Identification and biological characteristics of a Bacillus strain antagonistic against pathogenic Aeromonas hydrophila of sturgeons

A good Bacillus strain G1 antagonistic against pathogenic Aeromonas hydrophila of sturgeons was isolated and screened from the sediment of aquaculture ponds,which produced the inhibition zone of 18.50 mm in diameter against A.hydrophila strain S1.Strain G1(GenBank accession number: HM245965.1) was identified as Bacillus amyloliquefaciens through APICH50 bacterial identification system and 16S rRNA sequence analysis.Its 16S rRNA sequence had homology of 99%-100% with those of Bacillus sp.strains submitted to GenBank,and showed the most close relative to Bacillus amyloliquefaciens strain Ba-74501(GenBank accession number: DQ422953.1).The best growth pH and temperature of strain G1 were 7 and 30 °C,its growth curve in the condition of 30 °C and 200 r/min was as follows: the lag phase was 0-6 h,the log phase was 6-54 h,the stationary phase was 54-90 h,the decline phase was after 90 h.In addition,strain G1 also exhibited good antagonistic activity against other tested A.hydrophila strains.The experimental results were conductive to fill in the data gaps about the taxonomic position of antagonists against A.hydrophila,and provide scientific data to the biocontrol on sturgeon aeromonasis.