Final answer:
Alexander Fleming discovered penicillin in 1928 after observing a mold's antibacterial effects on a bacteria culture. The development and purification of penicillin were later advanced by Howard Florey and Ernst Chain, leading to penicillin's role as an essential antibiotic. The trio received a Nobel Prize in 1945 for this groundbreaking discovery.
Step-by-step explanation:
The discovery of penicillin was a significant milestone in the field of medicine. Scottish biologist Alexander Fleming discovered penicillin in 1928 when he noticed a mold growing on a culture of Staphylococcus bacteria. The mold, identified as Penicillium notatum, produced a substance that killed the bacteria present. Howard Florey and Ernst Chain later took up Fleming's discovery to isolate, purify, and test the effects of penicillin as an antimicrobial agent. In 1940, they reported success in mice, and subsequent human trials also showed effectiveness. The advent of penicillin as a clinically useful antibiotic played a pivotal role during World War II. In 1945, Fleming, Florey, and Chain were awarded the Nobel Prize in Physiology and Medicine for their contributions to the discovery and development of penicillin.