Bacteria with defective rho factors suppress the effects ofN mutations in bacteriophage λ

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Abstract
A prediction based on the model forN-gene function of bacteriophage λ proposed by Roberts (1971) is confirmed by showing that a λN − double mutant is able to grow in strains ofE. coli with defective rho transcription termination factors. The burst sizes for λN − in these strains range from 5 to 24% the burst sizes for λN + in the same strain. This low level of suppression is also evident in the levels of synthesis of the λ exonuclease and is consistent with other evidence that the defect in the rho factors of these strains is only partial. These strains do not suppress the effects of mutations in genesO, P andQ of λ nor in genes30 and43 of bacteriophage T4. The lack of suppression of λQ − is significant because theQ-gene product, like theN-gene product, is believed to function as an anti-terminator of λ transcription but at termination sites that may not require rho factor action.