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Plasmids

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Related Experiment Video

Updated: Jun 12, 2026

Quantification of Plasmid-Mediated Antibiotic Resistance in an Experimental Evolution Approach

Quantification of Plasmid-Mediated Antibiotic Resistance in an Experimental Evolution Approach

Published on: December 14, 2019

Rethinking the plasmid paradox: when plasmid costs do not affect fitness.

Lucy Androsiuk^1,2, Shay Tal¹

¹National Center for Mariculture, Israel Oceanographic and Limnological Research Ltd., Eilat, Israel.

Frontiers in Microbiology

|June 11, 2026

Summary

This summary is machine-generated.

Plasmids can impose fitness costs on bacteria, but remain common. This study suggests plasmid costs may be masked when other cellular processes limit bacterial growth, not just the plasmid burden itself.

Keywords:

fitness growth-rate microbial evolution mobile genetic elements plasmid ecology plasmid paradox rate-limiting step

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Area of Science:

Microbiology
Evolutionary Biology
Genetics

Background:

Plasmids are abundant in bacterial communities despite often causing fitness costs.
The 'plasmid paradox' is traditionally explained by factors like gene transfer and fluctuating selection.
Existing explanations may overlook physiological constraints on how plasmid costs manifest.

Purpose of the Study:

To investigate why plasmids persist despite apparent fitness costs in bacteria.
To challenge the assumption that growth rate is always a direct proxy for fitness.
To explore how cellular bottlenecks influence the expression of plasmid-induced costs.

Main Methods:

Formalized cell division time based on multiple cellular module requirements.
Analyzed conditions where cytoplasmic biosynthesis vs. membrane synthesis limits growth.
Theoretically modeled the impact of plasmid carriage on bacterial fitness under different bottlenecks.

Main Results:

Plasmid costs are only evident when cytoplasmic processes are the primary growth bottleneck.
When other modules (e.g., membrane synthesis) limit growth, plasmid burdens are 'evolutionarily silent'.
Laboratory measurements of plasmid costs may overestimate their ecological impact due to optimized conditions.

Conclusions:

The expression of plasmid fitness costs is context-dependent on cellular physiological state.
Growth rate is not always a reliable proxy for bacterial fitness, especially in ecological settings.
Understanding growth-survival trade-offs is crucial for accurately assessing selection against plasmids.