Bacterial mutants able to partly suppress the effect of N mutations in bacteriophage lambda

A method is described whereby bacterial mutants (sun) may be selected which are able to specifically suppress mutations in the N gene of bacteriophage lambda. The sun mutations seem to be allelic to suA mutations, which suppress the polarity of nonsense codons, since suA mutants have all of the properties of sun mutants and both are genetically linked to the ilv gene. In the light of these experiments and recent data by others, models originally suggested to explain polarity in bacterial operons, are discussed with regard to their possible relevance to the mechanism of N action.