Paper BI-ThP23
Patterning Live Bacterial Cells for Biological Applications

Thursday, October 18, 2007, 5:30 pm, Room 4C

The immobilization of live bacterial cells in a controlled fashion in well-defined patterns will have many applications in biosensors, and in biomedical and fundamental biological studies. The surface antigens, fimbriae and flagella of Salmonella typhimurium and Escherichia coli and corresponding antibodies were used to demonstrate the immobilization of live bacteria in well-defined patterns. The leashing of live bacterial cells was achieved on antibody-modified substrates of gold, silicon and glass. The tendency of bacterial cells to remain adhered (leashed) only to the antibody-modified areas was used to fabricate microarray patterns whose size can be controlled down to a micron scale. Patterns are generated with either a focused ion beam milling system or a microplotter. Cells patterned in this way retain their viability for at least six hours in a PBS buffer solution and are capable of regeneration if incubated in a growth medium. These microarray patterns can serve as prototype sensors which are able to capture targeted pathogens including bacteria, virus and proteins. For example, we have already demonstrated the use of such microarrays as a bacterial sorting system, in which a pre-targeted bacterial strain is captured and isolated from a mixed culture of microorganisms. The technique offers a reliable approach for fundamental microbiological research on the behavior of bacteria in an immobilized mode, as microorganisms respond to environ¬mental changes. For example, we observed that individual S. typhimurium cells gradually adjust their orientation from a "lying down" to a "standing up" position during regeneration, presumably trying to leave their position in search of more food. In such a struggle, immobilized cells produce a larger number of flagella as compared with planktonic cells, as confirmed by SEM and AFM studies.