Thermosensitive step associated with transfer of the Ti plasmid during conjugation: Possible relation to transformation in crown gall

It is reported here that transfer by means of a conjugative process of an oncogenic plasmid from a virulent strain of Agrobacterium tumefaciens to a strain of that organism that had been cured of the plasmid is thermosensitive. Since the thermosensitive step found in the conjugative process appears similar in every respect to a thermosensitive step that is involved in the transformation of a normal cell to a tumor cell in the crown gall disease of plants, it is suggested that the observed results may reflect the existence of a thermosensitive step that is common to these two processes