Figure 4. Visualizing autoaggregation as sedimentation.

Autoaggregation in liquid media mediated by (A) the heat-resistant agglutinin 1 gene expressed in Escherichia coli from an arabinose inducible promoter on the pBAD vector after induction with arabinose (B) vector control prepared with the same protocol. The tubes show settling patterns in broth cultures left statically for 6 h and the photomicrographs are crystal violet stained mounts of cells taken from just above the pellet. (C) Autoaggregation chain-forming Streptococcus salivarius in semi-lquid media. Chain-forming streptococci produce spherical suspended colonies (black arrow) while mutants unable to form chains produce ‘roots’ in the semi-solid medium (red arrow). Reproduced from Couvigny et al. 2018 [31] under a Creative Commons Attribution License.