Q186. An antibiotic is (a) a chemical synthesized by a human cell against a microorganism (b) a chemical synthesized by a micro-organism against an-x other micro-organisms (c)a substance produced by blood cells against bacteria (d)a substance produced by blood cells against infection.
Antibiotics commonly are produced by soil microorganisms and probably represent a means by which organisms in a complex environment, such as soil, control the growth of competing microorganisms. Microorganisms that produce antibiotics useful in preventing or treating disease include the bacteria and the fungi.
