Characterization and genomic analysis of a novel Pseudoalteromonas phage PS_L5.

Pseudoalteromonas is a widely distributed bacterial genus that is associated with marine algae. However, there is still limited knowledge about their bacteriophage. In this study, we reported the isolation of a novel lytic bacteriophage that infects Pseudoalteromonas marina. Transmission electron microscopy revealed that PS_L5 had an icosahedral head of 52.6 ± 2 nm and a non-contractile tail with length of 96.5 ± 2 nm. The genome sequence of this phage was 34, 257 bp and had a GC content of 40.75%. Furthermore, this genome contained 61 predicted open reading frames (ORFs), which involved in various functions such as phage structure, packaging, DNA metabolism, host lysis and other additional functions. Additionally, the phylogenetic analysis based on major capsid protein showed that the phage PS_L5 was closely related to five other Pseudoalteromonas phages, namely PHS3, PHS21, AL, SL25 and Pq0 which also possessed the non-contractile long tail. This study provided the fundamental insights into the evolutionary dynamics of Pseudoalteromonas phages and the interaction between phage and host.

Isolation and genome sequencing of a novel lytic Pseudoalteromonas phage SL20.

Phage SL20, a novel lytic Pseudoalteromonas phage, was isolated from the coastal waters of the Yellow Sea, China. The microbiological characterization demonstrated that phage SL20 was relatively stable from 35 to 55 °C and the optimal pH was approximately 6.0. A latent period of approximately 24 min was indicated by a one-step growth curve. The burst size was approximately 12 ± 3 PFU/cell. The genome had a length of 120,295 bp with a G + C content of 35.84%, and predicted 95 ORFs. The phylogenetic tree based on DNA helicase showed that Pseudoalteromonas phage SL20 was related to the Pseudoalteromonas phage H101 and was a member of the family Shandongvirus. The isolation and genomic analysis of SL20 has improved our understanding of host-phage interactions and the ecology of the marine bacteria Pseudoalteromonas.