Assertion : While working on Staphylococci, Alexander Fleming observed that Penicillium notatum inhibits the growth of the bacteria. Reason : This inhibiting chemical was commercially extracted and its full potential was established by Alexander Fleming.

Step-by-step solution

Alexander Fleming while working on Staphylococci bacteria, once observed a mould growing in one of his unwashed culture plates around which Staphylococci could not grow. He found out that it was due to a chemical produced by the mould and he named it Penicillin after the mould Penicillium notatum. However, its full potential as an effective antibiotic was established much later by Ernest Chain and Howard Florey.