Abstract
IncI-complex plasmids can be divided into seven subgroups IncI1, IncI2, IncIγ, IncB/O, IncK1, IncK2, and IncZ. In this study, a replicon-based scheme was proposed for typing IncI-complex plasmids into four separately clustering subgroups IncI2, IncI1/B/O, IncIγ/K1 and IncK2/Z, the last three of which were combined from IncI1 and IncB/O, IncIγ and IncK1, and IncK2 and IncZ, respectively. Four IncIγ/K1 plasmids p205880-NR2, p14E509-CTXM, p11011-CTXM and p61806-CTXM were fully sequenced and compared with IncIγ/K1 reference pCT, IncI2 reference R721, IncI1/B/O reference R64 and IncK2/Z reference pO26-CRL-125. These plasmids shared conserved gene organization in the replication and conjugal transfer regions, but displaying considerable sequence diversity among different subgroups. Remarkable modular differences were observed in the maintenance and transfer leading regions. p205880-NR2 contained no resistance genes or accessory modules, while the other seven plasmids acquired one or more accessory modules, which harbored mobile elements [including unit transposons, insertion sequence (IS)-based transposition units and individual IS elements] and associated resistance markers (especially including those involved in resistance to β-lactams, aminoglycosides, tetracyclins, phenicols, streptomycins, trimethoprims, sulphonamides, tunicamycins and erythromycins). Data presented here provided a deeper insight into diversification and evolution of IncI-complex plasmids.
Highlights
Plasmids of the I incompatibility complex (IncI-complex) produce I-type pili
Genomic DNA was isolated from each isolate using a Qiagen Blood & Cell Culture DNA Maxi Kit (Qiagen, Hilden, Germany)
The genomic DNA of strain 61806 was sequenced from a mate-pair libraries with average insert size of 5 kb using a MiSeq sequencer (Illumina, CA, United States)
Summary
Plasmids of the I incompatibility complex (IncI-complex) produce I-type pili. Based on morphological and serological similarities of their pili, IncI-complex plasmids can be divided into at least seven subgroups, namely IncI1 ( = IncIα or Com1), IncI2 ( = IncIδ), IncIγ, IncB/O, IncK1, IncK2, and IncZ (Tschäpe and Tietze, 2010; Papagiannitsis et al, 2011; Rozwandowicz et al, 2017). IncI-complex plasmids are low copy-number, narrow-host-range, conjugative plasmids, varying in size from 50 to 250 kb. Comparative Genomics Analysis of IncIγ/K1 Plasmids into regions of replication, maintenance, transfer leading and conjugal transfer (Sampei et al, 2010). The partitioning genes parA and parB in the maintenance region are responsible for active partition of replicated DNA into daughter cells during cell division. A multiple inversion system named shufflon mediates rearrangement of PilV protein by a plasmidencoded site-specific recombinase Rci (Komano et al, 1987). This recombination event selects one of seven different pilV genes, which is responsible for the determination of recipient specificity (Komano et al, 1994)
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