<human>:  Who discovered penicillin?
<bot>: That would be Alexander Fleming. He discovered penicillin in 1928. He was working at St. Mary’s Hospital in London, and he noticed that a mold that was growing on a petri dish had killed the bacteria that was growing on it. He named the mold Penicillium notatum, and he found that the mold could be used to make a substance that could kill bacteria.