title: Genomic characterization provides new insight into Salmonella phage diversity.
abstract: BACKGROUND
  Salmonella is a widely distributed foodborne pathogen that causes tens of millions of salmonellosis cases globally every year. While the genomic diversity of Salmonella is increasingly well studied, our knowledge of Salmonella phage genomic diversity is still rather limited, despite the contributions of both lysogenic and lytic phages to Salmonella virulence, diversity and ecology (e.g., through horizontal gene transfer and Salmonella lysis). To gain a better understanding of phage diversity in a specific ecological niche, we sequenced 22 Salmonella phages isolated from a number of dairy farms from New York State (United States) and analyzed them using a comparative genomics approach.
  
  
  RESULTS
  Classification of the 22 phages according to the presence/absence of orthologous genes allowed for classification into 8 well supported clusters. In addition to two phage clusters that represent novel virulent Salmonella phages, we also identified four phage clusters that each contained previously characterized phages from multiple continents. Our analyses also identified two clusters of phages that carry putative virulence (e.g., adhesins) and antimicrobial resistance (tellurite and bicyclomycin) genes as well as virulent and temperate transducing phages. Insights into phage evolution from our analyses include (i) identification of DNA metabolism genes that may facilitate nucleotide synthesis in phages with a G+C % distinct from Salmonella, and (ii) evidence of Salmonella phage tailspike and fiber diversity due to both single nucleotide polymorphisms and major re-arrangements, which may affect the host specificity of Salmonella phages.
  
  
  CONCLUSIONS
  Genomics-based characterization of 22 Salmonella phages isolated from dairy farms allowed for identification of a number of novel Salmonella phages. While the comparative genomics analyses of these phages provide a number of new insights in the evolution and diversity of Salmonella phages, they only represent a first glimpse into the diversity of Salmonella phages that is likely to be discovered when phages from different environments are characterized.
authors.affiliation: Department of Food Science, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Andrea I
authors.initials: AI
authors.lastname: Moreno Switt
authors.forename: Renato H
authors.initials: RH
authors.lastname: Orsi
authors.forename: Henk C
authors.initials: HC
authors.lastname: den Bakker
authors.forename: Kitiya
authors.initials: K
authors.lastname: Vongkamjan
authors.forename: Craig
authors.initials: C
authors.lastname: Altier
authors.forename: Martin
authors.initials: M
authors.lastname: Wiedmann
mesh_terms: D000595:Amino Acid Sequence; D000890:Anti-Infective Agents / Q000494:pharmacology; D001435:Bacteriophages / Q000187:drug effects / Q000235:genetics* / Q000472:pathogenicity; D016000:Cluster Analysis; D004279:DNA, Viral / Q000378:metabolism; D024882:Drug Resistance, Viral / Q000235:genetics; D004777:Environment; D014644:Genetic Variation; D023281:Genomics; D008969:Molecular Sequence Data; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D012475:Salmonella / Q000821:virology*; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics
chemical_list: D000890:Anti-Infective Agents; D004279:DNA, Viral; D014764:Viral Proteins