Insertion sequence ISPst4 activates pUC plasmid replication inPseudomonas stutzeri

Abstract

Insertion sequences (IS) are important drivers of bacterial evolution. Here, we report a previously undescribed IS element (ISPst4) in Pseudomonas stutzeri, and its unusual interaction with plasmids introduced into this species. Transformation of the pUC19 derivative plasmid pUS23 into P. stutzeri yielded ampicillin-resistant transformants in P. stutzeri, but these grew very poorly. Plasmids recovered from the transformants frequently contained insertions of the IS elements ISPst4 and ISPst5. Hybridisation analysis showed that these two IS elements were common in P. stutzeri strains, but were not found in other pseudomonads. Insertions of ISPst4 in pUS23 were found predominantly between bla and oriV, and plasmids with this type of insertion were capable of robust replication in P. stutzeri, unlike pUS23. A promoter-containing region was localised to a 74 bp NcoI-SacI fragment within ISPst4, and we postulate that this promoter drives expression of the pUC oriV in P. stutzeri. This is the first report of IS transposition directly leading to an expansion of the effective host range of a plasmid, adding a new dimension to our understanding of the relationship between plasmids and IS elements.

How Do Transposable Elements Activate Expression of Transcriptionally Silent Antibiotic Resistance Genes?

“…Similar to fusion promoters, complete outward-oriented promoters may play an important role in the expression of TPase genes during transposition of ISs via excised circular intermediates ( Figure 1 c). The occurrence of such promoters has been experimentally confirmed in ISs representing the IS 3 [ 105 ], IS 4 [ 106 ], IS 5 [ 42 ], IS 6 [ 37 ], IS 481 [ 35 ], IS 982 [ 42 ], IS 1380 [ 29 ], and IS L3 [ 107 ] families. A prominent example is the element IS Ecp1 (IS 1380 family), which is responsible for the mobilization for transposition of a number of unrelated antibiotic resistance genes, including several from the bla CTX-M groups, encoding a family of extended-spectrum β-lactamases that are dominant worldwide [ 108 ].…”

The impact of insertion sequences on bacterial genome plasticity and adaptability

“…In Mycobacterium tuberculosis, some evidence has been presented that IS6110 directed the expression of multiple genes (Safi et al 2004). In ampicillin-resistant transformants of P. stutzeri, ISPst4 inserted in pUS23 and presumably promoted transcription of the ori region resulting in robust replication in P. stutzeri (Coleman et al 2014). All outward-directed promoters from IS3-family members are oriented towards their IRR and molecular data (e.g.…”

“…All outward-directed promoters from IS3-family members are oriented towards their IRR and molecular data (e.g. transcription start mapping, deletion and reporter strategies) evidencing a mobile promoter has been provided for IS3, IS6110 and ISPst4 (Charlier et al 1982;Safi et al 2004;Coleman et al 2014).…”

Genomic complexity and plasticity ensurePseudomonassuccess

“…In his MiniReview, Valentin Rybenkov (Rybenkov, ) discusses how the replication, organization, and segregation of the P. aeruginosa chromosome add further complexity to the regulation of the transcriptome. The genetic and phenotypic consequences of plasmids on P. aeruginosa , P. putida, and P. stutzeri are investigated in three different reports by Deraspe et al ., () Silva‐Rocha and de Lorenzo () and Coleman et al ., () respectively, while contributions from Song et al . () and González‐Valdez et al .…”

“…osa, P. putida, and P. stutzeri are investigated in three different reports by Deraspe et al, (2014) Silva-Rocha and de Lorenzo (2014) and Coleman et al, (2014) respectively, while contributions from Song et al (2014) and Gonz alez-Valdez et al (2014) report new findings that influence the regulation of lipopeptide biosynthesis in P. fluorescens and quorum sensing in P. aeruginosa. In all, 12 original reports and MiniReviews are included in this thematic Pseudomonas issue of FEMS Microbiology Letters.…”