The letter R in EcoRI is derived from the name of strain.

EcoRI is a type II restriction enzyme that was first isolated from Escherichia coli strain RY13. The name EcoRI is derived from the genus name Escherichia coli and the strain designation RY13.

Strain designation in scientific nomenclature:
In scientific nomenclature, a strain designation is used to distinguish different variants or isolates of a particular species. It refers to a specific subtype or lineage within a species. Strain designations are commonly used in microbiology and genetics to identify and categorize different strains of bacteria or other microorganisms.

Escherichia coli strain RY13:
Escherichia coli is a species of bacteria commonly found in the intestines of humans and other animals. It is a well-studied model organism and has numerous strains that have been isolated and characterized.

Escherichia coli strain RY13 is one such strain. It was isolated from a clinical sample and has specific characteristics that distinguish it from other strains of E. coli. The strain designation RY13 helps to identify and differentiate this particular strain from other strains within the Escherichia coli species.

Isolation of EcoRI:
EcoRI was isolated from Escherichia coli strain RY13 by a group of scientists led by Hamilton O. Smith in the early 1970s. The researchers were studying the phenomenon of restriction and modification in bacteria, which involves the recognition and cleavage of foreign DNA by restriction enzymes.

During their experiments, they discovered a particular strain of E. coli that produced an enzyme capable of cutting DNA at specific recognition sites. This enzyme was named EcoRI, with "Eco" referring to the genus name Escherichia coli, and "RI" representing the strain designation RY13.

Significance of the strain designation:
The strain designation RY13 is significant because it indicates the specific strain of Escherichia coli from which EcoRI was isolated. Different strains of E. coli may have variations in their genetic makeup and biochemical properties, including the production of different enzymes. Therefore, the strain designation helps to identify and differentiate the source of the enzyme.

In the case of EcoRI, the strain designation RY13 is used in the enzyme name to indicate its origin and distinguish it from other restriction enzymes that may have different recognition and cleavage specificities.