The basis of cell-to-cell transformation in Paramecium bursaria. II. Investigation into the molecular nature of the transforming agent.

A mating type transformation, involving cell-to-cell contact (abortive conjugation) insyngen 4 of Parameciwn bursaria has been investigated. By autoradiography, transfer of material between the conjugants in normal and abortive conjugation has been shown to occur. The transfer of this material, which includes protein, RNA and DNA, during abortive conjugation has been shown to be necessary if the transformation is to occur. The mating type substances produced by sexually competent cells of different mating types have been characterized with respect to their thermal stability. In all cases examined there appeared to be 3 mating type substances produced which had different temperature stabilities. No differences could be shown between the transformed cells and normal cells of the same mating type in relation to stability of mating type substance.