The rulB gene of plasmid pWW0 is a hotspot for the site-specific insertion of integron-like elements found in the chromosomes of environmental Pseudomonas fluorescens group bacteria
Wiley for Society for Applied Microbiology (SfAM)
© 2013 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. https://creativecommons.org/licenses/by/4.0/
The rulAB operon of Pseudomonas spp. confers fitness traits on the host and has been suggested to be a hotspot for insertion of mobile elements that carry avirulence genes. Here, for the first time, we show that rulB on plasmid pWW0 is a hotspot for the active site-specific integration of related integron-like elements (ILEs) found in six environmental pseudomonads (strains FH1-FH6). Integration into rulB on pWW0 occurred at position 6488 generating a 3 bp direct repeat. ILEs from FH1 and FH5 were 9403 bp in length and contained eight open reading frames (ORFs), while the ILE from FH4 was 16 233 bp in length and contained 16 ORFs. In all three ILEs, the first 5.1 kb (containing ORFs 1-4) were structurally conserved and contained three predicted site-specific recombinases/integrases and a tetR homologue. Downstream of these resided ORFs of the 'variable side' with structural and sequence similarity to those encoding survival traits on the fitness enhancing plasmid pGRT1 (ILE(FH1) and ILE(FH5)) and the NR-II virulence region of genomic island PAGI-5 (ILE(FH4)). Collectively, these ILEs share features with the previously described type III protein secretion system effector ILEs and are considered important to host survival and transfer of fitness enhancing and (a)virulence genes between bacteria.
The authors wish to thank the Natural Environment Research Council via the Freshwater Biological Association, and Centre for Ecology and Hydrology for funding this research. We are also grateful to Dr Maria Kivisaar of Tartu University, Estonia for the provision of strain P. putida PaW85 (pWW0ΔrulAB::KmR); Dr Tiffany Brooke Taylor at the University of Reading for technical assistance and to Allan Nelson and Mike Wilson for critical evaluation of this manuscript.
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Vol. 16 (8), pp. 2374 - 2388
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