[14/14] pRUM-like plasmids continue to diversify through the actions of IS1216 and other small MGEs

These adaptable MDR platforms contribute to the success of CC17 E. faecium, and have the potential to enter other clones, species or genera through cointegrate formation + HGT

Thanks for reading!

[13/14] We propose a model for the IS1216-mediated evolution of the pRUM-like lineage from pCANE via an intermediate we call pMOLASSES

This seems to have involved an evolutionary trade-off, swapping transfer ability for the plasticity of the IS1216 accessory region 🤔 more on this in the paper!

[12/14] The 1990s plasmid matched the pRUM backbone almost perfectly, but it was larger and didn’t contain IS1216… instead of an accessory region, it had 44 kb that looked like backbone and contained putative conjugation determinants 🚀

This looked like the ancestor of pRUM, so we called it pCANE

[9/14] Importantly, we saw lots of cointegrate formation, generating structures comprised of parts from usually distinct plasmids

IS26 family elements are great at this!

Several small plasmids have been rolled into pRUM-like structures, including pCOLA and pDRY, named after popular rum mixers 🍹

[8/14] Examining plasmid structures revealed enormous variation!

Most was in the accessory region, which ranged in size from 809 bp (a lone IS1216) to 285 kb, and included all sorts of acquired genes

Multiple IS1216-mediated deletions have also removed adjacent parts of the backbone

[7/14] We screened GenBank and found 150 complete pRUM-like plasmid sequences

Their mostly E. faecium hosts were isolated from various sources around the world, and represented an array of STs… though all but one were E. faecium CC17

[3/14] Two plasmids caught my eye: pHHEf1 and pHHEf2

Their pRUM-like backbones were identical, with ARG-bearing accessory regions in exactly the same position, but the content of those regions was totally different!

Strikingly, both were bounded by copies of the insertion sequence IS1216…