Bacteriophage lambda repressor allelic modulation of the Rex exclusion phenotype.

Area of Science:

• Molecular Biology
• Genetics
• Virology

Background:

• Bacteriophage lambda utilizes Rex exclusion to prevent superinfection by other lambda phages.
• The bacteriophage lambda cI repressor and Rex proteins (RexA, RexB) are crucial for this exclusion mechanism.

Purpose of the Study:

• To investigate how different alleles of the bacteriophage lambda cI repressor modulate the sensitivity of specific lambda mutants to Rex exclusion.
• To identify genetic elements involved in cI repressor-mediated regulation of Rex exclusion.

Main Methods:

• Comparative plaque assays were performed using bacteriophage lambda mutants (delta red-gam delta ren) and lysogens with defined cI repressor alleles (cI+ and cI[Ts]857).
• Genetic mapping was employed to locate elements influencing Rex exclusion activity.

Main Results:

• A temperature-sensitive cI allele (cI[Ts]857) significantly increased Rex exclusion of lambda mutants compared to the wild-type cI+ allele.
• The augmentation of Rex exclusion by cI[Ts]857 was found to be recessive to cI+.
• A genetic element located outside the cI-rexA-rexB region was implicated in the enhanced Rex exclusion observed with the cI857 allele.

Conclusions:

• The bacteriophage lambda cI repressor allele plays a critical role in modulating Rex exclusion efficiency.
• The cI857 allele enhances Rex exclusion, suggesting a complex regulatory network involving factors beyond the immediate cI-rexA-rexB locus.