Screening, Identification and Antimicrobial Stability of Antagonistic Bacterium FX17 against Fungus Saprolegnia parasitica
WANG Xu1,2, FENG Chunming3, SUN Shuhao3, LUO Yongcheng1,2
1. College of Agriculture, Eastern Liaoning University, Dandong 118003, China; 2. Institute of Coastal Biotechnology, Eastern Liaoning University, Dandong 118003, China; 3. Dandong Fishery Development Service Center, Dandong 118000, China
Abstract：The parasitic aquatic mold (Saprolegnia parasitica) was isolated from diseased fish tissues such as mirror common carp Cyprinus carpio var. specularis and their eggs cultured in freshwater ponds in Donggang City, Liaoning Province, through the flat panel confrontation method and the fermentation broth bacteriostasis test. Twenty-one strains of actinomycetes were isolated from soil samples around freshwater ponds in the area above, and an antagonistic strain FX17 with significant inhibition on water mildew was screened and identified by morphological characteristics and phylogenetic analysis of 16S rRNA gene sequence. The results showed that the antagonistic FX17 had average width of bacteriostatic zone of (25.40±0.13) mm, and the fermentation broth bacteriostasis rate of 73.20%, showing significant inhibitory effect on water mold. The subculture showed that the strain FX17 had a close relationship with Streptomyces tristinicus, without significant change in the inhibition rate after 10 passages (P>0.05), and without significant difference in antimicrobial activity of FX17 fermentation broth treated with different temperatures (P>0.05), indicating that the active components of its antagonistic substances were not protein metabolites. The bacteriostatic activity of antagonistic fermentation broth was shown to be varied with change in pH value significantly (P<0.05), with the maximal bacteriostatic rate of antagonistic fermentation broth in the pH range of 6.0—8.0. The findings showed that S. triostinicus FX17 had potential value to develop into a biocontrol bacterial strain against water mildew.
2020, Vol. 39 
