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Bacteriophage-triggered defense systems: phage adaptation and design improvements
G M Djordjevic1, T R Klaenhammer
1Department of Microbiology, North Carolina State University, Raleigh 27695-7624, USA.
Applied and Environmental Microbiology
|November 15, 1997
Summary
Bacteriophage adaptation was studied using a novel inducible suicide gene defense system. Phage mutants evolved to evade the defense, revealing a specific genetic alteration in a transcriptional activator, impacting promoter activation and defense system effectiveness.
Area of Science:
- Microbiology
- Bacteriophage Biology
- Genetic Engineering
Background:
- Bacteriophage defense systems are crucial for controlling bacterial populations.
- Inducible suicide gene systems offer a targeted approach to phage control.
- Understanding phage adaptation is key to developing robust defense strategies.
Purpose of the Study:
- To investigate phage adaptation against a novel inducible suicide gene defense system.
- To identify genetic modifications in bacteriophages that confer resistance.
- To assess the effectiveness of combining different abortive defense systems.
Main Methods:
- Challenging a Lactococcus lactis strain with a novel suicide gene system and bacteriophage phi 31.
- Selecting for resistant phage mutants through repeated transfers.
- Analyzing phage sensitivity, promoter activity (using lacZ reporter), and sequencing of the promoter region.
- Evaluating combined abortive defense systems (phi 31p-LlaIR+, Per31, AbiA).
Main Results:
- Phage phi 31 adapted, developing resistance to the suicide system.
- Mutant phages exhibited altered phi 31p promoter activation due to a specific mutation (C-to-A transversion) in the ORF2 transcriptional activator.
- The efficiency of plaquing (EOP) increased significantly for mutant phages.
- Combining defense systems drastically reduced phage EOP and population levels.
Conclusions:
- Bacteriophages can adapt to inducible suicide gene systems through specific genetic mutations.
- Targeting transcriptional activators is a viable mechanism for phage adaptation.
- Combining multiple abortive defense systems enhances phage control efficacy.