%0 Journal Article %A Haines, Anthony S. %A Akhtar, Parveen %A Stephens, Elton R. %A Jones, Karen %A Thomas, Christopher M. %A Perkins, Caroline D. %A Williams, Jacqueline R. %A Day, Martin J. %A Fry, John C. %T Plasmids from freshwater environments capable of IncQ retrotransfer are diverse and include pQKH54, a new IncP-1 subgroup archetype %D 2006 %J Microbiology, %V 152 %N 9 %P 2689-2701 %@ 1465-2080 %R https://doi.org/10.1099/mic.0.28941-0 %I Microbiology Society, %X Nine mercury-resistance plasmids isolated from river epilithon were assessed for their ability to retrotransfer the non-conjugative IncQ plasmid, R300B, derivatives of which have commercial uses that may result in accidental or deliberate release into the environment. Retrotransfer frequencies ranging from 2.1×10−4 to 1.75×10−5 were obtained for five of the nine plasmids – the remaining plasmids showed low or undetectable retrotransfer ability. The majority of the retrotransfer-proficient plasmids could not be classified by the tests used. Classical incompatibility testing with RP4 identified pQKH6, pQKH54 and pQM719 as IncP-1. Hybridization to replicon probes confirmed this for pQKH6 and pQM719 and added pQKH33. PCR with primers designed to amplify trfA and korA regions of IncP-1 plasmids did not identify any other plasmids. Plasmids pQKH6 and pQM719 but not pQKH54 produced similar SphI restriction profiles to the IncP-1β subgroup. The complete nucleotide sequence of pQKH54 was determined, revealing it to have a complete IncP-1 backbone but belonging to a new distinct subgroup which was designated IncP-1γ. The results emphasize the ubiquity and diversity of IncP-1 plasmids in the environment but demonstrate that plasmids of as yet unknown groups are also able to retrotransfer IncQ plasmids efficiently. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.28941-0