9502872 Koh This project is designed to further develop, and test the diffusion gradient system constructed during Phase I research. The system consists of a diffusion gradient chamber (DGC) for culturing microorganisms in multiple, continuous diffusion gradients of small soluble molecules. In addition, there is an effluent chamber for consolidating effluent flow from the DGCs, a transilluminator that provides back lighting to visualize microbial growth, and a camera system to monitor and quantify microbial growth and movement. This phase of the research will focus on refining and reducing the cost of the system, and demonstrating its versatility for studying a variety of problems in microbial and cellular biology. The feasibility of constructing the DGC by injection molding will be investigated. This would improve its quality and reduce its cost. An automated tracking camera system will be designed and tested that will enhance the quantitative power of the system. A temperature control unit that encloses the entire system and maintains a stable temperature will be tested. The system s capability to establish gradients will be tested in collaboration with Michigan State University (MSU). A number of solutes will be tested in the DGC and the empirical results will be compared with results predicted by a mathematical model Scientist at MSU will also evaluate the system s ability to track population changes in a detoxifying bacterial community exposed to multiple gradients, and they will study the role of chemotaxis in competition between defined mixed cultures of bacteria. In addition, they will use the DGC to elucidate patterns of gene expression in response to environmental stimulus using reporter genes in Rhizobium meliloti. A University of Michigan scientist will also study the growth and response of a tissue culture line of osteoblast cells to imposed gradients in the DGC.
