Study of Ren, RexA, and RexB Functions Provides Insight Into the Complex Interaction Between Bacteriophage λ and Its Host, .

The phage λ and genes are expressed from the promoter in λ lysogens along with the I repressor gene. is also expressed from a second promoter, , embedded in . The combined expression of and causes to be more ultraviolet (UV) sensitive. Sensitivity is further increased when RexB levels are reduced by a defect in the promoter, thus the degree of sensitivity can be modulated by the ratio of RexA/RexB. Expression of the phage λ gene rescues this host UV sensitive phenotype; Ren also rescues an aberrant lysis phenotype caused by RexA and RexB. We screened an 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 electron transport and sulfur assimilation pathways for the phage.