The rex genes of bacteriophage lambda can inhibit cell function without phage superinfection

Area of Science:

• Molecular Biology
• Virology
• Genetics

Background:

• Bacteriophage lambda RexA and RexB proteins are known to mediate the exclusion of superinfecting phages.
• The precise mechanism by which Rex proteins exert exclusion is not fully understood.

Purpose of the Study:

• To investigate the phenotypes associated with the overexpression of bacteriophage lambda rexA and rexB genes.
• To elucidate the role of RexA and RexB protein ratios in phage exclusion.

Main Methods:

• Cloning of rexA and rexB genes into a multicopy plasmid.
• Overexpression of genes using the inducible tac promoter.
• Phenotypic analysis of bacterial cells under different gene expression conditions.

Main Results:

• Overexpression of both rexA and rexB, or rexA alone, did not cause significant phenotypes.
• Induction of rexA in the presence of limiting rexB activity led to immediate cessation of cell growth.
• Macromolecular synthesis and amino acid transport were inhibited, and intracellular ATP levels dropped.

Conclusions:

• The ratio of RexA to RexB proteins is critical for regulating cell growth.
• The observed phenotypes mimic those of phage superinfection, supporting a model where altered Rex protein ratios contribute to exclusion.