a, Sedimentation phenotype of S. mutans strains after overnight growth in THY broth. b, Sedimentation phenotype of sacculi purified from S. mutans strains. Sacculi were resuspended in PBS (OD600 of 8), and allowed to sediment for 72 hours at 4 °C. c, DIC images of S. mutans strains taken from mid-log growth phase. Blue arrows denote small round cells. Scale bar is 1 μm. Representative images from at least three independent experiments are shown in a, b and c.