Inactivation And Genomic Analysis Of Lactobacillus Plantarum Virulent Bacteriophage P2

Lactobacillus is one of the most important bacteria used in the fermentation production of dairy products and the widespread prevalence of target bacteriophage has created great economical loss to the dairy industry.Therefore,protocols to inactivate bacteriophage have become a more and more important problem in dairy industry.Inactivation of phage using a combination of methods including culture method,biocides and heat treatment are now being investigated as possible intervention strategies.In this respect the effect of various culture media:reconstituted skim milk,Tris magnesium gelatin buffer.and deMan Rogosa Sharpe broth,temperature(63,72,90℃),and biocides(ethanol,isopropanol,sodium hypochlorite and peroxyacetic acid)were evaluated as possible virucidal agents using Lactobacillus plantarum virulent phage P2.In all cases efficacy was evaluated following treatment for 1 hour.The results of the study indicated that the phage P2 could be totally inactivated in 10 min at 90℃ and in 40 min at 72℃.Moreover,reconstituted skim milk and MRS provided the best and least protection,respectively.With the exception of peracetic acid,the inactivation effects of the remaining biocides increased with increasing concentration.Treatment with ethanol(100%)resulted in a 4.31 log reduction.Absolute isopropanol resulted in a 5.98 log reduction,which was better than that of absolute ethanol.With sodium hypochlorite,800 and 400 ppm treatment for 30 and 50 min,respectively resulted in total inactivation of phage P2.Peracetic acid,regardless of concentration,exhibited no significant effect on the survival of phage P2.Sodium hypochlorite was the only biocide evaluated which resulted in complete inactivation of phageIn addition,the genomic structure of Lactobacillus plantarum virulent bacteriophage P2 was sequenced by Illumina Hiseq 4000.The results showed that the genome was a linear with a length of 78 kb and an average GC content of 39.3%.It encoded 96 CDS,and 2 tRNA.The homology between phage P2 and P1 using the same host strain was 99%as indicated by comparative genomic analysis.Comparative genomic analysis with Lactobacillus plantarum phage B2 indicated that the homology in tail protein synthesis(tail protein g18,tail tape measure g25 and tail fiber protein g28)was low and that these proteins were associated with the inactivation effects of sodium hypochlorite.Moreover,homology related with capsid protein synthesis(capsid protein gl6,major capsid protein g17.minor structural protein g 26,minor structural protein g27)was low indicating that these proteins may influence the inactivation effects of alcohol and peroxyacetic acid.The homology of DNA replication module was high.However,some hypothetical proteins showed low similarity,this may be caused by genetic evolution of Lactobacillus plantarum when adapting to its environment.This area of research requires more investigation.