Sequence of events that led to the formation of RD1 in EAHEC O104:H4 isolates 2009EL-2050 from the Republic of Georgia and 2011C-3493, the German HUS representative isolate.

<p>A: Events that shaped RD1 in 2009EL-2050. The progenitor was modified by IS<i>26</i> inserting into the <i>tnpM</i> gene creating a characteristic eight base duplication followed by the inversion of a fragment of DNA bounded by two IS<i>26</i> elements and containing a deleted class 1 integron. These events created a new composite IS<i>26</i> transposon, Tn<i>6222</i>. Direct repeats and reverse complementary sequences generated by IS<i>26</i> mediated events are depicted with square brackets [CAATGCGC] and the class 1 integron within curved brackets {TCCAT}. B: Events that shaped RD1 in 2011C-3493. Insertion of IS<i>26</i> within the IR_L of an existing IS<i>26</i> in the progenitor CRL followed by a deletion of <i>bla</i>_TEM-1 gene containing module in Tn<i>6029</i>C generated the unique CRL depicted in the outbreak isolate 2011C-3493 and led to the formation of the novel transposon Tn<i>6223</i> (bottom panel). The 12 bp sequence within Tn<i>6223</i> is a unique signature created by the deletion of the proposed <i>bla</i>_TEM-1 gene containing fragment within Tn<i>6029C</i>. The asterisk on the underlined sequences within Tn<i>6223</i> is the portion which is identical to IR_L of IS<i>26</i> and the remaining eight of the 12 bases indicate the eight base region which abuts the IS<i>26</i> at the other end.