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Updated: Nov 2, 2025
12:32
Quantification of Plasmid-Mediated Antibiotic Resistance in an Experimental Evolution Approach
Published on: December 14, 2019
14.2K
Evolutionary mechanisms that determine which bacterial genes are carried on plasmids
Sonja Lehtinen1, Jana S Huisman1,2, Sebastian Bonhoeffer1
1Department of Environmental System Science Institute for Integrative Biology, ETH Zürich Universitätstrasse 16 Zürich 8006 Switzerland.
Evolution Letters
|June 17, 2021
Summary
Bacterial gene location, especially for antibiotic resistance, is driven by positive frequency-dependent selection. Whichever resistance gene form appears first gains a fitness advantage, often leading to plasmid-borne genes being favored due to higher transfer rates.
Area of Science:
- Evolutionary biology
- Microbial genetics
- Mathematical modeling
Background:
- The evolutionary factors influencing bacterial gene location (chromosomal vs. plasmid) remain unclear.
- Antibiotic resistance genes are frequently located on plasmids, but the selective pressures are not fully understood.
Purpose of the Study:
- To investigate the evolutionary pressures determining bacterial gene location using mathematical modeling.
- To understand why antibiotic resistance genes are often plasmid-borne.
Main Methods:
- Mathematical modeling of gene location under varying selective pressures.
- Analysis of frequency-dependent selection and horizontal gene transfer dynamics.
Main Results:
- Gene location is under positive frequency-dependent selection, favoring genes that increase in frequency.
- This selection mechanism allows moderately beneficial genes, like antibiotic resistance, to persist on plasmids despite potential loss.
- Higher horizontal transfer rates for plasmid-borne genes favor their prevalence.
Conclusions:
- Positive frequency-dependent selection and horizontal gene transfer explain the prevalence of moderately beneficial genes on plasmids.
- The widespread sharing of genes across species amplifies this effect, favoring plasmid location for antibiotic resistance genes.
- This model provides insights into gene flow dynamics and plasmid persistence.
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