scholarly journals Segregational drift and the interplay between plasmid copy number and evolvability

2018 ◽  
Author(s):  
Judith Ilhan ◽  
Anne Kupczok ◽  
Christian Woehle ◽  
Tanita Wein ◽  
Nils F. Hülter ◽  
...  
Keyword(s):  
Cell Division ◽  
Copy Number ◽  
Plasmid Copy Number ◽  
Fixation Time ◽  
Multicopy Plasmid ◽  
Plasmid Copy ◽  
Plasmid Evolution ◽  
Host Chromosome ◽  
Daughter Cells ◽  
Multiple Copies

AbstractThe ubiquity of plasmids in all prokaryotic phyla and habitats and their ability to transfer between cells marks them as prominent constituents of prokaryotic genomes. Many plasmids are found in their host cell in multiple copies. This leads to an increased mutational supply of plasmid-encoded genes and genetically heterogeneous plasmid genomes. Nonetheless, the segregation of plasmid copies into daughter cells during cell division is considered to occur in the absence of selection on the plasmid alleles. We investigate the implications of random genetic drift of multicopy plasmids during cell division – termed here segregational drift – to plasmid evolution. Performing experimental evolution of low- and high-copy non-mobile plasmids in Escherichia coli, we find that the evolutionary rate of multicopy plasmids does not reflect the increased mutational supply expected according to their copy number. In addition, simulated evolution of multicopy plasmid alleles demonstrates that segregational drift leads to increased loss frequency and extended fixation time of plasmid mutations in comparison to haploid chromosomes. Furthermore, an examination of the experimentally evolved hosts reveals a significant impact of the plasmid type on the host chromosome evolution. Our study demonstrates 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. We suggest that plasmid copy number is an important determinant of plasmid evolvability due to the manifestation of segregational drift.

scholarly journals Quantitative characterization of random partitioning in the evolution of plasmid-encoded traits

2019 ◽  
Author(s):  
Andrew D. Halleran ◽  
Emanuel Flores-Bautista ◽  
Richard M. Murray
Keyword(s):  
Copy Number ◽  
Plasmid Copy Number ◽  
Stochastic Simulations ◽  
Quantitative Characterization ◽  
Plasmid Copy ◽  
Daughter Cells ◽  
Copy Numbers ◽  
Plasmid Partitioning ◽  
Beneficial Allele

AbstractPlasmids are found across bacteria, archaea, and eukaryotes and play an important role in evolution. Plasmids exist at different copy numbers, the number of copies of the plasmid per cell, ranging from a single plasmid per cell to hundreds of plasmids per cell. This feature of a copy number greater than one can lead to a population of plasmids within a single cell that are not identical clones of one another, but rather have individual mutations that make a given plasmid unique. During cell division, this population of plasmids is partitioned into the two daughter cells, resulting in a random distribution of different plasmid variants in each daughter. In this study, we use stochastic simulations to investigate how random plasmid partitioning compares to a perfect partitioning model. Our simulation results demonstrate that random plasmid partitioning accelerates mutant allele fixation when the allele is beneficial and the selection is in an additive or recessive regime where increasing the copy number of the beneficial allele results in additional benefit for the host. This effect does not depend on the size of the benefit conferred or the mutation rate, but is magnified by increasing plasmid copy number.

Bacterial fitness and plasmid loss: the importance of culture conditions and plasmid size

1998 ◽  
Vol 44 (4) ◽  
pp. 351-355 ◽  
Author(s):  
M Alex Smith ◽  
Michael J Bidochka
Keyword(s):  
Copy Number ◽  
Luria Broth ◽  
Plasmid Copy Number ◽  
Culture Conditions ◽  
Lag Phase ◽  
Multicopy Plasmid ◽  
Plasmid Copy ◽  
Plasmid Loss ◽  
Bacterial Fitness ◽  
Plasmid Size

Several pBluescript-derived plasmids of various sizes were constructed to study the effects of multicopy plasmid size on bacterial fitness and plasmid loss. Transformed and untransformed bacterial clones were grown in media with or without ampicillin. Bacterial fitness (measured by growth rate), plasmid presence or absence, and plasmid copy number were assessed during successive subculturings. In selective media (minimal medium or Luria Broth plus ampicillin), the clone transformed with the largest plasmid (pBluescript with a 9000-bp insert) had a significantly longer lag phase than all other clones. In nonselective media the rate of plasmid loss during successive subculturings was greatest in the clone with the largest insert. The clone with the largest insert displayed a lower plasmid copy number than clones with a small insert or no insert at all. Plasmid loss in the form of segregational instability and plasmid copy number reduction in nonselective environments are important to the understanding of the evolution of the bacteria-plasmid associations and the appreciation of the potential for altering the genetic properties of a clone maintained or subcultured on a standard medium.Key words: pBluescript, plasmid, stress, fitness, starvation.

scholarly journals A High-Resolution View of Adaptive Event Dynamics in a Plasmid

2019 ◽  
Vol 11 (10) ◽  
pp. 3022-3034
Author(s):  
Han Mei ◽  
Barbara Arbeithuber ◽  
Marzia A Cremona ◽  
Michael DeGiorgio ◽  
Anton Nekrutenko
Keyword(s):  
Copy Number ◽  
Antibiotic Resistance Gene ◽  
Low Frequency ◽  
Plasmid Copy Number ◽  
Plasmid Copy ◽  
Host Chromosome ◽  
Adaptive Changes ◽  
Escherichia Coli Cells ◽  
Event Dynamics ◽  
Duplex Sequencing

Abstract Coadaptation between bacterial hosts and plasmids frequently results in adaptive changes restricted exclusively to host genome leaving plasmids unchanged. To better understand this remarkable stability, we transformed naïve Escherichia coli cells with a plasmid carrying an antibiotic-resistance gene and forced them to adapt in a turbidostat environment. We then drew population samples at regular intervals and subjected them to duplex sequencing—a technique specifically designed for identification of low-frequency mutations. Variants at ten sites implicated in plasmid copy number control emerged almost immediately, tracked consistently across the experiment’s time points, and faded below detectable frequencies toward the end. This variation crash coincided with the emergence of mutations on the host chromosome. Mathematical modeling of trajectories for adaptive changes affecting plasmid copy number showed that such mutations cannot readily fix or even reach appreciable frequencies. We conclude that there is a strong selection against alterations of copy number even if it can provide a degree of growth advantage. This incentive is likely rooted in the complex interplay between mutated and wild-type plasmids constrained within a single cell and underscores the importance of understanding of intracellular plasmid variability.

scholarly journals Segregational Drift and the Interplay between Plasmid Copy Number and Evolvability

2018 ◽  
Vol 36 (3) ◽  
pp. 472-486 ◽  
Author(s):  
Judith Ilhan ◽  
Anne Kupczok ◽  
Christian Woehle ◽  
Tanita Wein ◽  
Nils F Hülter ◽  
...  
Keyword(s):  
Copy Number ◽  
Plasmid Copy Number ◽  
Plasmid Copy

scholarly journals Plasmid copy number noise in monoclonal populations of bacteria

2010 ◽  
Vol 81 (1) ◽  
Author(s):  
Jérôme Wong Ng ◽  
Didier Chatenay ◽  
Jérôme Robert ◽  
Michael Guy Poirier
Keyword(s):  
Copy Number ◽  
Plasmid Copy Number ◽  
Plasmid Copy

scholarly journals Effects of Biofilm Growth on Plasmid Copy Number and Expression of Antibiotic Resistance Genes in Enterococcus faecalis

2013 ◽  
Vol 57 (4) ◽  
pp. 1850-1856 ◽  
Author(s):  
L. C. Cook ◽  
G. M. Dunny
Keyword(s):  
Antibiotic Resistance ◽  
Enterococcus Faecalis ◽  
Resistance Genes ◽  
Copy Number ◽  
Antibiotic Resistance Genes ◽  
Plasmid Copy Number ◽  
Plasmid Copy ◽  
Rapid Reduction ◽  
Biofilm Growth ◽  
Content Type

ABSTRACTBiofilm growth causes increased average plasmid copy number as well as increased copy number heterogeneity inEnterococcus faecaliscells carrying plasmid pCF10. In this study, we examined whether biofilm growth affected the copy number and expression of antibiotic resistance determinants for several plasmids with diverse replication systems. Four differentE. faecalisplasmids, unrelated to pCF10, demonstrated increased copy number in biofilm cells. In biofilm cells, we also observed increased transcription of antibiotic resistance genes present on these plasmids. The increase in plasmid copy number correlated with increased plating efficiency on high concentrations of antibiotics. Single-cell analysis of strains carrying two different plasmids suggested that the increase in plasmid copy number associated with biofilm growth was restricted to a subpopulation of biofilm cells. Regrowth of harvested biofilm cells in liquid culture resulted in a rapid reduction of plasmid copy number to that observed in the planktonic state. These results suggest a possible mechanism by which biofilm growth could reduce susceptibility to antibiotics in clinical settings.

Sign in / Sign up

Export Citation Format

Share Document