In 2012, Jennifer Doudna, Emmanuelle Charpentier from the University of California, Berkeley, in Berkeley, California, and Umeå University in Umeå, Sweden, along with their colleagues discovered how bacteria use the CRISPR/cas 9 system to protect themselves from viruses. The researchers also proposed the idea of using the CRISPR/cas 9 system as a genome editing tool. In bacteria and archaea, researchers had found that CRISPR, which stands for clustered regularly interspaced short palindromic repeats, and CRISPR associated proteins, or cas, helped organisms recognize and silence the genetic material of viruses that have infected the cell before. In their experiment, Doudna, Charpentier, and their colleagues found how the specific molecules in bacteria can recognize and cut specific DNA sequences of invading viruses. Doudna, Charpentier, and their colleagues’ discovery of the CRISPR/cas 9 mechanism and proposal of using CRISPR/cas 9 for genetic editing led to the successful engineering of CRISPR/cas 9 as a novel method of editing genomes.

Between 1935 and 1937, Leonard Colebrook showed that sulfonamides, a class of antibacterial drugs, worked as an effective treatment for puerperal fever. Puerperal fever is a bacterial infection that can occur in the uterus of women after giving birth. At the time of Colebrook’s study, puerperal fever remained a common disease due to both the lack of hygienic practices in hospitals and a treatment for the disease. After successfully using Prontosil, a sulfanilamide, to cure a patient who was going to die from puerperal fever, Colebrook began experiments with the drug. He successfully treated patients with puerperal fever with sulfonamides, specifically Prontosil and sulfanilamide. Colebrook conducted the experiment from 1935 to 1936 primarily at the Queen Charlotte’s Hospital in London, England. After Colebrook’s success using antibacterial drugs in treating puerperal fever, use of antibacterial drugs became widespread in developed countries and, by the 1950s, it had made maternal deaths rare in those countries.