Unravelling bacteriophage ϕ11 requirements for packaging and transfer of mobile genetic elements in Staphylococcus aureus

Abstract

SummaryBacteriophages play a major role in spreading mobile genetic elements (MGEs)-encoded genes among bacterial populations. In spite of this, the molecular requirements for building phage transducing particles have not been completely deciphered. Here, we systematically inactivated each ORF from the packaging and lysis modules of the staphylococcal phage ϕ11, used as a model for the Siphoviridae phages infecting Gram-positive bacteria, and determined their functional role in transferring different MGEs including plasmids, staphylococcal pathogenicity islands (SaPIs) and the phage itself. In a previous report, we identified seven of these ORFs as being required for the production of functional phage or SaPI particles. In this report, we have completed the mutational analysis and have identified and characterized 15 additional phage-encoded proteins required for the production of mature phage, SaPI, or transducing particles. Apart from these, we have not yet ascertained any specific function for the six remaining ϕ11 genes, though they are highly conserved among the staphylococcal bacteriophages. To the best of our knowledge, this study represents the first systematic deletion analysis of all the ORFs comprising the morphogenetic and lysis modules of a phage, clearly defining the molecular requirements involved in phage-mediated MGEs transfer.

Staphylococcal pathogenicity island DNA packaging system involving cos -site packaging and phage-encoded HNH endonucleases

“…This was expected because SaPIbov5 lacks the SaPI packaging module and is packaged in full-sized phage particles (see below). As previously demonstrated (7,8), deletion of ϕ11 terS eliminated the packaging of phage DNA but had no effect on SaPIbov1 transfer (Table 1). This mutation, however, eliminated SaPIbov5 transfer ( Table 1), suggesting that SaPIbov5 contains a pac site that is identical or very similar to that of ϕ11 and explaining the ability of SaPIbov5 Significance Staphylococcal pathogenicity islands (SaPIs) are highly mobile and carry and disseminate superantigen and other virulence genes.…”

Fitness Costs of Plasmids: a Limit to Plasmid Transmission

“…Plasmids can be transmitted by any of the three HGT mechanisms: transformation (29,30), phage-mediated transduction (31), and conjugation (3). Conjugation is considered the most important mechanism of plasmid transmission, and the conjugative process has been extensively studied (discussed below).…”

Bacteriophage-mediated spread of bacterial virulence genes

“…Pre-emptive packaging is aided by a uniquely SaPI-coded protein, Ppi, which binds to phage TerSf and specifically blocks phage DNA packaging but not SaPI genome packaging [35 ]. In addition, SaPIs also block phage reproduction by redirecting phage capsid proteins to produce SaPI-specific particles that are too small for the larger phage genomes [42,43 ], or by expressing SaPI2 ORF17 homologs to affect the activity of the phageencoded LtrC protein [44 ] and block the expression of the phage late operon [45 ]. All these strategies not only make SaPI transfer extremely efficient, both intra-generically and inter-generically [33,34], but also interfere Phage-mediated gene transfer Penadé s et al 175 with the reproduction of infecting phages, enhancing the survival of the SaPI-positive organism [35 ].…”