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

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 IS3, Tn1000 and a novel mercury resistance transposon, Tn6182. The antibiotic resistance genes were in two locations. Tn6023, conAntibiotic resistance Transposon taining the aphA1 kanamycin and neomycin resistance gene, is in a partial copy of Tn1/Tn2/Tn3 (bla TEM, ampicillin resistance) in the kfrA gene, and the sul2 sulphonamide resistance gene is in the integrative element GIsul2 in the position of ARI-B islands. The 11.5 kb class II transposon Tn6182 is only distantly related to other class II transposons, with at most 33% identity between the TnpA of Tn6182 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 GIsul2 revealed genes predicted to confer resistance to arsenate and arsenite, but resistance was not detected. The location of GIsul2 confirms it as the progenitor of the ARI-B configurations seen in many IncC plasmids isolated more recently. However, GIsul2 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 GIsul2 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.

Mobile Genetic Elements Associated with Antimicrobial Resistance

“…intI encodes an atypical site-specific tyrosine recombinase, which has an extra domain compared to other members of this family (112), that catalyzes recombination between the attI site of the integron and the attC site of a (109,110) and on sequences from the following INSDC accession numbers: Tn6022, CP012952; Tn6021 and Tn6164, CP012005; Tn6022Δ, JN247441; Tn6172, KU744946; and Tn6019, FJ172370. (E) GIsul2 (15.460 kb [188] rather than the initially reported 15.456 kb [61], apparently due to errors in the S. flexneri sequence). ars, arenite/arsenate resistance gene; TA, toxin-antitoxin system; alpA, regulation gene.…”

“…The conjugation genes are related to trb genes of IncP␣ plasmids, suggesting an interaction with these plasmids (188). GIsul2 was reported to be present in the chromosomes of S. flexneri and E. cloacae isolates (61) and as the progenitor of the ARI-B resistance region on C plasmids (188). Searches now identify a complete GIsul2 in E. coli and other Enterobacteriaceae.…”

“…GIsul2 (Fig. 4E) carries int (tyrosine site-specific recombinase) and resG (resolvase) genes and genes encoding potential replication, conjugation, and TA proteins, plus putative arsenate/arsenite resistance protein genes and ISCR2-sul2 (61,188,446). The conjugation genes are related to trb genes of IncP␣ plasmids, suggesting an interaction with these plasmids (188).…”

“…4E) carries int (tyrosine site-specific recombinase) and resG (resolvase) genes and genes encoding potential replication, conjugation, and TA proteins, plus putative arsenate/arsenite resistance protein genes and ISCR2-sul2 (61,188,446). The conjugation genes are related to trb genes of IncP␣ plasmids, suggesting an interaction with these plasmids (188). GIsul2 was reported to be present in the chromosomes of S. flexneri and E. cloacae isolates (61) and as the progenitor of the ARI-B resistance region on C plasmids (188).…”

The Obscure World of Integrative and Mobilizable Elements, Highly Widespread Elements that Pirate Bacterial Conjugative Systems

“…In a similar way, although they are not related to SGI1, three adjacent genes of the putative MGI GI Sul2 and its relatives from various Gammaproteobacteria, encode proteins related to TrbJ (VirB5), TrbK (protein exclusion entry) and TrbL (VirB6) MPF T subunits from IncP1-α plasmids [ 36 ]. Like SGI1, they do not encode any other protein related to relaxase, other relaxosome proteins, CP nor other MPF subunits.…”