Isolation and Preliminary Characterization of Cryptic Plasmids from Erwinia carotovora

Of the fifty-two Erwinia carotovorastrains studied, sixteen were found to contain extrachromosomal DNA (plasmids) from 2.5 to 129 kbp in size. Some E. carotovorastrains bore two to five different plasmids. Experiments showed that the cryptic plasmids of erwinia are not responsible for their resistance to antibiotics and are not involved in the synthesis of macromolecular colicin-like carotovoricins. At the same time, one of the E. carotovorastrains, 13A, augmented the production of carotovoricin after curing from one of its plasmids, the 47.7-kbp pCA 6-2. Three E. carotovorasubsp.carotovorastrains and one E. carotovorasubsp.atrosepticastrain contained large 129-kbp plasmids, which may play a role in the ecology of phytopathogenic pectinolytic erwinia.