FIG. 1.

(a) Time-series optical micrograph in transmission mode from the microchannel center at (i) 29 h, (ii) 30 h, (iii) 31 h, and (iv) 32 h after inoculation. Dark portions show high optical density biofilm features. Yellow and green arrows highlight the displacement of visible segments in time. Scale bar is 700 μm. (b) Biofilm after 55 h with background subtraction using the t = 46 h frame. Differences between images at 55 h and 46 h are shown, with sudden partial detachment events coloured in red and continuous biofilm motion coloured in black. Scale bar is 1 mm. Flow is from left to right in (a) and (b). (c) A simplified schematic for the proposed streamer formation by partial detachment. A shear force applied to a biofilm segment (grey) by a liquid flow (blue arrow) causes a small biofilm portion to become partially detached, leaving behind a void (cross-hatched). The partially detached biofilm segment (red) rotates to align itself in the direction of the liquid flow, becoming a streamer.