| Caulobacter crescentus, a non-pathogenic, freshwater bacterium, has an adhesive holdfast that has been identified as nature's strongest glue. An enhanced understanding of the physical and chemical properties of the holdfast may facilitate its implementation as a novel bioadhesive. The environmental factors that influence how motile swarmer cells transform into adhered stalked cells and generate holdfasts are analyzed. Additionally, methods to isolate motile cells from a heterogeneous cell culture are developed for these adhesion investigations. Microfluidic devices offer several advantages over traditional biological assays that include the ability to quantify single-cell adhesion events and to sort and monitor specific subpopulations of bacteria. In an initial study, microfluidic devices enable the testing of a variety of surfaces to investigate the holdfast-surface interactions of C. crescentus. Altering the dimensions, surface topography, and chemical composition of the microchannels can promote or impede the production of permanent holdfasts. Fluorescence microscopy is used to differentiate between bacteria that are reversibly and permanently adhered to the surface. These microchannel-based adhesion studies illustrate that C. crescentus prefers to adhere to more hydrophobic substrates. In a second study, proper combination of microchannel geometry and applied hydrostatic pressures permits the separation of motile from non-motile bacteria by taking advantage of the motile cells ability to swim away from a hydrostatically focused stream of cells. |
