For probiotic bacillus screening, after inhibitory effect of fish gastrointestinal tracts bacilli
against F. columnare KJ720207 were performed in order to select the best strain of probiotic
bacillus for the identification. Phenotypic characteristics and 16S rDNA sequencing method were
used for this probiotic bacillus characterization at the species level and the selected strain was
found to be B. amyloliquefaciens KJ720206 which was showed 100% homology with the strain YH-
22 from the GenBank database. Normally, bacilli are transient bacteria, the strain KJ720206 from
fish gut might be come from surrounding water or soil. This study was in agreement with that of
Coa et al. (2011) who reported that B. amyloliquefaciens isolate G1 from the brackish water
sediment samples displayed a significant in vitro inhibitory effect against the eel-pathogenic