FIG. 1.

Diagrammatic representation of the restriction patterns seen on Southern blots of DNA from different strains, which was hybridized with a probe that detects the tetQ rteA rteB rteC region of the CTnDOT type CTn's. The fragment sizes and the locations of the genes within the 7.7-kbp EcoRI fragment used as the probe are shown at the top. Pattern A has the restriction fragment profile of CTnDOT and closely related elements. Some of the CTnDOT family of elements (CTnERL2) lack an EcoRV site and have the fragment labeled RV∗. This pattern is referred to as A′. Occasionally this EcoRV site does not cut completely, and a mixed pattern is observed (indicated as A∗ in the Southern blot in Fig. 2). Strains exhibiting pattern B are missing the two small rteC fragments (C_0.2 and C_0.64 in Fig. 2), and all of the rteC homology is located in the 2.6-kbp fragment labeled BC_2.6 in Fig. 2. Strains that exhibit the C pattern are heterogeneous. A few lack rteC completely (CTn7853; C3 in Fig. 2), and others just have a very different pattern, but all of the genes on the probe are present (CTnV479; C2 in Fig. 2). Pattern D is rare; these strains have tetQ and usually neither rteB nor rteC sequences. The percentage of the 60 strains exhibiting each of the patterns is shown at the right.