Adhesion of individual bacteria to surfaces is the first step in biofilm formation, which increases the antibiotic resistance of the bacteria. Our lab is using the bacterium Caulobacter crescentus as a model to study the initial steps of the adhesion process. C. crescentus displays a dimorphic lifecycle and exhibits a transition from the motile swarmer stage to the sessile stalked stage either developmentally or after contacting a surface. During adhesion stimulated by surface contact, a swarmer cell strikes the surface, adheres, sheds its flagellum, synthesizes an adhesive holdfast, and develops a stalk. Holdfast formation is triggered by cellular development typically occurs after 20-30 min, whereas holdfast formation in response to surface contact is considerably faster (e.g., 20-30 s). To study bacterial adhesion, we are using three-layer microfluidic devices with integrated pumps and valves that combine automated cell culture, synchronization, and analysis. To better understand the role of the flagellum in surface contact stimulated holdfast formation, we compared adhesion of wild-type cells and flagellum motor mutant cells (?motB). Synchronized populations are transferred to an analysis channel where reversible and irreversible adhesion events are monitored by fluorescence microscopy. To observe holdfast formation on-chip, a fluorescently labeled lectin that attaches to the holdfast is added to the medium. Over a 50-min experiment, holdfast formation times by surface contact processes and cellular development are easily determined.

Microfluidic devices to track adhesion of single cells to surfaces

246th National Meeting (2013)

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