The SL-biofilm in Additional file 5: Movie 4 had formed
after a liquid culture of H. volcanii H53 cells that had been
freshly diluted in Hv-YPC medium (to OD 600 nm= 0.25)
was transferred to Petri dishes and left to incubate for
5 days. Social motility as accessed by rapid formation
of cellular extensions was induced in these biofilms by
tapping the lid of the Petri dish, or by gently lifting and
re-lowering the Petri dish approximately 1 cm. Such
agitation did not disturb the overall biofilm; however,
it caused smaller defects in loose biofilm structures,
which were followed by prolonged social motility