What is the zone of inhibition?
A zone of inhibition is a region on an agar plate in which no microorganisms are growing. The size of a zone of inhibition is often used as an indication of the effectiveness of a type of antibiotic against a particular type of microorganism.Normal DistributionWhen microorganisms, such as bacteria, are on a laboratory dish they usually form colonies, circular clumps that grow outward. Eventually, under normal circumstances, the entire dish will be covered with bacteria.Zone of InhibitionSometimes, however, other chemicals may be present on the dish, preventing microorganisms of a particular type from growing in an area. This area is called a zone of inhibition, because it inhibits bacterial growth.AntibioticsWhen testing the effectiveness of antibiotics, a paper circle soaked with the antibiotic is placed on a bacteria-covered dish. If the antibiotics are effective against the type of bacteria, a zone of inhibition will form around the circle. By measuring the width of the zone, the su
