Characterization and genome analysis of two novel Aeromonas hydrophila phages PZL-Ah1and PZL-Ah8
Aeromonas hydrophila (A.hydrophila) is an opportunistic pathogen of fish-human-livestock, which poses a seriously affects to the development of aquaculture. Phage therapy is considered as a process to alternatively control bacterial infections and contaminations. In this study, the genomes of two Aeromonas hydrophila- specific phages PZL-Ah1 and PZL-Ah8 were isolated, characterized and genomic sequence analyzed. Transmission electron microscopy showed that the two phages had been classified as
... he member of the Podoviridae family. Both the two phages in this study had relatively narrow host range with lytic activity against Aeromonas spp. strains. However, they could lyse 3 common A.hydrophila strain. As revealed from the whole genomic sequence analysis, PZL-Ah1 and PZL-Ah8 coverd the double-stranded genome of 38,641 bp and 40,855 bp in length, with the GC content of 53.68% and 51.89%, respectively. Through gene comparison in NCBI database revealed that PZL-Ah1 and PZL-Ah8 were 97.67% − 95.51% identical to Stenotrophomonas phage IME15 and Aeromonas Phage T7-Ah. Phylogenetic analysis showed that PZL-Ah8, PZL-Ah1 and other two phages belonged to the same genus. A total of 44 and 52 open reading frames (ORFs) were predicted in the PZL-Ah1 and PZL-Ah8 genome, respectively. In the process of gene annotation, 28 (63.6%) ORFs in PZL-Ah1 and 29 (55.8%) ORFs in PZL-Ah8 were known to functional proteins in NCBI database, while the remaining ORFs were classified as "hypothetical proteins", whose functions were yet unknown. By comparing, ORF 02, ORF 29 and ORF 04 in PZL-Ah1, ORF24 in PZL-Ah8 were responsible for the host cell lysis. In conclusion, genomic studies of these two novel phages would lay the foundation for expanding the phage genome database and providing good candidates for phage typing applications.