EcoRI is a name related to which bacterium?

Correct answer: Escherichia coli

The governing concept is restriction-enzyme nomenclature. EcoRI was isolated from the bacterium Escherichia coli, specifically the strain traditionally represented in its name. The first letter, E, refers to the genus Escherichia; the next two letters, co, refer to the species coli; the Roman numeral I indicates that it was the first restriction enzyme identified from the relevant strain or source system. Therefore option A, Escherichia coli, is correct. Rhizopus and Agaricus are fungi, while Spirogyra is a green alga; none is the bacterial source associated with EcoRI. The name is therefore a useful example of how restriction enzymes are named from their organisms of origin.