FIG. 3.

Southern blot analysis of plasmid DNA from Enterobacter sp. strains 1061 and 1434 and their transconjugants. Plasmid DNA was digested with the SmaI, XhoI, and BamHI endonucleases in lanes 1 to 3, 4 to 6, 7 to 9, and 10 to 12, respectively, and hybridized with TEM-specific (A) and SHV-specific (B) probes. Hybridization with the TEM-specific and SHV-specific probes proves the existence of these genes on the same plasmid. Enterobacter sp. strain 1064 carried two copies of TEM, one of which was transferred together with SHV to the transconjugant. The plasmid of Enterobacter sp. strain 1434 had two copies of SHV, and both were transferred to the transconjugant, together with TEM.