Conservation of the region 3′ to gnd in E. coli O55 strains in diverse lineages. EcoRV-digested bacterial DNA was electrophoresed and probed in Southern blots. The probe consists of the 3′ end of the O55:H7 gnd and regions I and II in Fig. 4. (A) DNA from E. coli HB101 (lane 1), DEC lineage 5 E. coli O55 H7 strains TB182A, TB156A, DEC 5A, 5B, 5C, 5D, and 5E (lanes 2 to 8, respectively), DEC lineage 1 E. coli O55:H6 strains 1A and 1B (lanes 9 and 10, respectively), and DEC lineage 2 E. coli O55:H6 strains 2A and 2B (lanes 11 and 12, respectively). Arrows indicate conserved EcoRV fragments corresponding to region II DNA between the arrows in Fig. 4. (B) DNA from E. coli O157:H7 (lane 1) and E. coli O55:H7 (lane 2). Arrows indicate O157:H7 fragments with predicted homology to the probe.