Mobile genetic elements in Clostridium difficile and their role in genome function

Abstract

Approximately 11% the Clostridium difficile genome is made up of mobile genetic elements which have a profound effect on the biology of the organism. This includes transfer of antibiotic resistance and other factors that allow the organism to survive challenging environments, modulation of toxin gene expression, transfer of the toxin genes themselves and the conversion of non-toxigenic strains to toxin producers. Mobile genetic elements have also been adapted by investigators to probe the biology of the organism and the various ways in which these have been used are reviewed.

Keywords: Bacteriophage; Conjugative transposon; Horizontal gene transfer; PaLoc; Tn5397; Tn916.

Fig. 1

Comparison of part of CTn5 from C. difficile 630 to the part of Tn6103 that contains the three putative MTns. The red boxes represent homologous genes between CTn5 and Tn6103. The points of insertion of the three putative MTns are represented by the dotted lines. (Figure reproduced from; Brouwer MSM, Warburton PJ, Roberts AP, Mullany P, Allan E. (2011) Genetic organisation, mobility and predicted functions of genes on integrated, mobile genetic elements in sequenced strains of Clostridium difficile. PLoS ONE 6(8): e23014. http://dx.doi.org/10.1371/journal.pone.0023014).

Fig. 2

Demonstration of transfer of the PaLoc. The left panel represents the C. difficile 630 genome. The outer circle represents the C. difficile genome the green bands on the second circle represent 10 kb fragments around the 630 genome that contain snips and indels that differentiate the 630 donor genome from the CD37 recipient genome; the dark blue fragments on the third circle represents the location of CTns the red fragment on the third circle represent the location of the PaLoc, the purple fragments on the third circle represent the location of prophage. The fourth to the tenth circle represent CD37 transconjugants containing the PaLoc, transferred fragments are shown by coloured lines, transferred CTns and PaLocs are shown. The right hand panel shows the region containing the PaLoc in more detail. (for more details see reference [47]). Figure reproduced from; Brouwer MS, Roberts AP, Hussain H, Williams RJ, Allan E, Mullany P. (2013). Horizontal gene transfer converts non-toxigenic Clostridium difficile strains into toxin producers. Nature Communications. 4, 2601.