The drops were allowed to dry and then the
plates were overlaid with 3 ml of 0.7% (w/v) agar seeded with
100 μl of a suspension of Bacillus spp. cells with an OD600
of 0.3, prepared from a 24 h culture. After 24 h incubation
at 30 °C, inhibition of growth of the strain was expressed
in arbitrary units (AU) of activity per ml. One AU was the
amount of the active fraction of the CFCS in 10 μl of the highest
dilution which completely inhibited the growth of the test strain
in the agar covering a drop. Experiments were performed in
triplicate.