Complex sentence: In 1928, Alexander Fleming became the first to discover a natural antimicrobial fungus known as "Penicillium rubens" and named the extracted substance penicillin which in 1942 was successfully used to treat a "Streptococcus" infection.
Split into simpler sentences: In 1928, Alexander Fleming became the first to discover a natural antimicrobial fungus known as "Penicillium rubens". The substance extracted from the fungus he named penicillin and in 1942 it was successfully used to treat a "Streptococcus" infection.