Plasmid
Japanese: プラスミド
Small circular DNA molecules that exist independently of the bacterial chromosome. They replicate autonomously and carry genes such as antibiotic resistance. Widely used as a fundamental tool in genetic engineering.
Plasmids are small circular DNA molecules existing independently of a bacterium's main chromosome. They replicate on their own and can carry genes for antibiotic resistance, toxin production, and more.
For bacteria, plasmids are like optional components—not essential, but advantageous for survival in specific environments. Plasmids can be transferred to other bacteria through conjugation, one of the main routes of horizontal gene transfer.
In genetic engineering, plasmids are indispensable as vectors. Inserting a target gene into a plasmid and introducing it into E. coli—this basic technique laid the foundation of modern biotechnology.
Plasmids are symbolic molecules demonstrating that biological evolution occurs not only within individuals but also between them.