An updated view of plasmid conjugation and mobilization inStaphylococcus

Abstract

The horizontal gene transfer facilitated by mobile genetic elements impacts almost all areas of bacterial evolution, including the accretion and dissemination of antimicrobial-resistance genes in the human and animal pathogen Staphylococcus aureus. Genome surveys of staphylococcal plasmids have revealed an unexpected paucity of conjugation and mobilization loci, perhaps suggesting that conjugation plays only a minor role in the evolution of this genus. In this letter we present the DNA sequences of historically documented staphylococcal conjugative plasmids and highlight that at least 3 distinct and widely distributed families of conjugative plasmids currently contribute to the dissemination of antimicrobial resistance in Staphylococcus. We also review the recently documented “relaxase-in trans” mechanism of conjugative mobilization facilitated by conjugative plasmids pWBG749 and pSK41, and discuss how this may facilitate the horizontal transmission of around 90% of plasmids that were previously considered non-mobilizable. Finally, we enumerate unique sequenced S. aureus plasmids with a potential mechanism of mobilization and predict that at least 80% of all non-conjugative S. aureus plasmids are mobilizable by at least one mechanism. We suggest that a greater research focus on the molecular biology of conjugation is essential if we are to recognize gene-transfer mechanisms from our increasingly in silico analyses.

Regulation of conjugative transfer of plasmids and integrative conjugative elements

“…Also, some plasmids or ICEs can be mobilized by other genetic elements. The mobilization may be due to the participation of proteins, which can act in trans (O'Brien et Ramsay et al, 2016;Torres Tejerizo et al, 2014), or through cointegration of the different elements Haskett et al, 2016). The expression of transfer genes may be regulated through diverse mechanisms in different plasmids and ICEs.…”

Ordering the mob: Insights into replicon and MOB typing schemes from analysis of a curated dataset of publicly available plasmids

“…Replicons include various different loci, none of which are universal across plasmids (del Solar et al, 1998), whereas relaxases are thought to be universally present amongst plasmids that mobilise via the relaxase- in - cis mechanism (Garcillán-Barcia et al, 2011, Ramsay et al, 2016). However, relaxase homology can be distant, even amongst plasmids of the same MOB type (Garcillán-Barcia et al, 2009).…”

Draft Genome Sequence of <b><i>Bacillus cereus</i></b> CITVM-11.1, a Strain Exhibiting Interesting Antifungal Activities

“…The acquisition of antimicrobial-resistance genes in bacteria can occur by means of self-transmissible plasmids (conjugative plasmids). These plasmids usually harbor all the genes involved in mating-pore formation as well as the essential mob gene (encoding DNA relaxase), and the recognition sequence commonly known as origin of transfer (oriT) [Ramsay et al, 2016]. Despite the mob gene being found in the pBC11.1 plasmid, we could not effectively predict any known putative oriT sequence in this plasmid.…”