Abstract: Bacteriophage infection usually occurs in industrial fermentation,thus this work aims to isolate and screen bacteriophage with Bacillus subtilis as host,to analyze its biological characteristics,and to screen anti-phage strains via spontaneous mutation. With B. subtilis KC-260 as the host bacterium,a bacteriophage,designated as P260,was isolated and purified from the fermentation broth. Its titer was measured after enrichment culture,and then its biological characteristics such as thermal stability,optimal multiplicity of infection,host range,inhibitor,disinfectant-tolerance,etc. were investigated. In order to prevent the contamination from phage P260,anti-phage 260 strains were screened by spontaneous mutations. As results,titer of P260 reached 3.45×10¹⁰ PFU/mL,it had a certain host specificity,and not sensitive to Bacillus coagulans and Bacillus pumilus. P260 easily lost its activity at high temperature,i.e.,not heat-resistant,and its survival rate under 70℃ condition for 15 min decreased significantly. ClO₂ in 25 mg/L had a strong exterminate effect on P260. The 0.5% ammonium oxalate and ammonium citrate presented inhibition to P260. Optimal multiplicity of infection of phage P260 to the host was 0.01,one step growth curve showed that the incubation period was 15 min and the lytic stage started after 45 min. An anti-phage strain ZF-260 was obtained by spontaneous mutation. ZF-260 was not affected when adding phage P260,which indicated that ZF-260 was an excellent strain of anti-phage P260. In conclusion,the biological characteristics of phage P260 was studied,and ZF-260 with stable genetic and high viable cell count was obtained.

Key words: Bacillus subtilis, bacteriophages, inhibitor, disinfectant, spontaneous mutation