The Presence of Both Phage PS8 and Agrobacterium turnefaciens A6 DNA Base Sequences in A6‐Induced Sterile Crown‐Gall Tissue Cultured in vitro

Abstract

The presence of both Agrobacterium tumefaciens and phage PS8 DNA base sequences in sterile crown‐gall tissue grown in vitro was demonstrated by hybridization experiments using crown gall DNA and [3H]RNAs complementary to the bacteria and phage DNAs. These experiments were done under stringent conditions minimizing mismatching of the bases. The approximate amount of A. tumefaciens DNA and PS8 DNA base sequences in crown gall DNA was respectively 9 and 900 genome equivalents. Data are presented indicating that the A6 genome equivalents consist of many copies of a small part of the bacterial genome, while the PS8 genomes are present almost completely. The A6 segment must be large enough to code for four proteins specific for A. tumefaciens present in the crown gall cells and also form a fractional part of the PS8 genome. In cells of the A6 strain used in the experiments no prophage is integrated in the genome of the bacteria. It is postulated that PS8–like DNA is present as a plasmid. Further hybridization‐competition experiments using [3H]cRNA from A. radiobacter showed that one‐third of the A. tumefaciens DNA base sequences in crown gall are also present in A. rudiobacter DNA.No plaque‐forming activity was observed when crown gall tissue homogenates were tested.