Kappa, a bacterial endosymbiont present in killer stocks of Paramecium aurelia, exists in two forms - brights, which contain a refractile (R) body, and non-brights which lack the R body. Non-brights are self-reproducing and give rise to brights, which cannot reproduce and are toxic to sensitive paramecia which ingest them. Associated with the R body are structures resembling bacteriophages in form and chemical composition. Animals of stock 51, syngen 4 of P. aurelia were given low doses of ultraviolet light. The percentage of brights increased markedly, beginning 6 h after irradiation. In three experiments, absolute numbers of kappas were determined 13 to 14 h after exposure to u.v.: the number of brights increased and non-brights decreased significantly, while the total number of kappas remained the same. At 24 h, after irradiation the numbers of kappa particles had decreased considerably; after 3 days they were completely gone. The results are consistent with the hypothesis that the phage-like structures exist as u.v.-inducible prophages in non-brights, and that when a non-bright becomes a bright, the prophage is spontaneously induced forming, at the same time, mature phage-like elements and the R body. These events constitute the lytic cycle which ends with the destruction of the bright.
GrimesG. W., PreerJ. R.Jun1971; Further observations on the correlation between kappa and phage-like particles in paramecium. Genetical Research 18:115–116
JurandA., RudmanB. M., PreerJ. R.Jun1971; Prelethal effects of killing action BY stock 7 of Paramecium aurelia. Journal of Experimental Zoology 177:365–387
MuellerJ. A.1963; Separation of kappa particles with infective activity from those with killing activity and identification of the infective particles in Paramecium aurelia. Experimental Cell Research 30:492–508
PreerJ. R.JunPreerL. B.1967; Virus-like bodies in killer paramecia. Proceedings of the National Academy of Sciences of the United States of America 58:1774–1781
PreerJ. R.JunPreerL. B., RudmanB., JurandA.1971; Isolation and composition of bacteriophage-like particles from kappa of killer paramecia. Molecular and General Genetics 111:202–208
PreerJ. R.JunSiegelR. W., StarkP. S.1953; The relationship between kappa and paramecia in Paramecium aurelia. Proceedings of the National Academy of Sciences of the United States of America 39:1228–1233
SonnebornT. M.1943; Gene and cytoplasm. I. The determination and inheritance of the killer character in variety 4 of P. aurelia. II. The bearing of determination and inheritance of characters in P. aurelia on problems of cytoplasmic inheritance, pneumococcus transformations, mutations and development. Proceedings of the National Academy of Sciences of the United States of America 29:329–343