and mineral substrata will be quantified by Atomic Force Microscopy (AFM).