Destabilization of IncA and IncC plasmids by SGI1 and SGI2 type Salmonella genomic islands

• Published in: Plasmid Vol. 87-88; pp. 51 - 57
• Main Authors: Harmer, Christopher J., Hamidian, Mohammad, Ambrose, Stephanie J., Hall, Ruth M.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.09.2016
• Subjects: Conjugation, Genetic; Epistasis, Genetic; Escherichia coli; Gene Order; Genome, Bacterial; Genomic Instability; Genomic Islands; IncA plasmid RA1; IncC plasmid pRMH760; Plasmid loss; Plasmids - genetics; Salmonella - genetics; Salmonella enterica; Salmonella genomic islands SGI1 and SGI2; Plasmid loss; IncC plasmid pRMH760; Salmonella genomic islands SGI1 and SGI2; IncA plasmid RA1
• ISSN: 0147-619X; 1095-9890
• DOI: 10.1016/j.plasmid.2016.09.003

Both the Salmonella genomic islands (SGI) and the conjugative IncC plasmids are known to contribute substantially to the acquisition of resistance to multiple antibiotics, and plasmids in the A/C group are known to mobilize the Salmonella genomic island SGI1, which also carries multiple antibiotic resistance genes. Plasmid pRMH760 (IncC; A/C2) was shown to mobilize SGI1 variants SGI1-I, SGI1-F, SGI1-K and SGI2 from Salmonella enterica to Escherichia coli where it was integrated at the preferred location, at the end of the trmE (thdF) gene. The plasmid was transferred at a similar frequency. However, we observed that co-transfer of the SGI and the plasmid was rarer. In E. coli to E. coli transfer, the frequency of transfer of the IncC plasmid pRMH760 was at least 1000-fold lower when the donor carried SGI1-I or SGI1-K, indicating that the SGI suppresses transfer of the plasmid. In addition, pRMH760 was rapidly lost from both E. coli and S. enterica strains that also carried SGI1-I, SGI1-F or SGI2. However, plasmid loss was not seen when the SGI1 variant was SGI1-K, which lacks two segments of the SGI1 backbone. The complete sequence of the SGI1-I and SGI1-F were determined and SGI1-K also carries two single base substitutions relative to SGI1-I. The IncA (A/C1) plasmid RA1 was also shown to mobilize SGI2-A and though there are significant differences between the backbones of IncA and IncC plasmids, RA1 was also rapidly lost when SGI2-A was present in the same cell. We conclude that there are multiple interactions, both cooperative and antagonistic, between an IncA or IncC plasmid and the SGI1 and SGI2 family genomic islands. •IncA and IncC plasmids interact in several ways with variants of genomic island SGI1 and SGI2.•Conjugative IncA plasmid RA1 and IncC plasmid pRMH760 mobilized SGI1 and SGI2 variants.•SGI1 and SGI2 destabilized IncA and IncC plasmids leading to complete loss of the plasmid.•SGI1 variants suppressed conjugative transfer of the IncC plasmid.