Evolution of satellite plasmids can prolong the maintenance of newly acquired accessory genes in bacteria

Abstract

Transmissible plasmids spread genes encoding antibiotic resistance and other traits to new bacterial species. Here we report that laboratory populations of Escherichia coli with a newly acquired IncQ plasmid often evolve ‘satellite plasmids’ with deletions of accessory genes and genes required for plasmid replication. Satellite plasmids are molecular parasites: their presence reduces the copy number of the full-length plasmid on which they rely for their continued replication. Cells with satellite plasmids gain an immediate fitness advantage from reducing burdensome expression of accessory genes. Yet, they maintain copies of these genes and the complete plasmid, which potentially enables them to benefit from and transmit the traits they encode in the future. Evolution of satellite plasmids is transient. Cells that entirely lose accessory gene function or plasmid mobility dominate in the long run. Satellite plasmids also evolve in Snodgrassella alvi colonizing the honey bee gut, suggesting that this mechanism may broadly contribute to the importance of IncQ plasmids as agents of bacterial gene transfer in nature.

Deciphering the Structural Diversity and Classification of the Mobile Tigecycline Resistance Gene tet (X)-Bearing Plasmidome among Bacteria

“…S2). This phenomenon was similar to the reported tet(X4)-bearing ColE2-like plasmid p16EC-9K, which was also observed in a polymorphic state of tandem plasmid repeats (57), and this may benefit the transmission of tet(X4) (59). Two additional large-repeat structures, IS26-aadA2lnu(F)-IS26-abh-tet(X4)-ISCR2-floR-tet(A)-oIS26 in 14 kb and oISCR2-erm(42)-ISCR2-abhtet(X4)-ISCR2-floR-IS26 in 20 kb, were found in RF45-2 and RF15-1, respectively.…”

Competition between social cheater viruses is driven by mechanistically different cheating strategies

“…The cheaters that we detected herein are an example of a more general interaction found in the natural world, that of molecular parasites, which are particularly prevalent in microbes, in the form of selfish mobile genetic elements (MGEs). Similar to what has been observed herein, MGEs can have their own parasites, resulting in complex ecological and evolutionary interactions, as has been observed for various MGEs, including satellite plasmids and satellite viruses ( 56 – 58 ). One particularly interesting effect of molecular parasites on evolution is that they may allow the crossing of so-called fitness valleys in the context of fitness landscapes: Parasites may bear genes with mutations that are deleterious to their hosts but that are advantageous to the parasite.…”

The future of self-selecting and stable fermentations

“…Interestingly, the authors [15] did not report structural variant error modes (such as IS element or recombination) as escape mode on this plasmid. Similarly using the power of flow cytometry, the same group also investigated incQ-type plasmids and isolated the emergence of parasitic satellite plasmids that shed the replication genes and expression constructs [67].…”

“…Interestingly, the authors [ 15 ] did not report structural variant error modes (such as IS element or recombination) as escape mode on this plasmid. Similarly using the power of flow cytometry, the same group also investigated incQ-type plasmids and isolated the emergence of parasitic satellite plasmids that shed the replication genes and expression constructs [ 67 ]. Even if uneven segregation of multi-copy plasmids elevate escape rates, single chromosomal gene copies can also be highly vulnerable, as shown through sequencing of vanillin-beta-glucoside producing S. cerevisiae [ 14 ].…”