title: F factor-mediated immunity to lethal zygosis in Escherichia coli K-12.
abstract: Recipient (F(-)) cells of Escherichia coli are sensitive to an excess of Hfr donor cells. This phenomenon of lethal zygosis is associated with conjugation and is observed as a continuous fall in F(-) viable cells during liquid mating, or as inhibition of F(-) growth on solid media. One class of survivors, which arose in the zones of inhibition on solid media, was no longer sensitive to lethal zygosis and exhibited the following properties: sensitivity to male-specific phage, donor ability, and surface exclusion. Since these characteristics were sensitive to acridine orange treatment, the strains carry an F factor extrachromosomally. They are, however, defective in some way since they retain sensitivity to female-specific phage. Temporary sensitivity to lethal zygosis in these and in standard F(+) strains can be induced by the formation of F(-) phenocopies. We have suggested that there is an immunity to lethal zygosis (Ilz(+)) associated with the F factor and discuss the results in terms of this hypothesis.
mesh_terms: D000166:Acridines / Q000494:pharmacology; D002470:Cell Survival; D003090:Coliphages; D003227:Conjugation, Genetic; D003433:Crosses, Genetic; D003470:Culture Media; D004269:DNA, Bacterial; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development*; D005111:Extrachromosomal Inheritance; D008242:Lysogeny; D009154:Mutation; D011995:Recombination, Genetic
chemical_list: D000166:Acridines; D003470:Culture Media; D004269:DNA, Bacterial