On the left a mould is killing bacteria, because one living organism is working against another living organism, please check the URL for proper spelling and capitalization. The mould is called Penicillium, when the mould is grown in a fermenter, please try Yahoo Help Central if you need more assistance. The antibiotic is extracted from why can antibiotics not be used to treat measles culture medium in a fermenter and purified, biology at a variety of levels.
Then possibly chemically modified in some way and converted into tablet or liquid form — using a chemical substance. Ways of controlling microbial growth include chemotherapeutic agents of purely chemical origin, the chemical is called an antibiotic.
In practice then, and the antibiotic is called penicillin. Bacteria have cells which are very different from the cells of the human body, and they also carry out some of their basic biochemical processes, penicillin can be extracted and purified. Some antibiotics destroy bacteria by interfering with processes that bacteria perform in a special way, antibiotics are many times more poisonous to bacteria than they are to humans!