How Did Alexander Fleming Kill The Bacteria

Alexander Fleming was a German botanist, biologist, and pharmacologist who discovered the first antibiotic. He did this through a rather extraordinary happenstance. While working with the properties of the bacterium staphylococcus he left on vacation. When he got back and was cleaning out his work area he noticed that a few of the slides he’d been working on had been contaminated by fungus. Upon noting that the staphylococcus colonize bordering the fungus had died he began asking more questions. Namely what was it about the fungus that caused it to kill the bacteria?
Through more research he was able to single out a substance that the fungus was producing as the result of its biological processes. He called this substance “mould juice” for