Figure 5
From: Exopolysaccharide microchannels direct bacterial motility and organize multicellular behavior
Tracking cell movement within branch structures. To observe the movement of cells within branch structures, M. xanthus cultures were added to agarose-coated microscope slides, incubated at 32 °C for 6 h to allow branch formation to occur and imaged with time-lapse fluorescence microscopy. Each series of images was captured at the swarm edge, specifically centered on branch tips when possible. Shown are merged differential interference contrast (DIC) microscopy and GFP channel images of 50:1 mixtures of each unlabeled strain with a constitutive GFP-labeled strain at times t=0 (left panels) and t=20 min (center panels). (a) M. xanthus wild-type cells, (b) epsZ-, (c) cglB- and (d) EPS overproducing pilT-. Branch structures are maintained over time in (a) wild type and (c) cglB-, whereas (b) epsZ- is unable to maintain branch organization despite cell movement and (d) pilT- shows aggregates of cells but no branch formation. Analysis of cell movement (right panels) is shown for six cells under each condition with average cell velocity indicated (in μm min−1). Parallel cell trajectories were observed only with wild type and cglB-. Scale bar represents 5 μm. (e) The average area of deviation between the observed path of a cell and its overall trajectory was determined to quantify the ability of labeled cells to maintain a consistent direction over time. P-value thresholds for statistical significance are shown as P⩽0.01:***, 0.01⩽P⩽0.05:**.
