title: Sequencing of IncX-plasmids suggests ubiquity of mobile forms of a biofilm-promoting gene cassette recruited from Klebsiella pneumoniae.
abstract: Plasmids are a highly effective means with which genetic traits that influence human health, such as virulence and antibiotic resistance, are disseminated through bacterial populations. The IncX-family is a hitherto sparsely populated group of plasmids that are able to thrive within Enterobacteriaceae. In this study, a replicon-centric screening method was used to locate strains from wastewater sludge containing plasmids belonging to the IncX-family. A transposon aided plasmid capture method was then employed to transport IncX-plasmids from their original hosts (and co-hosted plasmids) into a laboratory strain (Escherichia coli Genehogs®) for further study. The nucleotide sequences of the three newly isolated IncX-plasmids (pLN126_33, pMO17_54, pMO440_54) and the hitherto un-sequenced type-plasmid R485 revealed a remarkable occurrence of whole or partial gene cassettes that promote biofilm-formation in Klebsiella pneumonia or E. coli, in all four instances. Two of the plasmids (R485 and pLN126_33) were shown to directly induce biofilm formation in a crystal violet retention assay in E. coli. Sequence comparison revealed that all plasmid-borne forms of the type 3 fimbriae encoding gene cassette mrkABCDF were variations of a composite transposon Tn6011 first described in the E. coli IncX plasmid pOLA52. In conclusion, IncX-plasmids isolated from Enterobacteriaceae over almost 40 years and on three different continents have all been shown to carry a type 3 fimbriae gene cassette mrkABCDF stemming from pathogenic K. pneumoniae. Apart from contributing general knowledge about IncX-plasmids, this study also suggests an apparent ubiquity of a mobile form of an important virulence factor and is an illuminating example of the recruitment, evolution and dissemination of genetic traits through plasmid-mediated horizontal gene transfer.
authors: Department of Biology, University of Copenhagen, Copenhagen, Denmark. burmolle@bio.ku.dk
authors: Mette
authors: M
authors: Burmølle
authors: Anders
authors: A
authors: Norman
authors: Søren J
authors: SJ
authors: Sørensen
authors: Lars Hestbjerg
authors: LH
authors: Hansen
mesh_terms: D018441:Biofilms / Q000254:growth & development*; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology; D022761:Gene Transfer, Horizontal / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics*; D007711:Klebsiella pneumoniae / Q000235:genetics* / Q000502:physiology*; D010957:Plasmids / Q000235:genetics*; D012093:Replicon / Q000235:genetics; D017422:Sequence Analysis, DNA; D014865:Waste Disposal, Fluid; D062065:Wastewater / Q000382:microbiology
chemical_list: D062065:Wastewater