Isolation,Identification And Biology Of A Lactobacillus Virulent Phage

The pollution of virulent phages may slow the fermentation, even failure, and then cause huge economic loss. So, it is considered as one of the major risk in food fermentation industry. Lactobacillus virulent P1 was isolated from the abnormal fermentation liquid of Lactobacillus plantarum IMAU10120, its characterization, resistance, adsorption, whole genome sequence, and inactivation conditions were evaluated. The results showed that this phage belonged to B1 type of Siphoviridae family. Its latent period was 45 min, burst time was 90 min. Burst size was 132.88±2.37 PFU per infective cell. Eighteen strains of Lactobacillus plantarum was infected by phage P1, two of them were relatively sensitive, five strains were sensitive, which expressed a high specificity.There was no significant influence of pH value (2.0-11.0) on its growth, but it did influence the survivability of phage P1 (P<0.05). When pH value reached to 2.0, the survival rate of phage P1 was 0. However, it can maintain more than 95% when pH value between 6.0 and 10.0. Difference temperature influenced significantly on the growth of host strain. It can grow between 30℃ and 50℃, and was inhibited at 0℃-20℃. However, there is no significant influence of temperature on the survivability of phage P1 It can sustain more 95% for all the temperatures tested.Different pH value showed significantly effects on phage P1 adsorption (P<0.05). It showed a high adsorption ability at pH 4.0-8.0 (more than 90%), and reached to the highest value at pH 7.0(more than 96%). The adsorption ability was decreased along with the increasing of pH value, and reduced to 8.33% at pH 11.0. Temperature expressed little influnce on the adsorption. Except 50℃, all the temperature tested showed a good adsorption ability. Moreover, the adsorption ability of phage P1 was influenced significantly by divalent cations, can calcium ion can significantly increased its adsorption capacities (P>0.05). Chloramphenicol expressed no effect on the phage adsorption.The inactivation effect of alcohol on phage P1 was influenced by the concentration and time.100% alcohol can obtain the best inactivation effect immediately, which can decrease 4.7 log. Taking inactivation effects and cost,50% alcohol can be considered as the best choice, which can decrease 4.2 log.100% isopropyl alcohol can decrease 5 log, which was better than 100% alcohol. Using 800ppm sodium hypochlorite treated it for 60 min, can kill all the phages. Moreover, peracetic acid can’t inactivate the phages immediately, using 0.45% peracetic acid treated for 60 min, can kill 3 logs phages.The results above can enrice the sources of Lactobacillus phage, and provide some data and theory support for explaining related infective mechanism, breeding anti-phage strains, establish related anti-phage system, and then decreasing economic loss.