Several micro-organisms are used for preparing medicines. Antibiotics are

medicines produced by certain micro-organisms to kill other diseasecausing micro-organisms. These medicines are commonly

obtained from

bacteria and fungi. They either kill or stop the growth of disease-causing

micro-organisms. Streptomycin, tetracycline, and penicillin are common

antibiotics. Penicillium notatum produces chemical penicillin, which checks

the growth of staphylococci bacteria in the body. Antibiotics are designed

to destroy bacteria by weakening their cell walls. As a result of this

weakening, certain immune cells such as the white blood cells enter the

bacterial cell and cause cell lysis. Cell lysis is the process of destroying cells

such as blood cells and bacteria.