Werner Arber was a pioneer microbiologist who was able to study and understand the way bacteria protect themselves and their DNA from phages; other microbiologists such as Linn and Smith contributed very much to these discoveries as well. Arber stumbled upon something he termed ‘restriction enzymes’, which were enzymes from the bacterial host that would protect the DNA from phage editing. He called this, Dynamic Host Controlled Restriction of Bacteriophages (Pray, 2008). Researchers working on phages before Arber noticed distinct phage behavior: they noted how phages seemed to have a preference for hosts, growing well in some and poorly in others. A phage’s lack of growth was said to be ‘restricted by its host’ (Luria & Human, 1952). Arber discovered that the phage’s own DNA had a direct affect on the phage’s success in a bacterial host. After being exposed to a certain bacterial strain, a phage’s DNA will either be modified, or remain the same. The phage with the modified DNA could possibly be protected from attack by the host’s enzymes; on the other hand, the phage whose DNA underwent no change would be immediately attacked and dismembered (Pray, 2008).The bacteria’s restriction enzymes cut the phage DNA, or, more specifically; enzymes called EcoB and EcoK cause the DNA breakage (Meselson & Yuan, 1968). Arber and another researcher also found another enzyme that would sever the phage’s foreign DNA, but not the host’s DNA (Pray, 2008); this discovery showed them how bacterial strains were able to dismember foreign DNA while still protecting their own from both foreign attack and self-attack. This enzyme was named Hindi II. In summary, bacteria use restriction enzymes (such as Hindi II) to protect their DNA by searching for and dismembering foreign DNA from bacteriophages. They rely on the restriction enzymes to recognize certain markers that they lay down on bacteriophage DNA, or the lack thereof.