Bacteriophages of Staphylococcus aureus efficiently package various bacterial genes and mobile genetic elements including SCCmec with different frequencies

Abstract

Staphylococcus aureus is a serious human and veterinary pathogen in which new strains with increasing virulence and antimicrobial resistance occur due to acquiring new genes by horizontal transfer. It is generally accepted that temperate bacteriophages play a major role in gene transfer. In this study, we proved the presence of various bacterial genes of the S. aureus COL strain directly within the phage particles via qPCR and quantified their packaging frequency. Non-parametric statistical analysis showed that transducing bacteriophages φ11, φ80 and φ80α of serogroup B, in contrast to serogroup A bacteriophage φ81, efficiently package selected chromosomal genes localized in 4 various loci of the chromosome and 8 genes carried on variable elements, such as staphylococcal cassette chromosome SCCmec, staphylococcal pathogenicity island SaPI1, genomic islands vSaα and vSaβ, and plasmids with various frequency. Bacterial gene copy number per ng of DNA isolated from phage particles ranged between 1.05 × 10(2) for the tetK plasmid gene and 3.86 × 10(5) for the SaPI1 integrase gene. The new and crucial finding that serogroup B bacteriophages can package concurrently ccrA1 (1.16 × 10(4)) and mecA (1.26 × 10(4)) located at SCCmec type I into their capsids indicates that generalized transduction plays an important role in the evolution and emergence of new methicillin-resistant clones.

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Ecological and Evolutionary Benefits of Temperate Phage: What Does or Doesn't Kill You Makes You Stronger

“…[14] Phages employing the "headful" DNA packaging mechanism for example have very high rates of transduction [15,16] while it is uncommon in others. [17] For the transducing phage there can be serious costs, particularly if some or all of the phage's own genome is excluded from the virus capsid. [18] There can also be biases in the DNA that is transferred, since in some cases other mobile genetic elements such as pathogenicity islands are disproportionately mobilized by transduction relative to the genome as a whole.…”

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