Seminar series on The Evolution of Genomic Architecture - Tal Dagan: Being a plasmid - consideration of copy number, DNA topology and segregation in plasmid genome evolution

  • Date: Sep 3, 2019
  • Time: 11:00 - 12:00
  • Speaker: Tal Dagan from CAU Kiel, Germany
  • Here you find more information on the speaker:
  • Location: MPI Plön
  • Room: Lecture hall
  • Host: Jenna Gallie & Julien Dutheil


Plasmids are genetic elements that colonize and replicate in prokaryotic cells. Plasmids play a major role in prokaryote ecology and evolution, as they are ubiquitous in all phyla and across all habitats. Plasmids are distinct from chromosomes in several properties, including a relatively small genome size, their ploidy level that can be dynamic, their frequency in the population that can be spatially and temporally heterogeneous, and their mobility. These properties correspond to known determinants of molecular evolution such as mutational supply, segregational drift, population size, and lateral transfer. We studied the fundamental principles that govern plasmid genome evolution using experimental evolution of model plasmids as well as simulated evolution. Our results reveal that segregational drift of multicopy plasmids interferes with the retention and fixation of novel plasmid variants. Depending on the selection pressure on newly emerging variants, plasmid genomes may evolve slower than haploid chromosomes, regardless of their higher mutational supply. Our results further reveal dependency of plasmid stability evolution on the coordination of plasmid transcription and replication, which is challenging in small genomes. Our studies thus reveal plasmid properties that are important for the evolution of successful autonomously replicating genetic elements.
PS: for the phylogenetics enthusiasts – I will include a short report at the end on our current developments on the inference of ancestor-descendant relations in phylogenomics.

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