Figure 1.

The human pathogen S. aureus forms biofilm streamers. (a) Schematic drawing of the experimental apparatus, where the flow through the channel (cross section of 200 μm × 200 μm) was driven by a syringe pump, which was set to a flow rate of 1.5 ± 0.05 μL/min. (b) S. aureus biofilms were visualized with a green fluorescent nucleic acid stain (SYTO 9, Invitrogen), and a confocal microscope was used to obtain three-dimensional images of S. aureus agr group I (strain RN6734). The suspension we flowed through the channel was at a cell density that corresponds to OD₆₀₀=1.2. The edges of the microfluidic channel are indicated with purple lines. The inset illustrates that the biofilm streamer is a porous filamentous structure. The diameter of the streamer network is ∼100 μm in this image. The image in the inset was taken with the focal plane perpendicular to the vertical z-axis, and in the middle of the channel, which is 100 μm from the bottom of the channel. The scale bar represents 200 μm.