Characterization of Novel Erwinia amylovora Jumbo Bacteriophages from Eneladusvirus Genus

Abstract

Jumbo phages, which have a genome size of more than 200 kb, have recently been reported for the first time. However, limited information is available regarding their characteristics because few jumbo phages have been isolated. Therefore, in this study, we aimed to isolate and characterize other jumbo phages. We performed comparative genomic analysis of three Erwinia phages (pEa_SNUABM_12, pEa_SNUABM_47, and pEa_SNUABM_50), each of which had a genome size of approximately 360 kb (32.5% GC content). These phages were predicted to harbor 546, 540, and 540 open reading frames with 32, 34, and 35 tRNAs, respectively. Almost all of the genes in these phages could not be functionally annotated but showed high sequence similarity with genes encoded in Serratia phage BF, a member of Eneladusvirus. The detailed comparative and phylogenetic analyses presented in this study contribute to our understanding of the diversity and evolution of Erwinia phage and the genus Eneladusvirus.

The Bacteriophage pEp_SNUABM_08 Is a Novel Singleton Siphovirus with High Host Specificity for Erwinia pyrifoliae

“…Phage isolation was performed as described previously, with minor modifications [ 23 ]. To isolate E.-pyrifoliae -infecting phages, 48 samples (31 water samples and 17 soil samples) were obtained from an area located near the region where the blight outbreak was reported in South Korea.…”

“…Samples positive for lysis zones or plaque(s) were collected to confirm their plaque-forming capacity. The samples were centrifuged, syringe-filtered (0.45 μm), and subjected to a conventional double-layer agar (DLA) assay [ 23 ]. The plaques were subcultured five times to obtain a single phage lysate.…”

“…Phage propagation and purification were performed using the DLA assay in accordance with a previously described protocol with minor modifications [ 23 ]. The 18 h cultured top agar was collected using SM buffer (100 mM NaCl, 50 mM Tris (pH 7.5), and 10 mM MgSO 4 ) and centrifuged to isolate phages from the agar matrix, after which it was filtered through a 0.45 μm membrane filter.…”

“…A total of 55 strains including Erwinia spp. (26 E. amylovora strains and 25 E. pyrifoliae strains) isolated from the blight-affected plant tissue were examined for host range analysis using the spot method [ 23 ]. The presence of inhibition zone or plaque(s) on the spotted area was considered to denote susceptibility; infectivity was represented as + and − for susceptible and nonsusceptible cases, respectively.…”

“…A number of phages that infect Erwinia have been characterized and sequenced thus far. However, the majority of these phages target E. amylovora , and limited information is available on phages that infect E. pyrifoliae [ 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. Moreover, the majority of Erwinia phages that have been studied belong to the family Myoviridae [ 30 ].…”