In all occurrences the resistance gene was confined to a conserved 3378 bp region that included an adjacent tyrosine-type integrase (tyr-Int or In; brown arrows), defining the smallest unit transposon. Analysing the adjacent environment using ISfinder these unit transposons were located on inserts of various lengths bordered by a variety of IS elements (purple arrows). These could largely be classified as ( A ) minimal: 5132-5902 bp; B small: 14,539-17,400 bp (although NK-BR1052 was truncated by contig assembly); C intermediate: 25,862-30,548 bp (which includes a region of 20,215 bp homologous) to a Enterobacter roggenkampii plasmid (GenBank Accession number CP116250) containing a cassette of tellurite resistance genes (green arrows); and ( D ) complex regions of >50,000 bp, two of which include the Enterobacter roggenkampii plasmid tellurite resistance cassette, as well as genes from the tra family of conjugal elements (light blue arrows). Two of these isolates have >20,000 bp regions with high homology to a tra gene family cassette carried by an unnamed plasmid in Enterobacter sp. Z1 (Genbank accession number CP099720). No consistent pattern of boundary IS elements could be discerned to account for a larger conserved mobile element. Yellow arrows indicate open-reading frames that could not be ascribed resistance or mobility but were interspersed between other genes of interest. A full annotation of these regions is not included to highlight areas of greater interest.
