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Bacteriophage P22 SieA-mediated superinfection exclusion
Justin C Leavitt1, Brianna M Woodbury2, Eddie B Gilcrease3
1School of Biological Sciences, University of Utah, Salt Lake City, Utah, USA.
Mbio
|January 18, 2024
Summary
Salmonella phage P22
Area of Science:
- Bacteriophage biology
- Microbial genetics
- Molecular mechanisms of viral defense
Background:
- Temperate phages can provide bacterial hosts with defense against superinfection.
- Salmonella phage P22 possesses multiple prophage-expressed superinfection exclusion systems.
- The SieA system is one such defense mechanism encoded by P22.
Purpose of the Study:
- To elucidate the molecular mechanism of superinfection exclusion mediated by the P22 SieA protein.
- To identify the host or phage components targeted by SieA.
- To understand the evolutionary implications of SieA and its interactions.
Main Methods:
- Isolation and characterization of P22 mutants resistant to SieA-mediated exclusion.
- Analysis of amino acid changes in P22 ejection proteins (gp16 and gp20).
- Construction and testing of hybrid phages with genes from other phage types.
- Sequence analysis of different SieA protein types.
Main Results:
- The P22-encoded SieA protein is an inner membrane protein essential for exclusion.
- SieA specifically blocks DNA injection by P22 and related phages, not other tailed phages.
- Mutations in P22 genes 16 and 20 overcome SieA-mediated exclusion.
- Hybrid phages incorporating HK620 ejection protein genes show partial resistance to SieA.
- Diverse SieA variants exhibit conserved target specificity despite low sequence identity.
Conclusions:
- SieA functions by interfering with the assembly or function of the phage DNA delivery conduit (gp16 and gp20).
- This mechanism represents a novel strategy for superinfection exclusion in bacteriophages.
- The findings provide insight into the co-evolutionary arms race between bacteria and phages.
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