Order of authorship in the original publication: Dussoix, Arber. The authors discovered that restriction of DNA from infecting bacteriophage was due to the attack and breakdown of the modified bacteriophage's DNA by specific enzymes of the recipient bacteria. This was a key development in understanding the restriction modification system (RM system).

Order of authorship in the original publication: Linn, Arber. Arber announced the discovery, with proof, of the first restriction endonuclease (restriction enzyme or restrictase)."These enzymes are found in bacteria and archaea and provide a defence mechanism against invading viruses.^[4][5] Inside a prokaryote, the restriction enzymes selectively cut up foreign DNA in a process called restriction digestion; meanwhile, host DNA is protected by a modification enzyme (a methyltransferase) that modifies the prokaryotic DNA and blocks cleavage. Together, these two processes form the restriction modification system.^[6]"

Digital facsimile from PubMedCentral at this link.

(Thanks to Juan Weiss for this reference and its interpretation.)