Are extrachromosomal dna molecules that are not part of the bacterial genome.

The plasmid is an extrachromosomal DNA molecule that is not part of the bacterial genome. Plasmids carry genes that benefit the survival of the organisms. For example, antibiotic resistance. The plasmid is transmitted from one bacterium to another through conjugation. Transfer of genetic material is the mechanism of horizontal gene transfer and plasmid are considered as part of mobilome, unlike viruses where plasmids are nacked DNA.

For plasmids to replicate independently with cell must possess stretch of DNA that acts as the origin of replication. Self-replicating of the plasmid is called replicon.