killing the host. This highly evolved and sophisticated target-site selection pathway suggests this pathway evolved to promote coexistence between the transposon and it host, as well as Tn7's successful transmission into future generations of bacterium. The Tn7 transposon is 14 kb long and codes for five enzymes. The ends of the DNA sequence consists of two segments that the Tn7 transposase interacts with during recombination. The left segment (Tn7-L) is 150 bp long and the right sequence (Tn7-R) is 90 bp long. Both ends of the transposon contain a series of 22 bp binding sites that the Tn7 transposase recognizes and binds to. Within the transposon are five discrete genes encoding for proteins that make up the transposition machinery. In addition, the transposon contains an integron, a DNA segment containing several cassettes of genes encoding for antibiotic-resistance. The Tn7 transposon codes for five proteins: TnsA, TnsB, TnsC, TnsD, and TnsE. TnsA and TnsB interact together to form the Tn7 transposase enzyme TnsAB. The enzyme specifically recognizes and binds to the ends of the DNA sequence of the transposon, and excises it by introducing double-stranded DNA breaks to each end. The excised sequence is then inserted to another target DNA site. Much like other characterized transposons, the mechanism for Tn7 transposition involves cleavage of the 3' ends from the donating DNA by the TnsA protein of the TnsAB transposase. However, Tn7 is also uniquely cleaved near the 5' ends, about 5 bp from the 5' end towards the Tn7 transposon, by the TnsB protein of TnsAB. After the insertion of the transposon into the target DNA site, the 3' ends are covalently linked to the target DNA, but the 5 bp gaps are still present at the 5' ends. As a result, repair of these gaps leads to a further 5 bp duplication at the target site. The TnsC protein interacts with the transposase enzyme and the target DNA to promote the excision and insertion processes. The ability of TnsC to activate the transposase depends on its interaction with a target DNA along with its appropriate targeting protein, TnsD or TnsE. The TnsD and TnsE proteins are alternative target selectors that are also DNA binding activators that promote excision and insertion of Tn7. Their ability to interact with a particular target DNA is key to the target-site selection of Tn7. The proteins TnsA, TnsB, and TnsC thus form the core machinery