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Updated: Jul 1, 2025
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Quantification of Plasmid-Mediated Antibiotic Resistance in an Experimental Evolution Approach
Published on: December 14, 2019
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Plasmid-free cheater cells commonly evolve during laboratory growth
Amber M Bedore1, Christopher M Waters1
1Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA.
Applied and Environmental Microbiology
|March 6, 2024
Summary
Antibiotic resistance genes on plasmids can be lost during bacterial experiments, even with antibiotic selection. This plasmid loss, especially on surfaces, creates mixed cell populations and can affect research results.
Area of Science:
- Microbiology
- Molecular Biology
- Bacterial Genetics
Background:
- Antibiotics are crucial for selecting and maintaining plasmids in laboratory settings.
- Plasmids carry antibiotic resistance genes, conferring a selective advantage to host bacteria.
- Antibiotic resistance mechanisms can act as public goods, benefiting neighboring cells.
Purpose of the Study:
- To investigate how antibiotic resistance mechanisms impact plasmid stability in bacteria.
- To understand the consequences of plasmid loss on experimental outcomes in microbiology.
Main Methods:
- Studied plasmid maintenance in multiple bacterial species under antibiotic selection.
- Compared plasmid stability in surface-grown versus liquid cultures.
- Examined resistance mechanisms including beta-lactamases, aminoglycoside phosphotransferases, and tetracycline antiporters.
Main Results:
- Plasmid-encoded beta-lactamases led to significant plasmid curing in surface-grown bacteria.
- Plasmid loss was also observed with aminoglycoside phosphotransferase and tetracycline antiporter resistance mechanisms.
- Liquid cultures showed more robust plasmid maintenance but still exhibited some plasmid loss.
Conclusions:
- Antibiotic selection does not guarantee perfect plasmid maintenance, particularly in surface cultures.
- The evolution of plasmid-free cells creates heterogeneous bacterial populations, potentially confounding experiments.
- Researchers must consider plasmid instability when using plasmids as tools in microbiology.
