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Beyond the chromosome: the prevalence of unique extra-chromosomal bacteriophages with integrated virulence genes in

Bryan Utter1, Douglas R Deutsch1, Raymond Schuch1

  • 1Laboratory of Bacterial Pathogenesis and Immunology, The Rockefeller University, New York, New York, United States of America.

Plos One
|June 26, 2014
PubMed

Insights

Extra-chromosomal prophages (ExPΦs) are widespread in Staphylococcus aureus, impacting virulence and antibiotic resistance. This study reveals a new layer of genetic diversity in these stealth elements, crucial for pathogenesis.

Area of Science:

  • Microbiology
  • Genomics
  • Bacteriophage Research

Background:

  • The role of chromosomally integrated prophages in Staphylococcus aureus virulence is established.
  • The existence and impact of extra-chromosomal prophages (plasmidial and episomal) in S. aureus remain largely unknown.
  • Previous genomic studies have overlooked extra-chromosomal genetic elements.

Purpose of the Study:

  • To investigate the prevalence and characteristics of extra-chromosomal prophages (ExPΦs) in Staphylococcus aureus.
  • To identify potential virulence factors and antibiotic resistance genes associated with these elements.
  • To understand the contribution of ExPΦs to bacterial pathogenesis and strain diversity.

Main Methods:

  • Selective enrichment and sequencing of extra-chromosomal DNA from S. aureus isolates using Roche-454 technology.
  • Complete genome sequencing and annotation of a representative extra-chromosomal prophage (ФBU01).
  • Bioinformatic analysis to identify virulence determinants, antibiotic resistance genes, and mobile genetic elements.

Main Results:

  • Widespread distribution of multiple ExPΦs was discovered in both antibiotic-sensitive and -resistant S. aureus strains.
  • A 43.8 kbp circular ExPΦ (ФBU01) was fully sequenced, revealing putative virulence factors within a bacteriophage immune evasion cluster (IEC).
  • Numerous potential virulence factors and antibiotic resistance genes were identified on various ExPΦs and other mobile genetic elements.

Conclusions:

  • Extra-chromosomal prophages represent a significant, previously unrecognized source of genetic diversity in Staphylococcus aureus.
  • These stealth elements likely play a crucial role in S. aureus pathogenesis and adaptation.
  • Horizontal gene transfer involving ExPΦs contributes to strain diversity and the spread of virulence and resistance traits.

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