Polynucleotide sequence relationships among Ent plasmids and the relationship between Ent and other plasmids.

Deoxyribonucleic acid-deoxyribonucleic acid hybridization studies reveal that the plasmids coding for the production of heat stable and heat labile enteroxtoxins of Escherichia coli, regardless of their origin, have a majority of their polynucleotide sequences in common, but are not related in any significant way to those plasmids coding for the synthesis of only ST toxin. The heat stable and heat labile plasmids also share a significant degree of their polynucleotide sequences with plasmids of the FI and FII incompatibility groups, but not with R factors belonging to the I, N, W, P, or X incompatibility groups.