sapi

SaPIs (Staphylococcus aureus pathogenicity islands) are a family of ~15 kb mobile genetic elements resident in the genomes of the vast majority of S. aureus strains. Much like bacteriophages, SaPIs can be transferred to uninfected cells and integrate into the host chromosome. Unlike the bacterial viruses, however, integrated SaPIs are mobilized by host infection with "helper" bacteriophages (specific SaPIs may require specific helper bacteriophages for mobilization, though Staphylococcus phage 80alpha appears to mobilize all known SaPIs). SaPIs are used by the host bacteria to co-opt the phage reproduction cycle for their own genetic transduction and also inhibit phage reproduction in the process.SaPIs can infect many strains that are resistant to phages, and can readily be transferred to Listeria monocytogenes even though staphylococcal phages cannot grow in Listeria cells. SaPIs occur infrequently in other staphylococcal species, but SaPI-like elements are common and widespread in other Gram-positive cocci.

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