Plasmids 101: Brief history Flashcards
How did plasmids get their name
In the 1940s and 50s, scientists were working to understand genetic cytoplasmic factors that could be transferred between cells. In 1952, Joshua Lederberg set out to clarify the classification of these cytoplasmic inheritance factors. He proposed the catch-all term “plasmid” derived as a hybrid of “cytoplasm” and “id” (Latin for ‘it’), as “a generic term for any extrachromsomal hereditary determinant.”
How quickly was Lederberg’s term adopted?
His proposal, however, was basically ignored. A separate term, “episome”, defined as “a nonessential genetic element which could exist either
autonomously or integrated into the chromosome” was proposed a few years later by Élie Jacob and François Wollman and became the widely adopted name for these elements.
Why did the episome definition make sense and how was it overturned?
At the time, the use of episome seemed appropriate, especially since the
Fertility, or F-factor discovered by Ester Lederberg in 1952 was noted to integrate into the E. coli chromosome in some cases. This terminology held until the 1960s when scientists began to study
other extrachromosomal particles, particularly Resistance or R-factors. Like F-factors, R-factors could be transferred between bacteria via cell-to-cell contact; however, scientists noted that, unlike F-factors, the evidence did not support the idea that R-factors could integrate into the chromosome. Thus the term “episome” was eventually dropped and we’ve been using “plasmid” ever since!
Although discovered in the early 1950s, it took until the 1970s for plasmids to gain prominence in the scientific community. Why was this?
Prior to this, bacteriophage, especially lambda, was the tool of choice for
molecular biologists wanting to study bacterial genetics. This all changed thanks, in part, to a collaboration initiated at a Hawaiian deli in 1972. Using a deli napkin for paper, a small group of scientists concocted a wild idea of using the newly discovered EcoRI enzyme (and its predictable cut site) to develop the first plasmid “cloning” experiment.
