An extrachromosomal DNA molecule that confers on bacteria resistance to one or more antibiotics. It consists of two components: the resistance transfer factor (RTF) required for transfer of the plasmid between bacteria, and the r-determinants (genes conferring antibiotic resistance). R plasmids were first isolated from strains of Shigella dysenteriae that showed resistance to multiple antibiotics. See Chronology, 1960, Watanabe and Fukusawa.
Subjects: Genetics and Genomics — Chemistry.