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Bacteriophages (phages) are the most diverse and abundant life-form on Earth. Jumbophages are phages with double-stranded DNA genomes longer than 200 kbp. Among these, some jumbophages with uracil in place of thymine as a nucleic acid base, which we have tentatively termed "dU jumbophages" in this study, have been reported. Because the dU jumbophages are considered to be a living fossil from the RNA world, the evolutionary traits of dU jumbophages are of interest. In this study, we examined the phylogeny of dU jumbophages. First, tBLASTx analysis of newly sequenced dU jumbophages such as Bacillus phage PBS1 and previously isolated Staphylococcus phage S6 showed similarity to the other dU jumbophages. Second, we detected the two partial genome sequences of uncultured phages possibly relevant to dU jumbophages, scaffold_002 and scaffold_007, from wastewater metagenomics. Third, according to the gene-sharing network analysis, the dU jumbophages, including phages PBS1 and S6, and uncultured phage scaffold_002 formed a cluster, which suggested a new viral subfamily/family. Finally, analyses of the phylogenetic relationship with other phages showed that the dU jumbophage cluster, which had two clades of phages infecting Gram-negative and Gram-positive bacteria, diverged from the single ancestral phage. These findings together with previous reports may imply that dU jumbophages evolved from the same origin before divergence of Gram-negative and Gram-positive bacteria., (Copyright © 2022. Published by Elsevier B.V.)

To introduce phage therapy against multidrug-resistant Staphylococcus aureus in Western medicine, the establishment of phage manufacturing, particularly phage propagation, is indispensable. For the propagation of S. aureus phages, knowledge of the effects of phage types, process parameters, and analytical methodologies should be investigated. In this study, S. aureus phage propagations were studied in a flask with a new class of design of experiments, definitive screening design, using S. aureus phages S13' and S25-3 in different taxonomies. Four process parameters, namely, multiplicity of infection, bacterial density at infection, time of harvest, and temperature, were evaluated with the regression models based on the phage concentration data measured using plaque assay and quantitative polymerase chain reaction. As a result, phage propagations measured using plaque assay and quantitative polymerase chain reaction were overall similar to each other in the case of phage S13', while they differed in the case of phage S25-3. These results suggest that the propagation processes need to be developed according to phage type, and the choice of methodologies for phage concentration measurements should be carefully considered., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Pseudomonas aeruginosa phages belonging to the family Podoviridae are one of the well-characterized phage groups. In this study, a novel P. aeruginosa phage, KPP25, was isolated and characterized. Phage KPP25's morphology was indicative of the family Podoviridae; however, analyses of the whole genome and the virion proteins suggested that it did not belong to any of the known podophage genera. Based on these analyses, phage KPP25 appears to be a novel podophage infecting P. aeruginosa., (Copyright © 2014 Elsevier B.V. All rights reserved.)