FIG. 2.

Detection of transfer of CTX^calcφ and CTX^ETφ from supernatants of AS207 to O395 using Southern blot analysis of plasmid DNA. Undigested plasmid DNAs were run on agarose gels, transferred to a nylon membrane, and sequentially hybridized with probes for rstR^calc (left panel) and rstR^ET (right panel). Plasmid DNA was prepared from O395 (lanes 1), AS207 (lanes 2), 2740-80 (CTX^ET-Kn) (lanes 3), O395 cultured with AS207 supernatant (lanes 4), and O395 cultured with 2740-80 (CTX^ET-Kn) supernatant (lanes 5). The Kn^r cassette is slightly larger than the ctxAB genes it replaces in CTX^ET-Knφ, so pCTX^ET-Knφ migrates more slowly than pCTX^ETφ.