Biological Characteristics And Inactivation Methods Of Lysogenic Bacillus Phage

Bacillus is used in various food industries for its unique probiotic characteristics,however,some Bacillus strains contain lysogenic phage.These phage can easily become virulent via external factors such as ultraviolet light or mitomycin.Lysis of the host by phage not only affects their growth but also contributes to significant economic losses.In this study,a strain of Bacillus licheniformis was induced by ultraviolet and mitomycin.A virulent phage was subsequently induced and its morphological and biological characteristics were investigated.In addition,the influence of environmental factors on its tolerance and adsorption capacity,as well as its resistance to temperature and chemical reagents were studied.The results are as follows:(1)The optimal condition for lysogenic phage induction was radiation for 10 s at 10-15 cm from an ultraviolet lamp(254nm,wavelength)in nutrient medium.The phage was identified as belonging to the Myoviridae family.The optimal multiplicity of infection of this phage was 10,the incubation period was 45 min,and then entered the lytic phase,which entered a stationary phase at 105 min.Its average burst size was 104.48±2.70 PFU.(2)B1 phage was completely inactivated at pH 2 and 3.The survival level at 0?,was c 19.4%.Maximum survival(c.90.2%)of phage was achieved at 36 C.(3)pH exhibited little effect on the adsorption level of B1 phage.Adsorption rates levels were all greater than 90%at pH from 5.0 to 9.0.The adsorption capacity or level of the phage was stable at temperatures from 0 to 36?,reaching up to 90%.Adsorption of the phage decreased slightly to c.85%at 50?.The addition of divalent ions or chloramphenicol did not significantly(P<0.05)affect its adsorption capacity.(4)At 63?,RSM medium can provide a better protect effect to phage B1.72?treated for 10min can inactivate the phages totally.(5)In addition to peroxyacetic acid,the inactivation effects of ethanol and isopropanol on phage B1 were positively correlated with reagent concentration and treatment time;75%ethanol or 50%isopropanol could completely inactivate the bacteriophage B1 within 15 minutes.