Step 1: Understanding the Concept:
Bacteria face constant attack from bacteriophages that inject their own DNA into the bacterial cell. To defend themselves, bacteria evolved a pair of enzymes working together: one that cuts up any foreign DNA that enters the cell, and one that chemically marks (methylates) the bacterium's own DNA so its own cutting enzyme leaves it alone.
Step 2: Key Approach:
The cutting enzyme in this defense pair is what we now call a restriction enzyme, because it restricts phage growth by chopping up the phage's DNA before it can take over the cell. Tracing where this pair was first isolated points to the answer.
Step 3: Detailed Explanation:
The first such restriction-modification enzyme pair was isolated from the common gut bacterium Escherichia coli, work that later earned Werner Arber, Hamilton Smith and Daniel Nathans a Nobel Prize once the cutting enzyme's precise, sequence-specific action was worked out. This discovery is also why so many restriction enzyme names begin with "Eco," short for Escherichia coli, such as EcoRI. Salmonella, Agrobacterium, and Archaea species are all sources of other useful enzymes in biotechnology, but they are not where this original restriction-modification pair was isolated from.
Step 4: Final Answer:
The two enzymes that restrict phage growth were first isolated from Escherichia coli, so option 3 is correct.