Study of Ren, RexA, and RexB Functions Provides Insight into the Complex Interaction between Bacteriophage λ and Its Host, Escherichia coli

Abstract

The phage λ rexA and rexB genes are expressed from the PRM promoter in λ lysogens along with the cI repressor gene. RexB is also expressed from a second promoter, PLIT, embedded in rexA. The combined expression of rexA and rexB causes Escherichia coli to be more ultraviolet (UV) sensitive. Sensitivity is further increased when RexB levels are reduced by a defect in the PLIT promoter, thus the degree of sensitivity can be modulated by the ratio of RexA/RexB. Expression of the phage λ ren gene rescues this host UV sensitive phenotype; Ren also rescues an aberrant lysis phenotype caused by RexA and RexB. We screened an E. coli two-hybrid library to identify bacterial proteins with which each of these phage proteins physically interact. The results extend previous observations concerning λ Rex exclusion and show the importance of E. coli electron transport and sulfur assimilation pathways for the phage.