Two microliter suspensions [1–2
107 colony-forming units
(CFU)/ml] of the potential PSB were inoculated on NBRIP and
NBRIP-BPB (NBRIP media with 0.025 g/l bromophenol blue, BPB)
plates simultaneously. The ratio of the diameter of the halo (HD) to
the diameter of the colony (CD) was calculated for each strain