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Convergent evolution of pathogenicity islands in helper cos phage interference
Nuria Carpena1, Keith A Manning2, Terje Dokland2
1Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK Departamento de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad CEU Cardenal Herrera, 46113 Moncada, Valencia, Spain.
Summary
Staphylococcus aureus pathogenicity islands (SaPIs) interfere with cos-type phages by producing small capsids. This convergent evolution strategy, mediated by the SaPI-encoded ccm gene, ensures SaPI replication by blocking helper phage production.
Area of Science:
- Microbiology
- Molecular Biology
- Virology
Background:
- Staphylococcus aureus pathogenicity islands (SaPIs) are mobile genetic elements that hijack helper phage machinery for replication.
- SaPIs employ diverse strategies to interfere with helper phage reproduction, ensuring their own propagation.
- While interference with pac-type phages is understood, the mechanism for cos-type phages remained unclear.
Purpose of the Study:
- To elucidate the mechanism by which SaPIs interfere with the life cycle of cos-type helper phages.
- To identify the specific SaPI-encoded factors responsible for this interference.
Main Methods:
- Genetic analysis of SaPI-encoded genes.
- Characterization of SaPI-induced capsid production.
- Comparative analysis of SaPI-encoded proteins (Ccm vs. CpmAB).
Main Results:
- Identified the SaPI-encoded ccm gene as crucial for interfering with cos phage reproduction.
- Demonstrated that Ccm directs the production of small, isometric SaPI capsids, distinct from prolate helper phage capsids.
- Showed that Ccm and CpmAB proteins, involved in similar strategies for different phage types, share no sequence homology, indicating convergent evolution.
Conclusions:
- SaPIs utilize the SaPI-encoded ccm gene to produce small capsids, effectively blocking cos-type helper phage replication.
- The convergent evolution of capsid production mechanisms highlights a conserved strategy for SaPI propagation across different helper phage types.
- This finding deepens the understanding of SaPI-phage interactions and mobile genetic element evolution.
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