Tandem mobilization of anti-phage defenses alongside SCCmec elements in staphylococci

Area of Science:

• Microbiology
• Bacterial genetics
• Viral-bacterial interactions

Background:

• Bacteria possess diverse immune systems to combat viral infections (phages).
• Horizontal gene transfer mechanisms for these defense systems are poorly understood, particularly in pathogenic bacteria.
• Staphylococci are opportunistic pathogens causing significant antibiotic-resistant infections.

Purpose of the Study:

• To investigate the mechanisms of antiviral defense system spread in staphylococci.
• To explore the role of mobile genetic elements in the dissemination of bacterial immunity.

Main Methods:

• Analysis of staphylococcal genomes, focusing on SCCmec regions.
• Investigation of gene content within SCC-like cassettes.
• Experimental assessment of cassette mobilization triggered by phage infection.

Main Results:

• Staphylococci harbor anti-phage defense genes linked to SCC (staphylococcal cassette chromosome) mec cassettes.
• SCCmec-encoded recombinases facilitate the mobilization of SCCmec and adjacent SCC-like cassettes.
• Phage infection induces the excision and circularization of these cassettes, promoting their spread.

Conclusions:

• SCC/SCCmec cassettes are crucial mobile elements in staphylococci.
• These cassettes contribute to both the spread of antibiotic resistance and the horizontal transfer of anti-phage defense systems.
• Phage-mediated mobilization is a key mechanism for disseminating bacterial antiviral immunity.