Figure 1.

A generalised structure of (a) usual integrons and (b) unusual, or reverse integrons. The green arrows indicate the primer binding sites on the unusual integron structure of T. denticola. The grey and blue open arrowed boxes represent integrase gene (intI) and the open reading frames (ORFs), respectively, pointing in the direction of transcription. The promoters, P_intI and P_C, were represented by black arrows. The recombination sites, attI and attC, were represented by yellow and orange circles, respectively.