Penicillin G

Penicillin is the drug that started the entire modern era of antibiotics. In 1928, Scottish scientist Alexander Fleming noticed that a stray mold growing on a forgotten petri dish had killed off the bacteria around it — but he couldn't figure out how to turn that observation into an actual medicine. That breakthrough came over a decade later, in the early 1940s, when a team at Oxford led by Howard Florey and Ernst Chain, with crucial production work by Norman Heatley, worked out how to purify and mass-produce it; Fleming, Florey, and Chain shared the 1945 Nobel Prize for the discovery. Once inside the body, penicillin works by stopping bacteria from finishing construction of their protective outer wall — without it, bacteria burst apart from their own internal pressure, especially while trying to grow. Every related antibiotic on this site, including amoxicillin, still works this same basic way; penicillin is simply where it all began.