Diverse mobilized class 1 integrons are common in the chromosomes of pathogenic Pseudomonas aeruginosa clinical isolates

Abstract

Eleven clinical class 1 integron-containing Pseudomonas aeruginosa isolates from Australia and Uruguay were investigated for the genomic locations of these elements. Several novel class 1 integrons/transposons were found in at least four distinct locations in the chromosome, including genomic islands. These elements seem to be undergoing successful dispersal by lateral gene transfer since integrons were identified across several lineages and more than one clonal line.

Fig 1

Structure of Tn6162 in comparison to that of Tn6060. Numbered horizontal lines indicate regions common to Tn6060 and Tn6162. (A) Tn6060. This is a modified version of Fig. 1 from Roy Chowdhury et al. (21). See also accession number GQ161847. Top line depicts the transposon backbone in which the integron (bottom line) is inserted. Vertical arrow indicates the point of insertion. The filled vertical rectangles indicate inverted repeats (IRs) as shown. Filled horizontal arrows represent genes or operons and the direction of transcription. The filled diamond is the attI1 site, and the filled ovals are the attC sites. Gene designations are as described in the text. (B) Tn6162. The general organization is as for Tn6060.

Fig 2

Structure of Tn6163 and its genetic context. The general organization and symbols are as for Fig. 1. Tn6163, IS4-like element with 62% protein identity to accession number NC_007336.1. aacA4-like gene cassette with 25 nucleotides replacing nucleotides 1 to 24 of the standard cassette. GI2, genomic island 2. PAO2583 is a gene located in the core P. aeruginosa genome (accession number AE004091) and is the inferred position of GI2 based on the known location of LESGI-3 (26), which is highly similar to GI2.

Fig 3

Structure and location of IS26-associated integrons. The general organization and symbols are as for Fig. 1. (A) Strain U09. oprDΔ is an insertionally inactivated oprD gene. PAO958 is a gene located in the core P. aeruginosa genome (accession number AE004091). (B) HEAR2053 refers to a conserved hypothetical protein (accession number CAL62196.1), and HEAR2054 refers to a DNA integrase (nonintegron) protein (accession number CAL62197.1) located in the genome of a Herminiimonas arsenicoxydans strain. The corresponding encoded proteins found here match most closely to these. PAO2820 is a gene located in the core P. aeruginosa genome (accession number AE004091).