IS <i>26</i> -Mediated Formation of Transposons Carrying Antibiotic Resistance Genes

<jats:p> In Gram-negative bacteria, IS <jats:italic>26</jats:italic> recruits antibiotic resistance genes into the mobile gene pool by forming transposons carrying many different resistance genes. In addition to replicative transposition, IS <jats:italic>26</jats:italic> was recently shown to use a novel conservative movement mechanism in which an incoming IS <jats:italic>26</jats:italic> targets a preexisting one. Here, we have demonstrated how IS <jats:italic>26</jats:italic> -bounded class I transposons can be produced from translocatable units (TUs) containing only an IS <jats:italic>26</jats:italic> and a resistance gene via the conservative reaction. TUs were incorporated next to an existing IS <jats:italic>26</jats:italic> , creating a class I transposon, and if the targeted IS <jats:italic>26</jats:italic> is in a transposon, the product resembles two transposons sharing a central IS <jats:italic>26</jats:italic> , a configuration observed in some resistance regions and when a transposon is tandemly duplicated. Though homologous recombination could also incorporate a TU, Tnp26 is far more efficient. This provides insight into how IS <jats:italic>26</jats:italic> builds transposons and brings additional transposons into resistance regions. </jats:p>