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Daily Transfers, Archiving Populations, and Measuring Fitness in the Long-Term Evolution Experiment with Escherichia coli
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Daily Transfers, Archiving Populations, and Measuring Fitness in the Long-Term Evolution Experiment with Escherichia coli

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Fitness costs of various mobile genetic elements in Enterococcus faecium and Enterococcus faecalis

Irina Starikova1, Mohammed Al-Haroni, Guido Werner

  • 1Department of Pharmacy, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway.

The Journal of Antimicrobial Chemotherapy
|July 9, 2013
PubMed
Abstract

Insights

Newly acquired mobile genetic elements (MGEs) can impact bacterial fitness. However, the biological costs of vancomycin resistance plasmids in Enterococcus species are rapidly mitigated during continuous growth.

Area of Science:

  • Microbiology
  • Genetics
  • Evolutionary Biology

Background:

  • Mobile genetic elements (MGEs) play a crucial role in bacterial adaptation and evolution.
  • Understanding the fitness consequences of MGE acquisition is vital for predicting bacterial spread and adaptation.

Purpose of the Study:

  • To determine the fitness effects of newly acquired MGEs in *Enterococcus faecium* and *Enterococcus faecalis*.
  • To test if the biological cost of vancomycin resistance plasmids is mitigated during continuous growth.

Main Methods:

  • Conjugation assays to transfer MGEs (conjugative transposons, pathogenicity islands, vancomycin resistance plasmids) into *E. faecium* and *E. faecalis*.
  • Experimental evolution of vancomycin resistance plasmids through serial transfer assays.
  • Fitness cost estimation via head-to-head competition experiments.

Main Results:

  • The fitness cost of newly acquired pathogenicity islands and conjugative transposons was dependent on the host and insertion site.
  • Newly acquired vancomycin resistance plasmids significantly reduced host fitness (25%-27%).
  • These fitness costs were rapidly mitigated within 400 generations of continuous growth without antibiotic selection.

Conclusions:

  • Newly acquired MGEs can impose an immediate biological cost on *Enterococcus* species.
  • The initial fitness costs associated with MGEs, such as vancomycin resistance plasmids, can be mitigated over time.
  • Beneficial plasmid-host associations can emerge rapidly during bacterial growth.
Keywords:
PAITn6000Tn916adaptationantimicrobial resistancedirectional selectionhorizontal gene transferplasmids

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