pIP40a, a type 1 IncC plasmid from 1969 carries the integrative element GI sul2 and a novel class II mercury resistance transposon

摘要

Abstract The 167.5 kb sequence of the conjugative IncC plasmid pIP40a, isolated from a Pseudomonas aeruginosa in 1969, was analysed. pIP40a confers resistance to kanamycin, neomycin, ampicillin, sulphonamides and mercuric ions, and several insertions in a type 1 IncC backbone were found, including copies of IS 3 , Tn 1000 and a novel mercury resistance transposon, Tn 6182 . The antibiotic resistance genes were in two locations. Tn 6023 , containing the aphA1 kanamycin and neomycin resistance gene, is in a partial copy of Tn 1 /Tn 2 /Tn 3 ( bla TEM , ampicillin resistance) in the kfrA gene, and the sul2 sulphonamide resistance gene is in the integrative element GI sul2 in the position of ARI-B islands. The 11.5 kb class II transposon Tn 6182 is only distantly related to other class II transposons, with at most 33% identity between the TnpA of Tn 6182 and TnpA of other group members. In addition, the inverted repeats are 37 bp rather than 38 bp, and the likely resolution enzyme is a tyrosine recombinase (TnpI). Re-annotation of GI sul2 revealed genes predicted to confer resistance to arsenate and arsenite, but resistance was not detected. The location of GI sul2 confirms it as the progenitor of the ARI-B configurations seen in many IncC plasmids isolated more recently. However, GI sul2 has integrated at the same site in type 1 and type 2 IncC plasmids, indicating that it targets this site. Analysis of the distribution of GI sul2 revealed that it in addition to its chromosomal integration site at the 3′-end of the guaA gene, it has also integrated into other plasmids, increasing its mobility. Highlights ? pIP40a, from 1969, is a type 1 IncC plasmids and is one of the oldest known IncC plasmids recovered to-date. ? pIP40a carries genes conferring resistance to sulphonamides, ampicillin, kanamycin, neomycin, and mercuric ions. ? pIP40a is the first IncC plasmid found to carry the integrative element GI sul2 . ? GI sul2 has been independently acquired by type 1 and type 2 plasmids. ? A novel 11.5 kb mercury resistance transposon, Tn 6182 , was found in the pIP40a backbone. ]]>