Genomic structure of phage F22, a hybrid between serologically and morphologically unrelated Salmonella typhimurium bacteriophages P22 and Fels 2

Genome Analysis and Therapeutic Evaluation of a Novel Lytic Bacteriophage of Salmonella Typhimurium: Suggestive of a New Genus in the Subfamily Vequintavirinae

Salmonella Typhimurium, a foodborne pathogen, is a major concern for food safety. Its MDR serovars of animal origin pose a serious threat to the human population. Phage therapy can be an alternative for the treatment of such MDR Salmonella serovars. In this study, we report on detailed genome analyses of a novel Salmonella phage (Salmonella-Phage-SSBI34) and evaluate its therapeutic potential. The phage was evaluated for latent time, burst size, host range, and bacterial growth reduction in liquid cultures. The phage stability was examined at various pH levels and temperatures. The genome analysis (141.095 Kb) indicated that its nucleotide sequence is novel, as it exhibited only 1-7% DNA coverage. The phage genome features 44% GC content, and 234 putative open reading frames were predicted. The genome was predicted to encode for 28 structural proteins and 40 enzymes related to nucleotide metabolism, DNA modification, and protein synthesis. Further, the genome features 11 tRNA genes for 10 different amino acids, indicating alternate codon usage, and hosts a unique hydrolase for bacterial lysis. This study provides new insights into the subfamily Vequintavirinae, of which SSBI34 may represent a new genus.

Salmonella phages and prophages: genomics, taxonomy, and applied aspects

Since this book was originally published in 2007 there has been a significant increase in the number of Salmonella bacteriophages, particularly lytic virus, and Salmonella strains which have been fully sequenced. In addition, new insights into phage taxonomy have resulted in new phage genera, some of which have been recognized by the International Committee of Taxonomy of Viruses (ICTV). The properties of each of these genera are discussed, along with the role of phage as agents of genetic exchange, as therapeutic agents, and their involvement in phage typing.

Molecular characterization of the Salmonella enterica serovar Typhi Vi-typing bacteriophage E1

Some bacteriophages target potentially pathogenic bacteria by exploiting surface-associated virulence factors as receptors. For example, phage have been identified that exhibit specificity for Vi capsule producing Salmonella enterica serovar Typhi. Here we have characterized the Vi-associated E1-typing bacteriophage using a number of molecular approaches. The absolute requirement for Vi capsule expression for infectivity was demonstrated using different Vi-negative S. enterica derivatives. The phage particles were shown to have an icosahedral head and a long noncontractile tail structure. The genome is 45,362 bp in length with defined capsid and tail regions that exhibit significant homology to the S. enterica transducing phage ES18. Mass spectrometry was used to confirm the presence of a number of hypothetical proteins in the Vi phage E1 particle and demonstrate that a number of phage proteins are modified posttranslationally. The genome of the Vi phage E1 is significantly related to other bacteriophages belonging to the same serovar Typhi phage-typing set, and we demonstrate a role for phage DNA modification in determining host specificity.

Salmonella phages and prophages--genomics and practical aspects

Numerous bacteriophages specific to Salmonella have been isolated or identified as part of host genome sequencing projects. Phylogenetic analysis of the sequenced phages, based on related protein content using CoreGenes, reveals that these viruses fall into five groupings (P27-like, P2-like, lambdoid, P22-like, and T7-like) and three outliers (epsilon15, KS7, and Felix O1). The P27 group is only represented by ST64B; the P2 group contains Fels-2, SopEphi, and PSP3; the lambdoid Salmonella phages include Gifsy-1, Gifsy-2, and Fels-1. The P22-like viruses include epsilon34, ES18, P22, ST104, and ST64T. The only member of the T7-like group is SP6. The properties of each of these phages are discussed, along with their role as agents of genetic exchange and as therapeutic agents and their involvement in phage typing.