title: Phenotypic correction of nonsense mutation carrying non-converting PE5 phages in Shigella flexneri with suppressor gene.
abstract: (i) Phenotypic suppression by aminoglycoside antibiotics of a polyauxotrophic Shigella flexneri var. Y strain on partially completed minimal medium has shown that its Thr dependence is associated with nonsense mutation. Induced Thr+ revertants selected from the culture yielded clones correcting the lytic cycle of nonsense T4 mutant phages. Transfer of R1am plasmid to these clones carrying a nonsense mutation of ampicillin resistance was performed. In this manner a S. flexneri var. Y derivative was isolated which, on the basis of the phenotypic correction of T4 phages and R1am factor, proved to be a suppressor positive clone. (ii) From phage PE5 responsible for conversion of type antigen V, mutants were isolated that had lost their converting capacity. Selected Sup+ and control Sup- strains were treated with the mutant phages and examined for the appearance of type antigen V. Three phage mutants were found to induce antigen conversion only in Sup+ strains. (iii) The data suggest that, at least with phage PE5, the information for type antigen conversion is carried by phage genome.
mesh_terms: D000617:Aminoglycosides / Q000494:pharmacology; D000956:Antigens, Viral; D003090:Coliphages / Q000235:genetics* / Q000276:immunology; D005814:Genes, Viral; D008242:Lysogeny; D009154:Mutation; D010641:Phenotype; D011815:R Factors; D012763:Shigella flexneri / Q000235:genetics*; D013489:Suppression, Genetic; D013912:Threonine / Q000096:biosynthesis; D010948:Viral Plaque Assay
chemical_list: D000617:Aminoglycosides; D000956:Antigens, Viral; D013912:Threonine