Biological Characteristics And Comparative Genomics Analysis Of Cold-active Phage VSW-3 Infecting Pseudomonas Fluorescents

Phage is the most abundant form of life on Earth,and is the most diverse natural gene pool.More and more studies have shown that phages play important roles in environmental food web processes,biogeochemical cycles,gene transfer,structure and diversity of prokaryotes.In this study,the cold-active phage VSW-3,isolated from the Napahai Plateau wetland water samples,infecting the Pseudomonas fluorescens VSW-3 was chose as the experimental material.The biology characteristics,whole genome sequencing and analysis,and comparative genomics analysis of phage VSW-3 were carried out.First,the biological characteristics of phage VSW-3 were studied.Transmission electron microscopy showed that VSW-3 belong to Podoviridae.It was typical cold-active phages which could infect and lyse the host cell at 4?;the optimal infection pH of VSW-3 was 7.0,the MOI was 1.0;latency and lysis period were 40 min and 60 min;It was not sensitive to chloroform,but very sensitive to Triton X-100 and SDS.Genomic restriction endonuclease map and SDS-PAGE analysis of capsid protein showed that the genome sizes was about 40 Kb,and major capsid protein was about 38 KDa.Genomic analysis of VSW-3 revealed that the genome sizes was 40,556 bp,and G+C content was 57.4%.The genome length was similar to the other P.fluorescens phage genomes that have been sequenced.Phage VSW-3 contained 46 genes encoding proteins,and it had its own DNA primer enzyme,helicase,DNA polymerase and RNA polymerase.Comparative genomics analysis showed that VSW-3 had a significant linear relationship with Pseudomonas phage Bf7 and Phi-2.It can be seen 146 Pseudomonas phage species into five groups based on the phylogenetic trees.P.fluorescens phage VSW-3 was associated with 73 and vB Pass-Kakhheti25 in a branch,and the phylogenetic relationship was close to YMC11/07/P54 PAE BP.COG function noted that phage VSW-3 was not much functional genes,but contained some genes associated with replication transcriptional modifications.In this study,the biology characteristics,whole genome sequencing and analysis of phage VSW-3 were carried out,and gene structure and function were predicted theoretically.It will provid theoretical basis for the study on the interaction between phage and host bacteria.