Penicillin was the first naturally occurring antibiotic discovered (Prontosil, the first
chemical used to cure certain infectious diseases, had been discovered in 1933 but had
serious side effects). There are now more than 60 antibiotics, which are substances
that are produced by microbes and that fight bacteria, fungi and other microbes
harmful to humans - the word means against (anti) life (bio). Penicillin is obtained in
a number of forms from Penicillium moulds.