FIG. 3.

Stability of lytA hybridization pattern during extensive serial cultivation of strains in vitro. Lanes marked λ ladder were loaded with lambda ladder PFGE markers. All isolates are from the United States and were described recently (4). Lanes 1 represent the isolate before extensive serial passage in vitro. Lanes 2 represent the isolate after in vitro passage, as described in Materials and Methods. Numbers in the center indicate molecular sizes in kilobases. (A and C) SmaI digest of total DNA separated by PFGE. (B and D) Hybridization of Southern blots of the gels in panels A and C, respectively, with the lytA gene probe.