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Plasmids

Plasmids

Plasmids are extrachromosomal DNA molecules found in bacteria, archaea, and some eukaryotic microbes like yeast. These small, circular DNA structures typically contain fewer than 30 genes, although some may exist linearly. Plasmids vary in their number within a cell, known as copy number. Single-copy plasmids are present in one copy per cell and multi-copy plasmids are present in multiple copies, reaching over 100 copies per cell.Plasmids usually replicate independently of the chromosomal DNA...

Bacterial Transformation

Bacterial Transformation

In 1928, bacteriologist Frederick Griffith worked on a vaccine for pneumonia, which is caused by Streptococcus pneumoniae bacteria. Griffith studied two pneumonia strains in mice: one pathogenic and one non-pathogenic. Only the pathogenic strain killed host mice.
Griffith made an unexpected discovery when he killed the pathogenic strain and mixed its remains with the live, non-pathogenic strain. Not only did the mixture kill host mice, but it also contained living pathogenic bacteria that...

Antibiotic Selection

Antibiotic Selection

Genomic DNA in Prokaryotes

Genomic DNA in Prokaryotes

The genome of most prokaryotic organisms consists of double-stranded DNA organized into one circular chromosome in a region of cytoplasm called the nucleoid. The chromosome is tightly wound, or supercoiled, for efficient storage. Prokaryotes also contain other circular pieces of DNA called plasmids. These plasmids are smaller than the chromosome and often carry genes that confer adaptive functions, such as antibiotic resistance.
Genomic Diversity in Bacteria
Although bacterial genomes are much...

Genome Size and the Evolution of New Genes

Genome Size and the Evolution of New Genes

While every living organism has a genome of some kind (be it RNA, or DNA), there is considerable variation in the sizes of these blueprints. One major factor that impacts genome size is whether the organism is prokaryotic or eukaryotic. In prokaryotes, the genome contains little to no non-coding sequence, such that genes are tightly clustered in groups or operons sequentially along the chromosome. Conversely, the genes in eukaryotes are punctuated by long stretches of non-coding sequence.

Transduction

Transduction

Among the three main modes of HGT—transformation, conjugation, and transduction—transduction is unique in that it is mediated by bacteriophages, or bacterial viruses.Transduction occurs in two ways. Generalized transduction occurs during the lytic cycle of a bacteriophage infection. In this process, bacteriophages infect bacterial cells, replicate within them, and ultimately cause cell lysis, releasing newly assembled virions. Occasionally, random fragments of the bacterial genome...

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Related Experiment Video

Updated: Dec 6, 2025

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

Plasmid evolution.

Tanita Wein¹, Tal Dagan¹

¹Institute of Microbiology, Kiel University, 24118 Kiel, Germany.

Current Biology : CB

|October 6, 2020

Summary

This summary is machine-generated.

Plasmids are crucial genetic elements in prokaryotes, driving evolution through DNA transfer. These versatile molecules are essential tools in genetic engineering, biotechnology, and medicine.

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Last Updated: Dec 6, 2025

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

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Published on: December 14, 2019

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Plasmid Stability Analysis with Open-Source Droplet Microfluidics

Plasmid Stability Analysis with Open-Source Droplet Microfluidics

Published on: December 27, 2024

Area of Science:

Microbiology
Molecular Biology
Genetics

Background:

Plasmids are extrachromosomal genetic elements that replicate within prokaryotic cells.
They play a significant role in prokaryote evolution by facilitating lateral DNA transfer and mediating microbial interactions.
Plasmids are integral to understanding microbial adaptation and inter-species communication.

Purpose of the Study:

To highlight the evolutionary significance of plasmids in prokaryotic populations.
To underscore the diverse applications of plasmids as vectors in various scientific and industrial fields.
To emphasize the broad impact of plasmids beyond microbial evolution.

Main Methods:

Review of existing literature on plasmid biology and function.
Analysis of plasmid roles in microbial evolution, including lateral gene transfer.
Compilation of current and potential applications of plasmids in biotechnology, medicine, and agriculture.

Main Results:

Plasmids are key drivers of prokaryote evolution and microbial warfare.
They serve as indispensable vectors for genetic engineering in research.
Plasmids have wide-ranging applications in biotechnology, synthetic biology, agriculture, and medicine.

Conclusions:

Plasmids are fundamental to prokaryotic evolution and adaptability.
Their utility as genetic vectors extends across numerous scientific and technological domains.
Plasmids represent a cornerstone of modern molecular biology and its applications.