Scientific study of microorganisms, a diverse group of simple life-forms including algae , molds , bacteria , and viruses .
Microbiology is concerned with the structure, function, and classification of these organisms and with ways of controlling and using their activities. Its foundations were established in the later 19th century, with the work of Louis Pasteur and Robert Koch . Since then, many disease-causing microorganisms have been identified and means of controlling their harmful effects have been developed. In addition, means of channeling the activities of various microorganisms to benefit medicine, industry, and agriculture have been discovered. Molds, for example, produce antibiotics , notably {{link=penicillin">penicillin . See also bacteriology , genetic engineering .