Figure 1

Phylogenetic distribution of integron- and pseudointegron-containing bacteria. Lineages colored in green represent integron positive lineages; purple represents lineages with pseudointegrons, and black represents lineages without integrons (organisms which have been entirely sequenced and contain no intI gene). Species that contain pseudo and functional integrons are colored both purple and green. 16S rRNA genes from all integron positive (functional and pseudo) and integron negative organisms in the eighteen bacterial orders in which integrons are found were aligned using the NAST aligner [64]. The tree was constructed in PAUP [61] using the NJ algorithm using the best-fit model of sequence evolution calculated in MODELTEST [66]. Orders and major bacterial phyla are indicated. Tree was rooted using five archaeal 16S rRNA gene sequences: Pyrobaculum clidifontis, Aeropyrum pernix, soil clone cren34kb, Methanobacterium thermoautotrophicum, and Methanosphaera stadtmanae from the Greengenes [64] alignment.