Plasmid patterns. Lane 1, S. flexneri strain belonging to subgroup F2; lanes 2 and 3, S. flexneri strains belonging to subgroup F1; lane 4, S. flexneri strain belonging to subgroup F3; lanes 5 and 6, S. flexneri strains belonging to subgroup F4; lane 7, S. flexneri strain belonging to subgroup F5; lane 8, S. flexneri strain belonging to subgroup F6; lane 9, S. flexneri strain belonging to subgroup F7; lanes 10 and 11, S. flexneri strains belonging to subgroups F8 and F9; lane 12, S. dysenteriae; lanes 13 and 14, S. sonnei strains belonging to subgroups S1 and S2.