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: 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.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.
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.