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.
Bottom Line: 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.Integration into rulB on pWW0 occurred at position 6488 generating a 3 bp direct repeat.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)).
Affiliation: Centre for Ecology and Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster, LA1 4AP, UK.Show MeSH
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Mentions: The distribution of ILEs in the environment was assessed in naturally occurring pseudomonads recovered from Copper Mines Valley in the English Lake District (Cumbria, UK). From hundreds of colony-forming units (CFU) initially isolated on Pseudomonas selective agar, 800 presumptive pseudomonad isolates were purified. Isolates were not characterized further and, because of the isolation media used, are not guaranteed to be independent isolates. Purified isolates were screened for similar ILEs by colony hybridization using the entire pFBA1001 10 kb PstI restriction fragment as a DNA probe. This resulted in 11 positive signals (1.4%; not shown). Conjugation of hybridization positive strains with P. putida PaW340 (pWW0) resulted in the insertion of regions of approximately 9–16 kb in size into pWW0 in 5 of the 11 isolates. In each case, the frequency of plasmid transfer ranged between 10−4 and 10−2 per recipient. Restriction fragment length polymorphism (RFLP) profiling showed that all altered pWW0 plasmids were different, and it was therefore assumed that all six ILEs were different (Fig. 1). The original bacterial isolates containing these ILEs were designated strains FH1–FH6 (Table 1), and the altered pWW0 plasmids that arose after mating with P. putida PaW340 (pWW0) were named pWW0::ILEFH1–6.
Affiliation: Centre for Ecology and Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster, LA1 4AP, UK.