In situ mapping of community-level cellular response with catalytic microbiosensors

Chemotaxis, the migration of cells in the direction of a spatial chemical g radient, is important in disease progression, microbial ecology, and biorem ediation. The ability to map chemoattractant gradients and the correspondin g cellular growth and motility patterns is essential to the study of chemot axis. Microelectrodes and microbiosensors have the potential to measure che moattractant gradients with high spatial resolution. In this study, Clark-t ype amperometric microelectrodes and microbiosensors were used to measure s olute concentrations gradients generated by a chemotactic band of Escherich ia coli in a semi-solid gel. A computerized image analysis system was used to simultaneously measure the cellular concentration profile across the che motactic band. The experimental results compared favorably with a mathemati cal model of solute and cell transport in the gel. Scanning electron microg raphs (SEM) of micro(bio)sensor tips taken after 6 months of use showed evi dence of degradation, including adhesion of foreign particles to the glass body, the adhesion of a small gel capsule to the sensor tip, and separation of the bio-interface from the tip. A needle-type microbiosensor was constr ucted to better protect the tip and hence increase the ruggedness of the mi crobiosensors. (C) 1998 Elsevier Science S.A. All rights reserved.